"Got this ruined Akai tape recorder. Do you think you can remove the amplfiers and turn it into to a couple of mono-blocks?"
Yeah, why not...
Edward turned up one complete tape deck , and another two amplifiers, which are almost identical, but badged "Roberts"
One of the Roberts amplifiers has apparently got a duff output transformer in it....
I didn't take a photo of Edward's, but it looked similar to the above, except it appears to have been dragged across a car park...
I removed the deck ...Levers are bent, spindles smashed :(
I also remove the amps, and set to work on a re-cap...
The Roberts unit has been severely got at. Someone's had a go at re-inventing the wheel. Parts are missing, it's been totally re-wired. The other has a damaged VU meter. It's decided to leave these.
Once the two other amps are re-capped, and permanently switched to "record" , enabling a line level input to be amplified, and output. It's only a single-ended EL84, so it's not expected to produce trouser-flapping levels of volume.I've added a couple of warm white LED's behind the grills on the front panel to illuminate our valves a bit..
Being of Japanese extraction, the whole thing was designed to run from 100VAC, so export units had a built-in autotransformer. This is removed from the case.
My friend Julian fabricated some nice enclosures from MDF.
... which I painted the underside, inside and rear panel black.
... and set about adding some veneer ...
A phono socket and speaker binding posts are added to each unit ...
Finally assembled.
Next the auto transformer is mounted into a small ABS enclosure.
Which feeds the required 100V AC to the amplifiers via 2 IEC leads.
All tested and ready to return home ...
How's it sound?
I'm surprised. It's not loud by any stretch of the imagination, but it has some real bass control, which is unusual given the tiny output transformer. Use some efficient speakers and enjoy!
You can also wire directly to the power xforrmers as they have 117v taps under the bell
ReplyDeleteSadly not in the UK...
DeleteHi, thanks for sharing the build. I wonder if you could help. I have the Akai M-8 and I converted it into the pre/power amp a while ago. It was working fine and I decided to get rid of the reel to reel section - cut the wires and thought I knew what I was doing but when I switched it back on - it buzzed and wasn't working correctly, so I quickly switched off and left it at that. Clearly, some of the wires that were going into the reel to reel should have been reconnected to something else.... Would you be able to offer any guidance? Thanks, Martin
ReplyDeleteDid you push both amps into record mode? There's a slide switch on the top of each amp chassis - originally operated by a lever from the reel to reel part.
ReplyDeleteHi, which capacitors did you replace?
ReplyDeleteRichard
All the electrolytic caps. Most measured poor ESR. Everything else was OK.
DeleteHey, I'm just wondering what you did to hook the original auto transformer up to the amps. I'm in Australia and facing the same issue. I'm following an American tutorial but am lost as I need to run the amps from 240v.
ReplyDeleteJust mounted the autotransformer in a small box, and connected it with IEC's... see above.
DeleteDo you live in Broom? Excellent cinema there ;)
DeleteHonestly I'm electrically illiterate and can understand how to wire up a plug directly to the amps in the guide I'm following, which works in their case as they're running 120v out the wall. But on the auto transformer I don't know which wires coming out are the active and neutral from the power plug. I don't have access to a multimeter at the moment and was hoping to just follow by pictures, which probably wasn't a good idea to begin with.
DeleteMy plan is to keep the two amps bridged to each other and just have one plug in the wall powering them both.
I'm just looking to know how exactly the auto transformer sits between the mains plug and the amps.
P.S never been to Broome in my life let alone Western Australia lol, stuck in Sydney for the time being.
Reply to this message with your email address (it won't be published), let's talk you down ..
Delete