Vintage Synth Repair

hi all,

i was wondering if anyone has any suggestions about diagnosing/fixing a
power supply problem on an arp omni mk1...

i had the instrument plugged in and was wiggling one of the keyboard
connectors on the lower voicing board when a plume of smoke wafted from
one of the 4.7 ohm resistors on the power supply...i disconnected power,
replaced the toasted resistor, along with the tantalum caps (2 10uF and a
1uF) on the theory that whatever smoked the resistor probably took the
caps along with it...this same scenario occurred once before and the above
fix solved the problem, but this time, i am only getting output of +2/-2 V
from the power supply when i should be getting +15/-15...

any suggestions would be greatly appreciated

thanks, PB>>

-- 
Peter Brown                 Senior Software Engineer
Dept. of Computer Science        140 Governors Drive
University of Massachusetts   Amherst, MA 01003-4610
Phone: (413) 577-2505            Fax: (413) 545-1249
pbrown@...  http://www.cs.umass.edu/~pbrown

--- Peter Brown <pbrown@...> wrote:
> hi all,
> 
> i was wondering if anyone has any suggestions about
> diagnosing/fixing a
> power supply problem on an arp omni mk1...
> 
> i had the instrument plugged in and was wiggling one
> of the keyboard
> connectors on the lower voicing board when a plume
> of smoke wafted from
> one of the 4.7 ohm resistors on the power supply...i
> disconnected power,
> replaced the toasted resistor, along with the
> tantalum caps (2 10uF and a
> 1uF) on the theory that whatever smoked the resistor
> probably took the
> caps along with it...this same scenario occurred
> once before and the above
> fix solved the problem, but this time, i am only
> getting output of +2/-2 V
> from the power supply when i should be getting
> +15/-15...
> 
> any suggestions would be greatly appreciated

Here's a link to a thread somebody saved from the
Analogue Heaven mailing list with regard to some of
the most common Omni problems, including what I think
may be bedevelling you:  the power supply decoupling
caps that are found in abundance on EVERY board. 
Check it out!

http://members.bluefrognet.net/~rlsnuffy/omni2/omni_repair.txt

BaM

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