Vintage Synth Repair

I have recently aquired an ob-8. Upon firing the bad boy up i found
the sounds to be wierd and pots to not seem to work correctly. SO i
downloaded the service manual and started folloing the calibration
steps.
power supply calibration went great got those Exact!!!
DAC calibration had a bit of an issue. DAC Offset went ok, but i
noticed a steady but slow voltage drop.. calibrated to 0.000v at the
closest avg time i could.
DAC SCALE went a bit rougher with the pot all the way counter-
clockwise I am only able to get to 9.85v instead of 10.00v ot say to
tune it to 10.00 +- 5mv

bend trimmers went excellent....

adjusting envelope offsets i didnt do they seemed steady (assuming i
understood the instructions correctly

Oscillator volts per octave went very very bad....
while checking osc1 all 8 voices light led3 but do not adjust to the
point that 2and3 light. osc2 the lower board sometimes led3 blinks
rapidly and sometimes it will stay on steady... the upper board led3
blinks constantly thru all voices.....this prevents corectly being
able to adjust the filter envelope modulation into osc2
seems weird that both oscilators for each voice would all be bad.....

led test went fine

switch test hold and programmer 1 and 2 tend to blink slightly when
pressed... probably corrosion (think i can fix that)

Pot test went bad as well... all pots seem to be erratic when using
the led test to check the pots....

oscillator drift test.... i get lights on under keyboard double and
upper light and under group b and d light seeming to mean that voice1
osc2, voice2 osc2 voice3 osc2 and voice 4 osc2 are all bad... I am
running the test several times to see if this is erratic as well.....

Now these were done using the service manual but not using eco 427
since it refers to revision a7 and I have b5 did I do something wrong
there?

I am now lost in where to go next.... how to clean pots? or do they
have to be replaced? what can be making All oscilators run weird?

PLEASE PLEASE HELP!!!






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--- In vintagesynthrepair@y..., "Rich Nolden" <ready69@h...> wrote:
> 
> I have recently aquired an ob-8. Upon firing the bad boy up i found
> the sounds to be wierd and pots to not seem to work correctly. SO i
> downloaded the service manual and started folloing the calibration
> steps.
> power supply calibration went great got those Exact!!!
> DAC calibration had a bit of an issue. DAC Offset went ok, but i
> noticed a steady but slow voltage drop.. calibrated to 0.000v at the
> closest avg time i could.
> DAC SCALE went a bit rougher with the pot all the way counter-
> clockwise I am only able to get to 9.85v instead of 10.00v ot say to
> tune it to 10.00 +- 5mv
> 
> bend trimmers went excellent....
> 
> adjusting envelope offsets i didnt do they seemed steady (assuming i
> understood the instructions correctly
> 
> Oscillator volts per octave went very very bad....
> while checking osc1 all 8 voices light led3 but do not adjust to the
> point that 2and3 light. osc2 the lower board sometimes led3 blinks
> rapidly and sometimes it will stay on steady... the upper board led3
> blinks constantly thru all voices.....this prevents corectly being
> able to adjust the filter envelope modulation into osc2
> seems weird that both oscilators for each voice would all be 
bad.....
> 
> led test went fine
> 
> switch test hold and programmer 1 and 2 tend to blink slightly when
> pressed... probably corrosion (think i can fix that)
> 
> Pot test went bad as well... all pots seem to be erratic when using
> the led test to check the pots....
> 
> oscillator drift test.... i get lights on under keyboard double and
> upper light and under group b and d light seeming to mean that 
voice1
> osc2, voice2 osc2 voice3 osc2 and voice 4 osc2 are all bad... I am
> running the test several times to see if this is erratic as 
well.....
> 
> Now these were done using the service manual but not using eco 427
> since it refers to revision a7 and I have b5 did I do something 
wrong
> there?
> 
> I am now lost in where to go next.... how to clean pots? or do they
> have to be replaced? what can be making All oscilators run weird?
> 
> PLEASE PLEASE HELP!!!
> 
> Upon checking the oscilator drift test each time a different set of 
oscillators report bad.... leads me to believe something else might 
be wrong.....

> 
> 
> 
> 
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