[sdiy] Arp Odyssey 2 dead PSU

[Antonio Tuzzi]

Solved!
(and more...)

was a transformer failure of a special kind...

I tested the diode bridge as suggested by Micheal,
But everything was fine
and ok were also the 2n3904 and 2n3906
and so the power transistors...
(and the tantalum caps)
(I was going to change the ua723...)

inspecting the board fror the foil side i discovered the GND track
from the the main GND to the Rail GND was interrupted, seemed like
FUSED!
(maybe a power surge when the synth unattended ? Don't know!!! How can
happen something like that)

anyway, recreated the connection and the PSU was ok again, -15v GND +15V

but when connected to the boards, the -15v was dropping to GND

attaching one board at time, the responsible was the board A (the one
with CV memory and portamento and transpose). The tantalum cap C1
(1uf) was dead.
substituted it and this was luckily last damage! (pffffffeeeewww, I
was worried the for very delicate 4023 that is a pain to desolder, and
or the VCOs)

invested some time changing a couple of slider too... an trimmed it completely

what a wonderful synth!! ;)

thank you for your support!!

antonio





On Sun, Nov 29, 2009 at 4:44 PM, John Mahoney <jmahoney at gate.net> wrote:
> Transformer failure?
>
> John
>
>
> At 05:45 AM 11/29/2009, Antonio Tuzzi wrote:
>>
>> Dear SDIYers,
>>
>> suddenly my ARP ODYSSEY is dead...
>> tested the PSU and is giving
>> -60 V on the -15 V rail
>> and 0V on the +15V rail
>>
>> OUCH!!!
>>
>> questions:
>> I really don't understand how this could happen...
>> anyway
>> the 2 tantalum on the PSU board are ok
>>
>> 1) do you think that something wrong happened to the boards A B and C
>> powered at -60 and 0 ?
>>
>> 2) Can I consider directly responsible the UA723 regulator ? (I hate
>> the ARP PSU design!)
>>
>>
>> thanks
>>
>> Antonio
>
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