[sdiy] Prophet 5 question

[Barry Klein]

Wow, I guess all P5's I worked on were 2.2's or just my memory retention is
flawed - I don't remember that strip.  No, I would not remove it.

1. remove all socketed IC's that take 15V (maybe one of em is the culprit)
2. get an ohm meter that is good at reading low resistances - maybe an ESR
meter for caps...?  See if you can find the short by finding the lowest
resistance path.
3. Get a lab supply with current limit capability function.  Short its
output and set current limit to 2A.  Connect to +15V input and increase
voltage from zero until you get the 2A or so.  Feel for warm traces or
parts.  Or go exotic and take a picture of it with IR film(!).

Barry




-----Original Message-----
From: Karl Ekdahl [mailto:elektrodwarf at yahoo.se] 
Sent: Wednesday, April 01, 2009 11:42 AM
To: Barry Klein; synth-diy at dropmix.xs4all.nl
Subject: RE: [sdiy] Prophet 5 question


> have a photo?

http://www.sdiy.org/knas/temp/IMG_3828.jpg

> sure you didn't put a cap in backwards.... :-)

Yeah...  it didn't work once powered on and it's apparently been sitting in
a closet for 10 years so after noticing it not working i immediately found
that the PSU was being shorted by this PCB so i replaced the caps... no
backwards caps.

Karl


> 
> 
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl
> [mailto:synth-diy-bounces at dropmix.xs4all.nl]
> On Behalf Of Karl Ekdahl
> Sent: Wednesday, April 01, 2009 11:01 AM
> To: synth-diy at dropmix.xs4all.nl
> Subject: [sdiy] Prophet 5 question
> 
> 
> Hi list, working on a faulty Prophet 5 which has a short on
> the +15V supply
> somewhere on the CPU board - i notice that there's some
> kind of white
> power-rail distribution tab that runs about 2/3 of the
> upper PCBs, question;
> is it a bad idea to desolder this entire thing? It seems
> like it'd be so
> much easier to find the faulty parts if the different parts
> were separated
> this way. And yes, i have replaced all Tantalum caps on the
> board and
> reseated all ICs.
> 
> Karl
> 
> 
>      
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