Sanyo TP1100 Turntable repair.

Colin rang...

"Got this Sanyo turntable here ... doesn't work, got a new Rega Carbon cartridge on it, but doesn't spin. Nice thing, heavy , all die-cast ... are you interested for £15?" 

Now, under normal circumstances, I would have taken Colin's arm off... but right at the moment, I'm planning a major workshop build, and if I bring anything else into the house, the current Mrs Doz is likely to serve divorce papers. I politely declined.

... time passed ...

Colin rang..

"Need a turntable for Fiona, sensible price.. have you got anything?"

"I haven't, but what about that Sanyo?"

"It doesn't work."

"No, but I'll see to that... "

So it arrives in top-secret, under the cover of darkness....

The turntable powers up OK, and moving the arm over should automatically start the platter. Nope, but the neon stroboscope lights up.... "The lights are on, but there's nobody home".

First off, remove the mat and platter, and place safely out of the way, then remove the screws from the edge of the blow-moulded bottom cover.

There's a DC controlled direct-drive servo motor, and some levers to automate the turntable. 

The simple DC controller is mounted to the impressive die-cast chassis, and is powered from a small transformer, well away from the arm end of the deck.

The turntable's power is controlled by two microswitches attached to a spring loaded lever at the base of the arm. 

The microswitch nearest us controls the power to the neon... The other switches the secondary from the transformer (about 20VAC) to the speed controller board. 

The neon works, but the motor doesn't, and a few checks prove the microswitch isn't working anymore. 

It's removed, and a replacement sourced. 

Unfortunately, the replacement is useless... It requires too much force to engage the switch. The spring on the lever is too weak, and with good reason, its triggered by a cam on the base of the arm... too much force here would be disastrous. 

OK, now a switch with low force is available, but not in that form-factor. Some head scratching ensues... The original (but broken) switch is refitted. The two yellow wires from the broken switch are shorted together, and tidied up. 

The transformer's feed from the LIVE side is disconnected and is now connected to the switched live side of the neon strobe... so when the neon's on, the transformer is connected, and it's output fed to the speed controller... 

... all is well. Almost. 

There's a *click* on the audio as the turntable starts up and stops. We'll have to live with that, until a suitable switch is obtained, anyway ...

Another saved from landfill! 

The turntable is tested with Nicky Thomas "Love of the common people"

Linn Lingo repair - won't change speed.

John from the cold north rang...

"Got a Lingo here, it's been serviced by someone here, but it's now stuck in 33 RPM. Care to take a look?"

Yeah - why not?

It's the first version of the lingo.

Off with the lid, and I can see some work's already been done. It's been recapped. The workmanship is good... or is it?

The original repairer was obviously proud of his work, as there's a signed sticker inside the unit. I've blurred this out to prevent embarrassment. 

Now the lingo is similar to other power supplies of this era from linn, they suffer with capacitor failure. Now you could upgrade your supply to the latest and greatest (don't forget kids, Linn ownership is all about upgrades, right?), or get it repaired. This has all new capacitors, of quality brand, so it should be good. It was only done in August last year (it's now January). Apparently 45 RPM hasn't worked since they had it back... 

So it's just stuck in 33. Pushing and holding the switch just causes the Red led to go from bright to dim repeatedly, and never get to 45. Great ... it's usually either U7 or U8, best to change both to avoid issues. It's a 74LS74. The best way to get them out is to cut off the legs, and remove each leg separately to avoid damaging the (as usual) fragile double-sided print. I get two new IC's and socket them. Powering back up, and switch to 45 , it briefly lights the green 45 RPM light, before dropping back to the original fault. Damn. 

Thankfully having socketed the IC's, I can remove them without damaging them, and test them in the sometimes useful DiagnoSYS IC tester (thanks Norm).

One is duff... double damn... was it a duff one out of the packet? I replace it, and promptly blow another. Triple damn. What's going on?

There's a bit of feedback from the motor drive amplifier on the lingo, so it knows when to turn the voltage down to the motor. This feeds U4, a 74LS221. It's removed , and a socket fitted. A new chip changes the fault slightly. Sadly the DiagnoSYS tester can't do 74LS221's..  Checking U7 again shows it hasn't failed again, so that's something. Out with the scope. There should be a ~5 second timing constant. Checking around, I find it. It's on pin 6 of U4... and is formed by C7 (220uF) and and R33 (56K) (those of you who have just got the calculator out, will inform me that that's 12 seconds, and yes, you're right, but it triggers the IC as it moves over the trigger threshold, of around half of the supply). The cap is obviously brand new, but is removed anyway and tested. It tests fine. But it's only 22uF. C7 and C9 have been reversed!! (now you know why I blurred the label!).

It's reassembled again, and this time works fine! 

"The person that never made a mistake, never made anything" 

Ahem.. 

Strathclyde STD 305D Display fault

Remember the Strathclyde STD 305D I built a supply for here? Well, it ran for a while then the display started to play up .... 

It stopped indicating the correct speed. Ugh.

I got it back into the workshop, and poked around the board. 

The vacuum fluorescent display is driven by a long obsolete counter, a Plessey ZN1040. The good news is, it's actually counting. The bad news is that's all it does. The way it indicates RPM is it counts some pulses derived from the motor's tachometer , and a reset pulse comes along and resets the count. The display is then updated on reset, so 33 pulses per "reset" indicates 33 RPM on the display ... A prod round with the 'scope shows the reset pulse is missing. The pulse is generated from a Plessey ZN1034 precision timer IC, again long since obsolete. Damn. 

It's a bit like a posh 555 IC.. It's simply configured as a bistable. Replacements appear to be available on eBay, but are of questionable parentage. (You can't tell me that when this thing went obsolete in the early 80's, China had massive stocks of them).

We need to find another solution. 

This is a quick sketch of the relevant bit of the STD305D's schematic. 

As shown here, it's the Q output that feeds the reset pin of the counter. The complimentary output (not Q) of the ZN1035 timer is also feeding something, so we'll need to implement that also ..

 

The power supply available is 5V, so that's easy. How about an ATTINY85 ? Perfect. Two pins connected for both outputs, Q and not Q. Should be easy enough, and be easy to fit. Good, a plan. 

The program is simple enough ... 

#include <avr/io.h>

int timing = 1000;

void setup() {

  // PB 3 and 4 to output

  DDRB |= (1 << PB3);

  DDRB |= (1 << PB4);

}

void loop()

{

  //set PB3 , unset PB4

  PORTB = 0b001000;

  delay (timing);

  // set PB4, unset PB3

  PORTB = 0b010000;

  delay (timing);

}

I've used direct port manipulation to minimise the overlap between Q and not Q. digitalWrite takes longer to change the state of the port. I don't know whether that would be an issue in this application, but it's best practice. We can tweak the timing variable to suit.

The ATTINY85 is loaded into an adaptor and programmed using my ISP programmer. 

As power consumption isn't an issue, the micro is set to run at 16MHZ internal clock. 

The ATTINY85 is pressed into service, and produces odd results. The reset line still isn't resetting the ZN1040 counter. Checking through, I connect it directly to the reset line of the ZN1040 ... not a good idea, as this instantly kills the output pin on the TINY. :(

Liberating the ZN1040 pin from the board, the pin on the IC measures a few ohms to ground. Not only is our ZN1034 dead, but so is the ZN1040.... What's common here? Ugh , the +5V rail. 

I measure the 5V rail ... it's 5.1V , close enough.... hang on 5.2 .... 5.3 ... it ends up at 6V , the regulator on the power supply board is shot. It's a simple enough Zener diode and transistor affair... I sack it off, remove the BD239 pass transistor, and fit a 7805 on a heatsink. It's all a bit too late for our poor ZN1034 and 1040 though. 

So what to do? Obviously remove both IC's. Feed the pulses from the tacho into an arduino, calculate the speed, and output it over the existing discreet transistor drive circuitry to the display. Works for me. 

Studying the datasheet for the ZN1040 , gives us all the info we need... 

OK, so this is shown for LED displays, but the principle will be identical. Four lines switch on the supply to select which digit MSD (Most significant) to LSD (Least significant), only three are connected in our application ... We'll need to multiplex these, and the actual segment drives (A-G) need to be pulled low to illuminate the display. 

First up, is go get our arduino to read the pulses from the tacho. 

They should be arriving at pin 22...

... and, sure enough there's a nice negative going pulse train arriving, and it varies with the speed control. Great. 

We'll drop these pulses into INT0 on our arduino, and trigger an interrupt on a falling edge.

 

A quick piece of code is conjured up to read RPM and output over the serial interface. It's uncalibrated at present, but is near enough , reading 33, 45 and 78 RPMish...

Excellent, we can return to calibration later (the turntable is currently upside down with no platter on it).

Now to deal with driving the existing display. The ZN7040 is capable of muliplexing a 4 digit display. In this application only three digits are used. A quick bit of reverse engineering shows those digits are the 3 most significant digits. These are coupled to  our arduino on pins A1- A3 and set to digital outputs. Each of these pins feeds a grid, and taking this high allows the display to function.

Arduino pins 3 to 9 are connected to the segments drives for A through to G. These are used to individually control each segment's anode. Pulling the pin low, switches on the anode, and illuminates the segment. 

Bingo, a muliplexed display. Now to couple the two parts together...

And finally to reassemble and calibrate ...

Nice!

I will NOT be beaten by mere machinery!!

The software is available as usual from my github.

And another saved from landfill, these really are a stunning deck. 

Garrard Zero 100 Plinth cosmetics.

After the Zero 100 was repaired (here and here) I was left with a very tatty homemade plinth.

The plan is to tart it up and make it something that Mrs Doz will tolerate...

Let's remove the old existing veneer.

First up is to steam the veneer with a clothes iron, and a damp cloth. This should soften the glue. You can then start to work a knife blade under the veneer and slowly remove it. Try to work along the veneer, not splitting it, warming and working your way along as you go.

This veneer is obviously held on with some synthetic (rather than animal) glue, as it was quite tough. Nice thick veneer too... pity it was poorly done. This didn't aid removal!



So after a couple of hours work, we've not got a tatty plywood box. At least it's square...











Now I did consider some black and white plastic laminate, but initial experiments weren't very successful.. wood it is ... but I still want something "different" for a very different turntable...

I experiment with a strip of the available veneer, and some water based stains. I like the ebony, but a straw poll of Mrs Doz, and my neighbours, Suzie and Steve, and anthracite comes out top...

The stain comes from eBay seller letspack_uk , and comes as a small sachet you mix up with hot water, and allow it to cool before applying.





The plinth is veneered, and stained in 4 coats of the anthracite.











This is after 4 coats of stain, and 2 coats of finishing oil with many more to come! After each coat, the finish is flatted back with some fine wire wool.

About 20 coats of finish are applied, carefully flatting back after each one. The result is a lustrous finish. 

The Turntable is mounted solid, as the suspension is missing it's foam dampers (probably long since rotted away), and unlikely to help. 

Rather pleased with the end product :)

"Linn" Hercules II power supply

The continuing story of the LP12 .... saints preserve us ...

This is an aftermarket thing (remember kids, Linn ownership is all about upgrades, right?), made to put two speeds on your Linn LP12, without all that tedious belt pulley swapping business...

Look familiar?



It's almost identical to a Valhalla, except it has some logic to switch between speeds like an Axis, and has two oscillators, and an analogue switch stuck before the pulse shaping, to change between the two oscillators.... oh and the print doesn't fall off when you touch it with an iron...

Anyway , this is my good friend Colin's, he's done the caps (and done a tidy job too), and it's still no good...

A quick check of the two crystal oscillators show they're both working, and so are the dividers. The output frequencies are 50Hz for 33RPM, and 67.5Hz for 45RPM. Both are present at the 4066 switch, and make it on through the pulse shaper , and are all fine at the output on pin 14 of U2 (again, sound familiar???) Everything goes pear shaped on the output driver at pin 8 though ....

Changing out U2 (an LM324 , instead of the LM2902 in a Linn supply) provides a cure.

Another Linny happy.... until the next upgrade....

Garrard Zero 100 from Hero to Zero (and back again) - Arm re-wire.

After successfully overhauling the mechanics of the Zero 100, I carted it in the lounge for a proper test.

All good ... a couple of LP's in and it loses the left channel. It comes back again.

Sunday morning, bacon sandwich. Beatles Rubber Soul. I return from the kitchen, coffee and sandwich in hand, and sit on the sofa, listening to the Beatles....

Funny, didn't think I had the mono press of this....

... and I don't.

Damn. Arm wiring.







Now I'm one of those odd people who actually enjoy arm wiring, but this could be a little daunting.
A quick google search chucks up loads of people who say it can be done, but it's very difficult neigh on impossible etc etc etc .....

Good, I like a challenge.

Cartridge Slide out first, and put it to one side, so we don't damage it.

Undo the gimbal housing screw and slide the gimbal housing down the arm and put that somewhere safe.








As there was no doubt in my mind that the wiring was at fault, I just cut it off ...











Slacken the arm bearing off, this will allow extraction of the arm.











OK so far ....












Removal of two screws allow the separation of the arm tube from the bearing support. There's a small grub screw at an angle, losen this to remove the plastic insulation "top hat" which the wiring passes through. I didn't do this at this time, and broke the wiring, not that that mattered.







I spent a few minutes looking at this, trying to work out how to get the headshell pivot apart.










Get a piece of blu-tak, and stick it over the pivot...











... and pull. Bingo, the small silver cover pops out, and reveals a small black plastic nut. Undo this, and don't lose the washer underneath it.










... And there's the wiring :)











The headshell is then removed, and four lengths of Litz wire prepared. Always allow for much more than you think you'll need. It easier to make it shorter ;)











A piece of teflon wire is used to pull the new new wire through the arm tube.











Out with the old ...













In with the new.












This is the angled grub screw I talked about earlier. Loosen this to remove that white plastic insulating "top hat".










Pass the new wiring through the insulator, and refit. The bearing support can now be re-attached to the arm tube.










My teflon wire is once again employed to pull the wiring through the centre of the gimbal.











Refit the arm, and nip the bearing up just enough to remove any play.











Refit the cartridge slide, with three wires diconnected, and, using a multimeter, identify each conductor. I use a coloured sharpie to mark each one.








and finally trim the leads, and solder them to the output connector.

The Beatles are now back in stereo (which is a pity tbh, the mono mix is far superior.)









Feet up, Sunday afternoon listening to The Blossoms.










Now, what about that plinth?