Korg PS 3100 ...need help

ultima · Joined: Dec 20, 2006 Posts: 3 Location: Iceland

I realise this is Synth DYI but im fixing the synth myself so i guess that qualifies, also im sure there are some knowledgable people around here and Im looking for help if anyone would be so kind?

The problem with the synth is that when Release is set to damped the A below middle C seems to sound different then other notes as it seems to react differently to decay settings on the envelope generator.

And when Release is set to Half damped or Release that same note acts as its stuck i.e doesnt stop sounding until i switch back to damped mode. Maybe its always stuck and i just cant hear it when the release is set to damped?

I also have three dead notes in the top octave but one thing at a time ... Smile

I have checked the the keys themselves and they are fine, no problem there.

The synth has 48 notes polyphony created by 24 signal generators and frequency dividers contained on two cards.

There are 4 Gate cards and three control cards that supply the filters, envelopes, lfo 's etc...

Apparently the edge connectors start cracking up due to age so i started by checking that and they were indeed cracked , I fixed up and cleaned all the edge connectors and made sure that they all work as they should, but still have the same problems.

Im now 99% sure its not the connectors.

Im going a bit nuts here so if anyone has suggestions on where to look for the fault ?

Would you suspect the Gate unit or the Signal generator ? I dont find it likely that the fault is in the Control units but im not sure.

really hoping that someone can help me out , I live in iceland and there's no keyboard techs around so i have no choice but to try and fix it myself.

Thanks
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update.

I swapped the gate cards around and the fault follows the gate cards.
I take it that the fault is in the gate cards , but what could it be on the actual card ?

blue hell · Posted: Mon Jun 18, 2007 5:58 pm Post subject:

Sorry to not be able to help you. I did a bit of a search for schematics, but couldn't find anything except for some filter stuff. Just wanted to say welcome, and hope you will succeed in solving the problem.

Eric G · Joined: Mar 07, 2007 Posts: 19 Location: Sweden

Hi!

You should definitely search the corresponding gate board for a bad soldering or short. Both the envelope generator and the VCA for each note is on the gate boards.

ultima · Joined: Dec 20, 2006 Posts: 3 Location: Iceland

Update :

The hanging note was cured by replacing the Mc14007 IC.
after replacing all transitors and caps for the hanging note in question and nothing changed i decided to replace the IC.
So if you have this particular problem , start with the IC!

That leaves me with 3 dead notes on gate board 4 and the LFO leak.

I tried replacing the Mc14007 Ic as well as the 324 Opamp for the dead notes and no luck there. Not sure what to try next except for changing all transistors and caps for those voices as well .

It seems unlikely that three consecutive notes would die as a result of bad caps/trans so im looking into whether the Signal generators are supplying sound to the gates for those notes. Make sense??

I cannot seem to find any bad solders or connections on the gate card 4.

As for the LFO leak , havent looked into that yet (im fixing in order of importance) but I have been told it might be the IC there as well.

Another problem i have found on gate card 4 is that one note has different decay behaviour , changed the MC14007 Ic and the Opamp for that note and no change , next its the caps and trans.