[sdiy] EMS Synthi AKS units: progress

[RMC]

Hello

Well, I've "re-capped"  the first AKS and got it 80% working. The envelope 
shaper did work but has now stopped, and the reverb has yet to spring into 
life (sorry).

I'm about to start on the second unit, at which point I'll be able to swap 
boards back and forth to see where the fault is, carry out comparative 
measurements. Thanks to people on these lists I have had a lot of help and 
offers of assistance for when I get stuck on the electronics and I want to 
thankyou for the various off-list email exchanges.

I've found a pair of TAB101s (Ge transistor rings used in the ring mod) and 
I'm hunting for MF7104s (shift registers used in the KS sequencer). I've 
been hunting for the MFC6070 audio amps which are used as tank drivers 
(reverb, not Army!).  No luck on any of these yet though.

I'm yet to try the KS parts of the AKS - so far I have only serviced the 
main body.

Interestingly, the traffolyte grid that covers the matrix can be removed 
without taking the matrix out. Doing so doesn't involve any disassembly of 
the matrix I am glad to say.  If you look at the pictures on 
www.richardcraven.plus.com/EMS/ you can see that the original silk-screened 
lines on the patch panel had worn off. It seems that some of the early EMS 
units (certainly some of the VCS3s) had the lines engraved rather than 
screened on.

Well, a friend at work (thanks Mark) has used a PCB router (AKA a scratcher, 
from LPKF http://tinyurl.com/ynge2g ) to engrave with huge success the 
original lines. I'll stick a picture up shortly - same URL as earlier.

The VCOs on unit 1 do indeed drift around but not so bad once they've warmed 
up. I've got some tempco resistors (thanks Senso) and some matched pairs to 
stick in once I get the rest of it sorted out.

Onwards and upwards

RMC, England