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Wednesday 15 November 2017

Tannoy SFX5.1 Powered subwoofer repair.

Paul popped by.

"I've got this Tannoy subwoofer, it crackles and pops. Can you take a look?"

Yeah - why not......


It's a smallish cube, mounted on little cones, with a downward facing speaker...

I powered it up, and all was quiet. 

Just as I was about to connect the signal generator, I heard thunder in the distance .... and it got louder and louder! The speaker was popping and crackling alright. I quickly powered down.

I removed the screws around the outside of the rear panel, to reveal the speaker. The electronics and amplifier are mounted on the rear panel itself....

The main amplifier, a TDA7293 is heatsinked to the rear panel.










Removal of the board showed signs of distress....

Q151 and Q152 and there associated components had been running rather warm! The colour of the cases of the transistor should be black, you can see in the photo that they've changed to a sort of powdery brown.

Q151 is a 2S1815, NPN, and Q152 is it's complementary PNP, a 2SA1015.











Static testing on the transistor tester showed both to be fine. But the fault seemed to exist only when the thing was drawing current, so I threw caution to the wind and replaced both transistors. The two diodes, the two resistors and the caps all tested within tolerance.







Switch on again, and it's cured!

In the above picture, you can see two wire links across F152 and F153, where there was place for a couple of fuses. The wire links are original, so the fuses were obviously deemed unnecessary, relying on the non-replaceable thermal fuse in the transformer...

Not sure I like that idea much....



*** STOP PRESS *** 12th May 2020.

Many, many people visit this site to look at this page, and, sadly can't find the correct transistors. 

The SCA1015 is obsolete, a KSA1015YTA is still available..  https://uk.rs-online.com/web/p/bjt-bipolar-transistors/8064403. You can try a BC556, but you need to fit it backwards, and reverse pins 1 & 2 (Check the datasheets)
The 2SC1815 is still available from mouser, or you can fit a BC546, again reversing the leads. (Check the datasheets).

These transistors are pushed hard in this application. When (if) I ever see another one, I'll look for a better solution. 

*** STOP PRESS *** 13th January 2021.

PeterCB has been working on his subwoofer, and replaced the 2SA1015 with a TIP32, and the 2SC2818 with a TIP31.

"So I went ahead and replaced the transistors with TIP31C/32C in a TO220 package. Been soak testing for about six hours now, they don't even get warm. The new transistors fit perfectly in place of the originals, just facing the opposite way, see picture"


This has got to be the best solution. An easily available transistor, that's not being pushed beyond it's limits. 

Thanks PeterCB! 

*** STOP PRESS 15th March 2021 ***

Avid reader Springknees has kindly created a schematic of the offending power supply section. 

It can be found at https://www.chantrybarn.co.uk/woofer.php and is reproduced here with permission. 









175 comments:

  1. I found similar problems with the KEF PSx000 series subwoofers and Celestion which were identical inside. Lots of electrolytics next to resistor dropper resistors. Several small transistors not doing what they should. Fitting proper regulators on big heat-sinks as well as the trannies worked wonders. Many electrolytics were replaced with high temperature ones. So far after a few years no returns... :-) Andy 2.

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  2. I have the same issue. I'll pop mine open and have a look!

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  3. Great post. Mine shows exactly the same heat problem. I'm more of a software guy these days, so what would you replace the diodes D151 and D152 with as I intend to replace ALL of the components around the scorched bit of PCB? I'm guessing something like 1N914.

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    1. Mine checked out OK. I think the scorching is caused t=by the transistors being faulty, rather than the diodes being poorly rated. They're nothing special, a 1N4007 or something would probably suffice...

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    2. Hello chaps, I have an SFX sub and have the dreaded thunder rumble and crackling noises when plugged into the mains (even with the coax disconnected). Other than that the sub works fine and even the auto switch on works. Would someone on here be willing to do a repair for me? I will obviously pay and also the return postage. I can just send the PCB or rear panel if easier. I live in Leatherhead, Surrey. Many thanks Gary

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    3. Gary here, just bit the bullet and replaced both transistors with the TIP31/32C and it's cured, they fit like a glove too. Definitely the best option. Thanks for this blog as I would have never known what to replace ☺️

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    4. Congratulations. Fabulous work.

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    5. Just done the TIP31/32 fix and it does indeed do the job. However my board was so scorched the traces are lifting so I had to get creative and solder them on the back side of the board. Seems to be fine and is working well.

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    6. Thank you. Just repaired my tannoy efx sub with tip31c/32c.

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    7. Thank you very for all the Info here about my Tannoy SFX .I replace with Tip31,Tip32 I even able to attach heat sink ,and I replace also 16v 100uf to 50v 100uf.And now I'm enjoying it.

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    8. Please can you help me or recommend someone that can repair my tannoy TFX from overheating

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    9. Maybe a location would help?

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    10. Done this repair seem to work but the extra heat burnt out the 2 resistors next to them r155-r152 so going to replace them and try again

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  4. Thanks for this post. I've just replaced my transistors, and my random distant thunder type noises have disappeared.

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  5. My Transformer also hums, and probably needs replacing. Is there a compatible transformer available?

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    1. Measure it's output voltage underload , and get something sutably sized from your local RS/Farnell etc ... I doubt Tannoy supply parts, but maybe worth a go. Note if you are fitting a replacement transformer, you must provide some protection fuses, as a replacement is unlikely to have the same protection built in as the original.

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  6. Hi Andy

    In regards to your comment about the wire links across F152 and 153, what fuse amp ratings would you replace the wire links with. I have the same fault that I'm fixing and think that protecting with 2 fuses is the way to go.

    Thanks for your super-helpful post, I eagerly await your reply!
    :-)

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    1. A wise move. I'd measure the current under load, double the measured value, and use a time-lag fuse to cope with the inrush to the caps.... As a guess 1.5A?

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  7. My mate switched voltage on back of sub now won't turn on can it be fixed?

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  8. I suspect that will have killed the transformer, and probably some other damage. Check the output of the transformer.

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  9. Stumbled over this post as have had a similar issue and sure enough the transistor at 152 looks like it's run hot. Found a1015 transistors and C1815 on eBay. They the right replacements? Look right! Thanks!

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    1. Most manufactturers don't put the "2S" prefix on the device, so they are probably correct.... HOWEVER ... I don't buy transistors on eBay unless as an absolute last resort! I've had far too many fakes. Try to find a reputable supplier. RS/CPC/Farnell/Mouser/Digikey etc etc...

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  10. thank you. replaced a1015, C1815 - no issues so far.

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  11. Just a quick tank you for this post. I was having the same problem with an SFX set I recently picked up cheap. A nice easy fix and my bargain speakers are ready for a few years of abuse.

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  12. A huge thank you for this post, I bought this sub-woofer second hand and thought I had bought a lemon. The transistors or mine hadn't visibly change colour but after getting random cracks and noise with no inputs decided to swap them for A1015, C1815 from ebay and has been working perfectly ever since. Even with my terrible soldering!

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  13. Thanks for this. I'm another user who experienced the same issue and your blog saved my sub from undue replacement / expensive repair bill

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  14. Thanks so much for this Andy. Am a complete novice when it comes to soldering, but a few pence worth of transistors (and a bit of time and patience) and the intermittent thundering has been banished from my sub! Tips: If you're struggling to get the backplate off after removing the screws, just take the speaker out from the underside and put your hand inside to push the plate out. I also found that the white push-fit connector had been 'glued' into the socket, but was able to carefully scrape off the dried glue and gently work it free. Well worth disconnecting it, as it makes working on the board much easier (you'll want it as flat as possible). As previously commented, my part numbers were A1015 and C1815 (also from ebay).

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  15. Hi everybody! I had the same problem on 2 subwoofers , replaced the 2 transistors and they are back running again... the only problem i see on both is that i can't turn up the volume too much... i mean ~ 40 % with signal supplied from an Ipad is the maximum i can go without distorsions. Anything above this will make them sound very poor... I need to mention that i test just the subwoofer(no other speaker playing, so i listen just the bass), and it doesn't sound loud for me, it sounds quite low... Or do i have too many expectations from this subwoofer?

    Anybody which has this, can you please supply signal from a phone / tablet , rise the signal from the device to maximum, set the LPF to 1/4 or 1/2 of the stroke and then please tell me how much can you rise the volume until sound gets distorted? At this volume how is the bass(if you listen just the subwoofer)?

    Thank you all!

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  16. Thanks to this information I was able to repair my Tannoy 5.1 sub aswell. It was showing the same heat damage around this set of components. Replaced A1015 and C1815 with components from ebay, £1 for 10 transistors. Soldering was a little tight to get to but with an extra pair of hands was easy enough :)

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    1. Turns out my celebration was early :( After a couple of weeks the pops and thunder returned. Any suggestion what could cause this to recur would be gratefully received :) I haven't got around to replacing them again just yet in case it is something else causing the problem.

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    2. Replace them again, and see what happens. I won't buy semi-conductors from eBay. There are too many fakes out there.

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    3. Will give it a go later today :) It could be that they are junk, I had issues finding replacements from elsewhere :(

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    4. See the latest stop press!

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  17. Hello. I need a picture of the electronics component inside. My tannoy msub10 was burning some resistors, transistors etc on the circuit board and i can not be able to buy that components because i do not know wich one is. I need a macro picture from that!. Can you?

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    1. This isn't an msub10 ... ??

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    2. I know, but the components are similar on the board...that's what i see. The numbers of transistors correspond!

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    3. These are the only photos I have.

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    4. Still need images ???
      I have the same issue changed the transistors and 4 weeks later its started again..

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    5. See the latest Stop Press!

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  18. I too have this issue with the SFX sub and find the same deterioration on the pcb, but I am struggling to find the exact replacements transistors for this job, particularly for the 2SC1015. Whilst competent to desolder and replace these components, I am not so technically minded as to quite figure this part out. Does anyone have any suggestions?

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  19. I too have the SFX issue as above, with similar deterioration of the transistors, but I'm struggling to find exact replacements for these components, especially the 2SC1015. Whilst being competent to desolder and replace them, I'm not quite so technically adept at determining suitable alternatives. Can anyone help? I'm UK based and cannot find anything that looks similar on RS/Farnell sites etc. Thanks in anticipation

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    1. Ugh ... it appears to have vanished. May need to rely on the vagaries of eBay ... and I hate that ... https://www.ebay.co.uk/itm/2SA1015-2SC1815-Npn-Pnp-50V-0-15A-0-4W-Pair-or-Individually-5-10-20-50-Pcs/223535558475?hash=item340bc1ef4b:m:mNnYj7nSKgkbTC3h6NJDLEA

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  20. Wow - thanks so much! - and I even trawled ebay myself and found nothing. Sterling work! At least you can buy these in a quantity, so if there is a quality issue, you've got them on hand to replace.
    BTW - thanks for your excellent blog and all the tech information!!

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    1. You're welcome Dingo. I dislike buying components on eBay, there are so many fakes out there. Sometimes there's no option. Beings as these are only just obsolete, I'd hope they're OK. If this continues, I should get the Jaeger book out and find something to fit Good luck!

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  21. I'd just like to add my thanks. I was ready for chucking the speaker in the bin, but found this blog and for £1.98 and a bit of faffy soldering I fixed it.

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    1. Well done Nick, another saved from landfill !

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  22. Thanks for your extremely helpful posting. Saved my little sub!

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  23. Congratulations nelmdog! Feels good, doesn't it!

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  24. Great post, thanks for the help :)

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  25. Hi, I have the same speaker, Tannoy SFX, but I'm getting a russelling noise even when speaker not connected to anything.
    Could this solve it?

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    1. Only one way to find out.... Go for it!

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  26. Had the same issues, opened it up and traces/pads seem to be non existent around the transistors and peeling up on the capacitor next to it. The board very brown/black. In the case of this sort of damage is it a goner? The subwoofer is 8 years old at this point but still a shame they don't let you buy just this board as I'd feel so guilty dumping such a big speaker

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  27. Carefully use some bits of wire to replace the damaged traces... You can do it!

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  28. I will give this repair a try as my subwoofer has started to make random thunder sounds.

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    1. Hi, I don't suppose you live around the Yorkshire area and looking for a little job to do at the moment?

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  29. Same problem for me. The circuit board doesn't look happy at all. I'll be putting it on ebay with a link to this page so someone can have a go at the repair.

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  30. Hi Doz, I've lived without my sub woofer for about a year and a half now, until I found this post! I've decided to have a go at fixing it myself (nothing to lose) but am having trouble sourcing the 2SC1815 NPN and 2SC1015 PNP. Are you able to point me at somewhere I gat get them (where I don't have to buy in bulk)?

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  31. Ha, read deeper into the other comments and saw your eBay link, so have bought there! Thanks Doz.

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    1. Whilst I hate buying parts on ebay, due to the huge number of fakes out there, go for it, and good luck!

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  32. Same issue on my sub - failed transistors. Those two form a ±12v supply for the analogue board with LPF etc. but they regulate down from ±40v so they are under a fair bit of stress and working close to max power dissipation.

    I changed the 220ohm drop resistors for bigger wattage 560ohm to lighten the load on them and stood them off the board. IR thermostat showed them running cooler. So far so good but a switching regulator would be better.

    Poor design really.

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    1. Do you have a circuit diagram?

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    2. Yes, it is bad design error and fitting the recommended higher power transistors (TIP31/32C) will give a more reliable unit. Plus it’s easier to find them.
      Don’t be tempted to put in a std three terminal regulator though , unless it’s high voltage input (40V DC plus ripple)

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  33. I tried to replace the transistors you mentioned but damaged the board in the process. Can I change the whole amp ? I cant see any with the same connector. Is that a major problem? They seem quite cheap. Thanks

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    1. That's unfortunate. With a little engineering, I suppose you could fit a different circuit.

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  34. Hi, another rumbler here! Do you know if the KSA1015YTA is the same (or near enough) as the KSA1015? The former is in stock at Mouser, along with 2SC1815.
    Thanks for the clear explanation and pictures.
    Cheers
    Pete

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    1. That's the part I listed in the STOP PRESS bit ... looks good from where I'm sat! Good luck!

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    2. In fact, I ought to make that a bit clearer really...

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  35. Do you think it would be possible to bypass the internal amp with another one , still using the original inputs and the electronic crossover . Thanks Dave

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    1. The transistors that fail supply the LT to the x-over, so that would have to be dealt with first, but yes, anything's possible with a little engineering.

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    2. Thank you very much ... I'll probably buy a nobsound amp and run it off that ..

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  36. I have replaced these transistors twice now, and the issue keeps coming back. The second time I sat them far from the board in hopes that they wouldn't get so warm.

    Could it be poor quality transistors? I bought them from eBay before your "stop the press" addition. I would buy new from mouser but their delivery charges are crazy and farnell have a 200 piece minimum purchase!

    Any thoughts would be appreciated.

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  37. These transistors are for the crossover, yes? Is there a way to bypass the crossover to solve the problem? The signal from my av amp should already be suitable and therefore the crossover is not needed in this setup.

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    1. No, they're in the power supply. Albeit the power supply to the x-over. See what the output IC is, and get a datasheet for it. You could remove the two transistors, cut the track from the x-over and drop the audio from your amp straight into the output IC.

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    2. I'll take a look at that. Cheers.

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  38. I purchased a nobsound 100w sub amp from Ebay and it works brilliantly...given up trying to fix the tannoy amp . Poor components pused to their limits.

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  39. Hi, can you fix mine. Obviously not for free 😁👍

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  40. Does anyone know a replacement transformer.
    Mine's dead so I can't even check the outputs. TIA... Mart

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  41. Very useful site, my sub last night decided it was thunder time ! Taken apart as like pictured my transistors are burnt. Order pleased with Mouse, will update when they arrive and I have fitted

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  42. Stumbled across this page as I have the same sub (purchased second hand) with similar crackling/thunder problems. Used the parts suggested in the Stop Press addition and ordered from Mouser. As others have said the postage is pretty steep so I order multiples of each in case I needed to replace again.

    Unfortunately the previous heat abuse had de-laminated the PCB at the Q152 transistor and the two of the tracks fell away. As I didn't have any copper tape to hand I have just used bent the pins of the transistors and soldered to the corresponding components on the board. All seems to be working well so far. Guess only the test of time will tell...

    Thanks for this useful guide. I've manage to fix a nagging issue for not a lot of money. Very happy.

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  43. great! had exactly similar problem of random scary "pops" from this sub even with no signal. I ordered KSA1015YTA and KSC1815YTA plus replacements for all but the two big smoothing caps. Had to also repair some lifted/vanished PCB track which didn't make for photogenic soldering!

    didn't work first time but after inspecting carefully I found another dry/lifted joint on a resistor. Repairing this and I now have a decent sub again.

    keep up the good work!

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    1. Fantastic work! Well done. Another saved from landfill :)

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  44. Hi Doz, I have nearly the same sub the problem I have is the 800mA fuse keeps blowing I think the transformer has gone. But the problem I am having is finding a replacement as there is no specs of the transformer its identical to the one in your article. If the transformer was working I can then see what voltage the secondary side has and get one to replace it. Do you know the specs of the transformer I know it must be under 50v as the capacitors are 50v.

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    1. I'm sorry, I don't... several people have asked before. It needs someone with a working one to make a quick measurement.

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    2. Yeah I thought that might be the case, I will keep digging online and see if I can get some information on it. :)

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    3. I've slept on this... I think we can make an educated guess... the datasheet for the amplifier IC has examples using a +/-29V supply, so what's the betting that's what is used. so if we spec a 20 - 0 - 20 transformer at 80VA, I think you're in with a good chance. Let me know how you get on.

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    4. Incidentally, if you this route, I'd fit fuses in those places I mentioned in the original article, and another in the primary, as any replacement transformer is unlikely to have a thermal fuse fitted.

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  45. Thanks so much for this. Replaced the 2 transistors with some from https://www.ebay.co.uk/itm/2SA1015-2SC1815-Npn-Pnp-50V-0-15A-0-4W-Pair-or-Individually-5-10-20-50-Pcs/223535558475(couldn't stomach £16 postage from mouser) ... Even with my poor solder removal skills that took of part of the track ... No more thunder.

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  46. Hi man, can you remember what type of zener diodes are on this board?

    Cheers, Keith

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    Replies
    1. Sorry, no. Perhaps someone will read this and comment ... are they not marked?

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    2. Even with a jewelers loupe I cannot make them out 🤣

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  47. This comment has been removed by the author.

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  48. Hi Doz, thank you so much for providing this information. I have a question - since these 2 transistors perform a fairly basic function supplying the +- 12v to the crossover, would it be ok to substitute some general purpose transistors that can handle a bit more power, such as a TIP31/32? I guess that might need changing some resistor values, that is beyond my knowledge, what do you think, is it worth me trying putting in a TIP31/32 and see what happens? Thanks again, Peter

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    1. I've mentioned this in the comments above. When I get another in for service, I'll have a look. Haven't seen one for ages now...

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  49. So I went ahead and replaced the transistors with TIP31C/32C in a TO220 package. Been soak testing for about six hours now, they don't even get warm. The new transistors fit perfectly in place of the originals, just facing the opposite way, see picture here: https://imgur.com/a/ljqoSvJ
    Thanks again Doz for the guidance.

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    Replies
    1. Great work PeterCB ... I'll publish that up top if that's ok with you.

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  50. I replaced both transistors but my resistor R152 has burnt out. What resistor and where do I need to purchase as a replacement?

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  51. Hi doz, im a relative novice to this. I replaced both transistors and seemed to be fine for about a day, upon another look I noticed resistor R152 was burnt out and the transistor Q151 was getting very hot. What resistor do I need for R152? Is it a 220 ohm 1/2v 5%?

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  52. Looks like the stop press transistors cause resistor burn out. According to Tomtom. Is this going to cause the same problem for everyone?

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    1. Unlikely ... we need more info.

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    2. Looks like there's no problem with the Mod.. that's 3 people who have successfully fitted the larger transistors now, with no issue. I think the resistor cooking is due to a further fault.

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  53. I replaced with A1015 and C1815

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    1. Thanks for the update.I suspect you have a further fault, not much help I'm afraid. Are the transistors still OK?

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  54. Thanks very much for the clear and helpful information. Had the rumble and cutting out randomly. I replaced both transistors with tip31/32 as suggested and working perfectly. No rumble or cutouts so far. Less than £3 to repair. Well happy.

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    1. Well done! Another saved from landill!

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  55. I just did the TIP31/TIP32 mod and thought all was well. Cone was operating nicely, clean sound... then I noticed a nasty hot smell. The two new TIPs are also roasting hot so there must be another duff component, but without a circuit diagram it's hard to detect the problem, know what component/value to change, or whether just to give up and drop £200+ on a new sub... some of which also have the odd user review about making random rumbling noises!

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  56. Hi Andy - Many thanks for your blog, I eventually replaced Q152 with a CV7672 (equivalent to 2N2905A), which has a higher voltage/current specification and a different pin layout. While in the process, I drafted a schematic for the failing circuit - I included some voltage and current measurements that might be useful to anyone interested, it's available for download/printing at:-
    https://www.chantrybarn.co.uk/woofer.php

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    1. May I put your diagram up here somewhere? Obviously crediting you for the excellent work!

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    2. No problem - it's Open Source :)

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  57. Hi Andy - I've updated my schematic to correct a current value. I've also added a guess at part numbers for the zeners and my calculated power dissipations for Q151 and Q152. I also updated my webpage to include some thoughts on power dissipation and transistor selection.

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  58. Doz and Springknees thanks for your blog and schematic.After much annoyance with the SFX5.1 popping the cause is due under rated transistors as reported from your blogs. I found, from a reclaimed Epson printer board, a NPN/PNP pair of transistors and matched the transistors C5888 with Q151 and A2099 with Q152.
    Removed the back input control panel after removing the bass speaker and using a hammer and piece of wood to avoid touching any internal components.
    Removed Q151 & Q152 but found ground track’s flakey. Fitted replacement tx”s using fine gauge wire to fix tracks were necessary (not easy for 72 year old!!!?)
    Had power/ amplifier out of unit put dummy 8 ohm load on speaker cable (just in case) and applied mains. Checked + and - 12v all ok.
    Has been working for the last 6 hours NO POPPING.
    Thanks for for your blog and all your contributors.

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  59. I have just attempted to use an old Tannoy EFX sub which is behaving in just the manner you describe in this article.
    I'll replace the transistors just to see if that is the problem and if that is the case I'll also get a couple of fuses to replace the wires you describe.
    To clarify, you feel 1.5 amp will be ok?

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  60. Thanks for this blog - really useful. Using a multimeter I've identified that my Q152 is faulty. (The Q151 appears to test as ok). The code on the transistor reads: "A1015 GR11". I was a bit concerned about some of the comments mentioning that replacing with the TIP32 resulted in potential overheating of other components, so I was wondering about one this instead: https://www.ebay.co.uk/itm/161996813809?hash=item25b7c335f1:g:cmwAAOSw6Gte60Py
    However, the code on the photo is showing as "A1015 GR331". I've googled extensively but can find no information as to what the GR11 and GR331 mean. Is that number significant? Will the GR331 be a suitable replacement for the GR11?
    Thanks!

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    1. The problem with overheating was failure of other parts, probably the power amplifier itself. In no way does changing the pass transistors to TIP's cause failure, unless another part is already faulty. I don't buy parts on eBay, there are simply too many fakes. Don't just change one transistor, they are too marginal.

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  61. Thanks - that's reassuring. In that case I'll go with the TIP31C/32C as recommended. I hear what you're saying regarding eBay; however, you end up paying a lot extra on the other sites for a transistor that costs less than £1: £10 "handling charge" on Farnell, and £5 delivery charge on RS.

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    1. Well, after many hours spent trying to solder the TIP31C/TIP32C transistors in place, I've given up. There must be a knack which I don't have. I'm using flux-cored solder, but the solder still just rolls into balls, doesn't stick to the legs of the transistor, and now the tracks of the circuit board have lifted and broken too. If anyone has any useful tips as to how to do this I'd be grateful! Otherwise, I'm going to have to admit defeat.

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  62. Ugh. The trick to soldering is a touch of solder to the tip of the iron, then warm the leg of the transistor, apply solder to the leg of the transistor and not the iron. It'll then flow into the joint. If the tracks are screwed you'll need to repair them with bits of tinned copper wire. Reply to this with your email address (I'll not publish it) and let's see if we can get you back on the straight and narrow.

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  63. I bought this sony surround system off facebook market place, briefly tested and seemed ok, had its stored for 6 months while I sorted the room out. Came with the Tannoy 5.1 SFX system, now iv sorted the room and connected it all, I could hear thunderstorms when nothing was connected apart from power.

    Little googling and found this site - brilliant!!!
    Opened her up as described above and some nice brown marks on the board exactly as above.

    Just replaced mine with TIP31/32s. Turned it all on wondering what is going to happen and sounded ok. Sat here listening intently and then a gentle rumble rumble rumble started! Gutted sat her listen more and realised it was my bloody stomach rumbling dohhhhhhhhh.

    TIPs seemed to have done the job and my terrible soldering seems to be ok, considering i had tracks lift/break.

    I saw on a Youtube they changed out the smaller capacitors around it as well, is this worth all the hassle??

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    1. What you need there is a kebab... Certainly caps don't like being warm, although when I did this one they all tested fine, but that was some years ago now. Run with it for now.

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    2. Think i’ll do just that, rather than risk knackering up other tracks etc are least I have spare TIPs if needed in future

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  64. Devastated, the PCB tracks and pads are wrecked. I can't get hold of Tannoy to try and get a replacement. There are only about 20 components on the board. Would it be possible to re-create the board?

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    1. Most things are salvageable. I very much Tannoy would keep spare boards for something like this anyway. Anything is possible with time and effort.

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  65. Thank you for this post. Its very helpful. I replaced transistors for the same as original and sticked radiators on them. They get very hot anyway. Next time they get burnt i replace them for TIP as you suggest. Also i noticed when my sub is in off state it generates 0.5V dc on speaker wires and there's same voltage on transistors as in on mode. In on mode there's 0.0V on speaker wire. I think there's something wrong with it.
    Cheers from Poland

    Marek

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  66. Had the same issue but no power at all to it on closer inspection the circuit board looks similar to yours but burnt underneath, would I need to buy a thermal fuse as well or are they robust

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    1. They do cook with the heat from those underrated transistors. The thermal fuse is integral to the transformer, once that's gone open, it's game over I'm afraid.

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  67. Thanks so much for your blog, I bought a tannoy SFX with satellites off ebay and the sub was thumping like thunder, thought I'd wasted my money but thanks to this blog i've just completed the transistor replacement today, knackered the tracks a bit taking the old transistors out but managed to use the legs on the new TIP31/32s to bridge across to a component they are supposed to be connected to (my soldering is rubbish but it seems to work)
    I did have one question though when putting the whole thing back together - I took the whole board off the back plate and when putting back together was not sure where to put these clear plastic bits that were covered in some sort of white thermal paste / heat transfer compound. I assume these are supposed to provide some sort of electrical insulation between the main amp chip and the backplate? (so go in between the back of the chip and the plate?) but then wouldn't that affect the thermal conductivity? I also put some insulating tape around the metal bracket that holds the chip against the backplate, though this only comes into contact with the black casing of the chip which I'm pretty sure doesn't conduct. Anyway would welcome any input on this, i'm mildly concerned the chip might overheat if I have not put it back together right

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    1. I suspect you're talking about the insulating mica or rubber pads for behind the main amp, and you're right, it's essential it's there ... If you want to send me a picture or something to check, see the latest Discord post, I'm always checking to see if anything's going on in there (nothing yet, but it's early days)

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  68. About a year ago I did the original repair using transistors from eBay and all was good until about a month ago when the rumbling returned. I checked back here and saw the stop press so just replaced with the TIP31/32 which has worked perfectly so thanks for the info! However when I first did the repair it did not work and I was able to fault find with the aid of the circuit diagram to find that the -12v side had an open circuit track due to the desoldering. Fixed this by bending the legs over and soldering to the next component on the track. Fantastic blog thanks!

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  69. I have just performed this repair and seems to work well but I was initially confused by what to replace Q151 with as the article refers to it as 2S1815, then 2SC1815 and then 2SC2818! Just to make this simple for anyone coming to this for the first time you replace Q151 with TIP31 and Q152 with TIP32. Thank you for this great guide.

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  70. Thank you for this fix.
    My Q Acoustics 1000si developed a similar fault, and I stumbled upon this blog by pure chance. Upon taking it apart I found a small section of PCB showing signs of heat discolouration... turns out it's almost the exact same circuit, albeit in a different layout!

    On the 1000si, Q1 is an A1015 PNP (replaced with TIP32C) and Q2 is a C1815 NPN (replaced with TIP31C). I had a quick look over the datasheets and went for it - my sub is now working again as it should!

    I wonder how many other subs out there use the same flawed circuit?
    Thanks again.

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  71. I have a pair of these subwoofers running in parallel (OCD dictates one was just not balanced to look at despite being a commercial audio professional!) and came here back in 2018 to find this excellent article from Bez and completed the original fix replacing Q151 and Q152 with the identical parts. Sure enough 6-8 months later we're back in the thunder and crackling department but as we'd resigned the front room to occasional use whilst I was now firmly rooted in my office and studio upstairs the subs got turned off to silence them until I had more time. Great to see the two new Stop Press items and big props to PeterCB for finding the TIP31/32C pairs are a good replacement and Springknees for the schematic. I'm just about to attack them once more whilst on a bit of downtime from work. Probably do the caps and diodes at the same time and rework the tracks to be sure.

    Cheers everyone, Happy Christmas and a fab New Year!

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    1. Bez? From the Happy Mondays? ... who knew...

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  72. Just wanted to say Thanks for the info. I had this problem with my SFX 5.1 and not knowing that it was repairable, I was lucky enough to find a hardly used one to replace it. I then found an article which said to just replace Q152. I did this with an equivalent and put it in storage as the new one was running fine.
    The new one has finally got the bug so I put my original, repaired one back and it's working fine ... for now.
    I have just completed the job replacing Q151 and 152 with the TIP's. I did find that the original transistors were difficult to get out because the pins had been bent over prior to soldering! This caused track damage and I had to put in link wires to solve the problem so be careful when you attempt it.
    The newly repaired one is now on soak (just to make sure my efforts work with no problems). If all is OK, I'll fit it and replace the other with TIP's and put that one in storage just in case.
    Thanks again Doz and everybody who has contributed.

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  73. To follow on from my report above. I have now put the speaker with the TIP replacement transisters in place, connected up and set on 'Auto' as I always have it.
    It didn't seem to want to turn on at first and it seems that it needs a bit more of a base signal to get it to automatically turn on and I wonder if changing the transistors to the TIP ones has anything to do with that.
    I'll keep my eye (ears) on this as the days go on but any thoughts on this anyone?

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    1. This shouldn't change that at all, they are simply regulator pass transistors. I'd check they're regulating properly, and providing the correct +/- 12V and then start fault-finding from there.

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  74. Last follow on ... I promise :-))
    So, after some days running the fixed unit, it seems that all is working fine, it's me that's over sensitive, not the speaker that's undersensitive :-))) but thanks for your reply, Doz.
    I have now changed the transistors in my other unit, again having to make a track repair after finding this one with glue all over the soldering of Q151, took ages to finally get enough off to get the iron onto some solder to remove the thing, also bent pins on the original transistor making it difficult to remove. All is fine now with this unit too :-))
    All in all, I've repaired two units for a total cost of just under £13 (GBP). I bought a set of 5 of each transistor from RS and whilst the P&P seems a bit high at £4.95, it is next day service.
    Again, thanks to Doz and everybody else for your help and advice.
    Cheers everyone :-)))

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  75. Thanks for this Blog Doz,
    I had a faulty Q Acoustics 1000SI with very similar symptoms and the circuit board looked to be the same as the Tannoy so I thought I would give it a try.
    I found the transistors as part of a set of 50 on Amazon (cheap and next day delivery) and opened up the beast.

    Unfortunately, removing the old transistors destroyed the connections as the circuit board was so brittle it crumbled. I decided to mount the transistors on the back of the board at the nearest decent connection points.
    Not the prettiest repair job but... It Works!!!
    Another Sub saved from landfill!
    Thanks to you and all the contributors to the blog.
    Neil

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  76. Going to give the tip31/32 replacement a go this week. Can't wait to get rid of the pops.. wish there was a guide like this to fix my mission sub amp too

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  77. I've replaced with the tip 31/32 but can't get a signal now. Where should I begin troubleshooting?

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    1. Check for the presence of + & - 12V across C155 & C156

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  78. I'm a bit concerned about the TIP31/32 recommendation. These transistors certainly have an adequate power handling capability, but they are very low gain eg, a maximum hFE of 50. With the 4.7k resistor feeding the base of Q151/152 and a voltage drop across it of 30V, the maximum current through it is 30/4.7 mA = 6.4mA. With the maximum current gain of a TIP31/32 of 50, the maximum current output from the power supply will be 50x6.4 = 320mA. That corresponds to a maximum power output of 3.8W per leg of the supply. And that's with maximum gain; it could be much less.

    A better choice might be a TIP121/126 combination. These transistors have a similar power handling capability to the TIP31/32 but much higher gain - around 1000 - as they are Darlington pairs. Using these should remove any PSU power output limitations.

    That's what I'm going to try as replacements on my power supply.

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    1. It's only driving the pre-amp & filter stage. I would doubt it's pulling 3.8W of each leg.

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  79. You're absolutely right. I hadn't noticed that the output only went to the preamp pins! 🤪 Now mine will have a superstable 12V supply!

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  80. Thanks for this information, I replaced the old transistors with the TIP31C/32C and now have my sub working properly again!

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  81. The design of this Tannoy is a bit rubbish.. With power switch in the OFF position, sub still draws 10Watts from the wall (24/7). This 10 Watts is probably being dissipated as heat through those transistors (I did not check). Anyway, my AV receiver has a 12V trigger out which I use to feed a relay that turn on/off mains to the Sub. Now 0W drawn from sub when AV receiver is off or in standby so no heat being generated on sub pcb.

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    1. I think you're being very polite about the design! Good solution.

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  82. Like many who have posted on here, this thread has been very useful in repairing my Tanoy SFX5.1 which started it's pops and rumbles recently. Following PeterCB's suggestion of using TIP31/32 as replacment transistors I orederd some from RS (next day delivery) and performed the repair earlier today. So far everything seems to be working fine (should this change over the coming days I will update this post). Unlike some have mentioned, I seem to have been lucky, the old transistors came out easily enough using a fine tipped soldering iron and a solder sucker (desoldering pump) without any damage to the tracks, likewise the new components dropped straight in and soldered easy enough. It should be a moderately easy job for anyone wishing to perform the same repair. Thanks to Doz and PeterCB for the information (it's appreciated) and I wish anyone else suffering from the pops and rumble issues the best of luck in extending the life of your sub.

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  83. The comments just go on and on, great work and than you.
    I have a different problem of low output, even with both controls at max I would say the output is down by ~ 75% (no distortion)
    I have buzz tested from the input and compaired this to a different known good sub and my output is low.(buzz test = touch centre pin of phono input to get mains buzz)
    I did see someone else in the blog ask the same question but no reply.
    PS I have replaced the caps and have tested the transistors.
    Any help chap, thanks

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    1. I'm afraid I wrote this years ago now, and can't really help with your low gain fault. 1st off, check out the chantrybarn schematic and check the supply voltages are OK. I don't suspect that's the issue, but we need to start somewhere... it's then a case of tracing the signal through the PCB, seeing where it's not getting the required level. I'd suspect somewhere in the adjustable filter, but without it in front of me, I'm going to struggle a bit!

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  84. Hi. I know this post i from a while ago. I picked up one of these subs broken and fount your post and chose to do it myself. I managed to change the parts for TIP31c and TIP32c. The device didn’t turn on before I did this and now it does but it pops. I grabbed a cable and i can sometimes get audio out for about 5-10 seconds then it goes off (no popping or anything in between) I’m confused as to why? I used a 3.5mm mono Jack to single RCA on an android phone and my PS vita as it’s alls I had at hand to test with (iPhones now not having 3.5mm) the device and cable wasn’t touched but I tested it and it didn’t make a difference (just buying the cable today) I can’t seeing it being the issue

    I’m not an expert by any means with component level diagnosis (I’m learning still) would or should there be anything to check? All solder joints I made are perfectly fine and all grounds re attached firmly

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    1. Are you driving enough audio in to make the detection circuit operate? (you should be) I'd start by measuring the voltages on the power supply (see the chantry barn diagram) and go from there...

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  85. Fixed. You are fab - thank you for taking the time to publish this. Dad and 2 teenage boys very proud to have fixed another bit of kit, but couldn’t have done it without your kindness. Thank you

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    1. Excellent work. It's an act of kindness towards the planet. We can't keep throwing this stuff in landfill.

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  86. Hello all, I am looking to convert the audio output from my denon avr ( zone 2 speakers) to a line input for our hearing loop equipment in out village hall, any help would be great, or a simple one off the shelf if one available, I did look at the AUTOLEADS LINE OUTPUT CONVERTER from Halfords do you think this might be suitable

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    1. Yes! I've successfully used those before... BUT don't connect it AND a loudspeaker to the same output .. you can easily end up with a feedback loop... Cheapo ones on eBay are good too, and a cheap source of audio transformers!

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  87. Lennard de Vries2 August 2023 at 17:45

    We alsi had rumble. I changed the parts with tip31/32 combi. Pcb was loose and had to be rebuild but it works fine now. Thanks for the blog.

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  88. Another successful fix using the TIP31/32 replacements! It’s cured the random ‘booms’ coming from the sub. All thanks to this blog.

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  89. Thank you for this post. Managed to fix my Tannoy subwoofer. Board was quite burned, a lot of tracks needed repairing and one of the caps had leaked too. Liberal amounts of hot glue added to keep things in place. Replaced all the caps and the zeners on the board while I was in there. Hoefully it'll be good for another 15+ years now.

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  90. Thank you for publishing this page. Same issue with a Tannoy sub, £10 worth of components and practising some rusty electronics skills had it up and running again. All components in the PSU changes (caps, diodes, transistors replaced with the TIP31/32 etc).

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    1. Please could you point in the direction of where to buy these (idiot proof ideally). Many thanks

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  91. Thanks to this post I repaired my subwoofer. I used tip 31 and 32 as suggested. Works perfectly now.

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  92. Cheers for the post, used TIP's as suggested and it works great.

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    1. Hi I am keen to fix my sub myself, I can solder ok, I'm just not clued up with the electronics (I regret not doing this at school at even a basic level). I wondered if someone could please refer me to the components that I need on ebay. And then talk me through which components I need to swap with what on the board.

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  93. My sub does do a good job of replicating thumber and other pops and booms, but largely it's silent, so I am thinking this repair would be worth a go. I have soldered a fair bit with the simplest electronics, so I am not very clever with this stuff, and I wondered if anyone could give me an idiot proof link to where I can buy the components (sorry if I missed that info), many thanks in advance.

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    1. I've just south these from https://uk.rs-online.com/web/:

      STMicroelectronics TIP31C NPN Transistor, 3 A, 100 V, 3-Pin TO-220
      Stock no.:485-9755
      Qty:5


      STMicroelectronics TIP32C PNP Transistor, -3 A, -100 V, 3-Pin TO-220
      Stock no.:485-9777
      Qty:5


      Unless I'm very much mistaken, they are the ones suggested. Will have a go at some soldering when they turn up - and let you all know

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  94. Hi, Thank to everyone commented on this topic I was able to replace the taransisters with TIP31C/32C plus the capacitors made my old sub comeback into life again! But I have a new problem now as the sub stops working randomly. The sub pics the sub out and get switched automatically but doesn't give sound sometimes. No loose wires or terminals. I have checked the Base driver too. Appreciate your thoughts on this. Thanks in advance.
    KR
    Lalinda

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  95. Hi I have the Tannoy EFX subwoofer. It works perfectly for about 10 minutes, then get's quieter and quieter to a point where there is no sound coming from it. Does this sound familier to anyone? Thank you

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  96. Yet again my Subwoofer +/-12V transistors failed - always come back to this blog to fix it!! This time it failed at 3am - woken up with the whole house shaking 😱
    Will use TIP3x's this time.

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  97. This is the second time I've had to deal with this power circuit! First time I replaced all the electrolytics and the two transistors. Great idea about the uprated TIPs, and the schematic is a real help. I also found that the -ve zener was giving -8.5v - so had to replace that. Hopefully it won't wake us up at 3am with a full blast 50Hz again!!
    Antony

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  98. Another happy customer here, thanks to this blog. I had one of these subs that was crackling/thundering, when it was left on for a while. The two offending transistors were running at about 80-90 decrees C and had badly discoloured the PCB. I have replaced them with the suggested TIP3xC transistors and it is now on soak test. I was expecting to have to drill out the holes for the larger legs on the TO220 transistors, but they were fine as they were. They now run at about 50 degrees C. I'm still undecided regarding heatsinks on the transistors (belt and braces) and replacement of the smaller capacitors, which were near the hotter, original transistors. Chris

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