Chroma PS Question

[Dave Halliday]

Maybe a bad tantalum cap?

They fail shorted and the resistance of the PC Board traces might be high
enough so the power supply just gets loaded down by that much.  Maybe feel
the traces to see if they are warm - the warm ones will get cold after a
while and that spot marks your problems...  I would try measuring the
current drawn on each line first though.


-----Original Message-----
From: |||| Philip |||| [mailto:thelab at sprint.ca]
Sent: Wednesday, June 07, 2000 4:14 PM
To: synth-diy at node12b53.a2000.nl
Subject: Chroma PS Question


I got a DOA Chroma on a bad trade :( The unit was sitting at a friend's for
3 years. I finally got to see it last week. We checked the synth and the
problem seems to be with the power Supply. With no load (boards
disconnected) it pumps the appropriate +12 -12 +5 -5 and +24 but with the
boards connected, the ps's +12 and -12 outputs drop to about +5 and -5v. The
circuit board that causes this does not seem to be sinking that much
current. The problem seems to be that the ps is not regulating. Does anyone
have experience with this ps?  There is only one common component shared by
the +12 and -12v sections, an LM-358 op amp.

Thanks Philip