[sdiy] Prophet 5 question

[Bob Weigel]

klosmon wrote:

> Karl Ekdahl wrote:
>
>> 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
>>
>>
>>       ___________________________________________________
>>   
>
> Hello-
> It wouldn't be a bad idea (so long as you have a decent desoldering 
> technique);  it just might not help isolate the faulty component, once 
> you've removed it.
> The way I usually track such problems down is cutting the major +15 
> traces to the different sections of the board to narrow down where the 
> fault lies.
> On prophet 5 boards, I've found shorts caused by faulty .1 bypass 
> caps, faulty opamps and CMOS, and of course the aforementioned 
> tantalum caps.
>
> Good luck.
>
> ~GMM
>
I use a miliohmmeter.  If you have an esr meter it *might* work..but I 
have an hp that goes down to .001ohm sensetivity.  That way I can sniff 
out the short in a situation like this and get it at least down to a 
general vicinity.  If you don't have that handy then Greg's way is next 
best for sure.  Traces are easy enough to cut and resplice. -Bob