Vintage Synth Repair

II still distrust the power supply, so retest it at multiple points and walk
your way down it towards the CPU and look for shorted connections, something
going to ground etc.  Also test from the other end at the power inputs for
the cpu and work back from there.  Look for the caps to ground as well.

Is it possible to reverse the -15 and +15 connections?  Its been a while
since I opened mine.  Lorne

 

 

From: vintagesynthrepair@yahoogroups.com
[mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of Lorne Hammond
Sent: October-27-13 11:09 PM
To: vintagesynthrepair@yahoogroups.com
Subject: RE: [vintagesynthrepair] Strange TR-808 reset problem

 

  

Did you recap the power supply? One the 909 it is possible to overheat a
thin trace hidden under one of teh big caps.  Also I put in new transitors
and acps and one of them was actually bad.

I raelly suspect your power supply.  Lorne 

 

From: vintagesynthrepair@yahoogroups.com
[mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of cxacxu
Sent: October-27-13 9:08 PM
To: vintagesynthrepair@yahoogroups.com
Subject: [vintagesynthrepair] Strange TR-808 reset problem

 

  

Got a strange problem with an 808 here, the CPU will only start up when the
+15v rail is disconnected. When +15v is connected the CPU does not start and
the first light of step 1 does not light, the 5V and +/-15V rails are all
steady, When the +15V is disconnected the cpu will start up and the
sequencer will run. Any thoughts?

 

L