ANDERSOUNDS

Audio Services - Edinburgh

[andersounds]

The MM is back again for some voice board renewal, down to the last two boards in top left pic, plenty old parts building up in the parts bucket, such a great sounding synth with some technically poor layout and design choices, scary but fun to work on, don’t fry the CEM’s!

Lower pic shows new ribbon cables installed, so begins the tuning process.

[andersounds]

Interesting vero board / stripboard build on this comp, the cabling was all over the shop, many caps were dead, but the biggest issue was the contact pins on the slots for the cards, they were making very bad contact causing jumpy signals.

also the power supply module was being fed by a dual 25v transformer, there was a hefty voltage coming out of the rectifier that would have fried the +/- 18v regulators, this was reduced with large 10w resistors to bring the voltage down to around 25v, swapped out the transformer for a dual 18v and did away with  the giant resistors, notice the burn marks from where the regs were mounted, still some room for improvement with the power supply, but it is cool and stable now.

[andersounds]

Is it sensible to service a moog voice board and SSL mixbus compressor boards all at the same time!?! who knows but they work so much better now. Check the ESR reading from the old cap that came from the SSL.

[andersounds]

A micro four thirds camera getting the shutter mechanism sorted.

Yes I got it back together with no leftover parts and it works ! :)

[andersounds]

THE DOG, having a snack in the spare parts box, I’m sure he is a static generator too.

[andersounds]

Yamaha CS-10 synth, had a 100v japanese transformer, picked up a 115/230 type fairly cheaply a great fit, much more roadworthy than the step down that was hanging off it.

[andersounds]

Boss Dr 55 clone build CB55 weekend project. had the parts you can see on the board in stock an easy build and good quality PCB from circuitbenders, only £10 for the board plus shipping, shipped pretty quick too.

hopefully it will work.

[andersounds]

If you have a MemoryMoog with a group of LEDs out, check the schematic as they are in blocks of four. Here OSC1 waveform selections were working but no LED illumination, also Return Zero was out, looking at the diagram it’s clear that either S61 ribbon cable is faulty or there’s a problem on the board, as the LEDs would work when the board wasn’t bolted in this suggested flexing of the board, a factory revision / track slash as pictured had overshot the intended track a little and cut in to the one above S61-13, probably been working ok for 35yrs, now the servicing has triggered the poor job on the board to cause this group of LEDs to fail. 

[andersounds]

AMS 15-80 Delay board getting some servicing, waiting on power supply capacitors for the next stage.

all the small capacitors in the 15-80′s are mostly 22uF 25v Tantallum, these have lasted a long time and hold value better than electrolytic’s but tantallums often short out when they fail and that isn’t a great failure mode, electrolytic’s on the other hand usually increase in resistance.

[andersounds]

Roland G800 dead power supply board. Main filter capacitor wasn’t soldered in properly, but this wasn’t the only fault, the transformer in the centre was shorted, usually end of days or a re winding, but don’t give up, on further inspection with the xfrmr removed could see that the winding’s that were shorted simply had fused together in an accessible area, parting the wires resolved the issue and got the G800 back on the road

[andersounds]

Fostex R8, in for mechanical servicing and adjustments, a well built compact 8-track.

[andersounds]

this isn’t how you expect capacitors to arrive in the post, myHermes though so not too surprised.

[andersounds]

The control panels also had a surprising number of inoperable buttons, usually a small amount of contact cleaner might revive them, not on this old moog. It required most of the metal contact strips to be de-soldered from the boards, once underneath the spring contact strip you can just see there’s a small centre contact that has a very small surface area, one mod could be to install a larger centre contact.. however this may not be a common problem?

Next on to tuning the oscillators and filter if I have the time. :)

[andersounds]

The memorymoog keyboard only had 3 or 4 keys working, usually you will see a few keys needing looked at, cleaned every contact and rubber pad and it was still only 70% had to go back a second time, either the leaked capacitor or nicotine had really gotten in there, probably both.

[andersounds]

Dreaded memorymoog fan, heavy, noisy, hot and generally not that great, however it is built to last and at the moment don’t have anything to replace it with, so why not at least see what can be done if it stripped down.

Orignally it was covered in gunk and rumbled like a fridge, so not great at all, after all the old oil and gunk was removed it at least doesn’t rumble and seems to spin faster! well it will live another day, a future upgrade will probably replace this as this 16W fan generates almost as much heat as the power supply..

[andersounds]

Got the capacitors and did the rebuild, voltages check out and can be trimmed to spec. next the control surfaces.

[andersounds]

Memorymoog first look, when powered nothing but a buzz, inside it is clear the notorious power supply had died, possibly spreading capacitor gasses around the insides, just the begging on this fairly complex polyphonic synth repair.