oberheim ob-8 skipping voices

radek tymecki · Post by **radek tymecki** » Thu May 01, 2014 9:05 pm

my ob-8 started acting very weird. it started skipping voice 4 and 5. sometimes it plays ok, but most of the time this issue appears. what can it be?

synthparts · Post by **synthparts** » Sat May 03, 2014 12:40 am

When you do an auto-tune do those voices pass or fail (patch number buttons 4 and 5 blink)?

radek tymecki · Post by **radek tymecki** » Sat May 03, 2014 10:34 am

yes. button 4 and 5 are lit. sometimes 3, 4 and 5

synthparts · Post by **synthparts** » Sat May 03, 2014 10:30 pm

I meant after the quick scan 1 to 8 does it then come back and blink 4 and 5 several times to indicate a tuning problem?

synthroom · Post by **synthroom** » Sat May 03, 2014 11:05 pm

synthparts wrote:I meant after the quick scan 1 to 8 does it then come back and blink 4 and 5 several times to indicate a tuning problem?

Does the OB-8 disable voices that fail tuning?

synthparts · Post by **synthparts** » Sun May 04, 2014 2:00 am

Yes it should.

radek tymecki · Post by **radek tymecki** » Sun May 04, 2014 9:19 am

yes. those voices are later disabled. but sometimes they pass the test and are in tune

Claudio · Post by **Claudio** » Sun May 04, 2014 1:07 pm

radek tymecki wrote:sometimes they pass the test and are in tune

Hi Radek,

I used to have same issues with my Expander until I recapped the PSU (excessive ripple on power lines).

radek tymecki · Post by **radek tymecki** » Sun May 04, 2014 2:50 pm

i've recapped all electrolytics except 1uf because i had none on stock [they come 3 per voice]

synthparts · Post by **synthparts** » Sun May 04, 2014 10:06 pm

Have you done the tuning procedure on those voices lately? The OB-8 has the about the easiest tuning calibration of any analog synth. It just consists of turning the trimmers until 2 LEDs light up... See the service manual.

If those voices still fail try swapping the CEM3340s to other voices and see if the problem follows them. If you need any CEMs I have them in stock.

radek tymecki · Post by **radek tymecki** » Wed May 07, 2014 9:11 am

i've noticed that one pin of small tape from midi interface is broken. i've repaired it, also checked all connections from midi to cpu board. now after powering up it makes me sth like this. btw - when i disconnect voiceboard and keyboard it's still same

radek tymecki · Post by **radek tymecki** » Sat Jun 14, 2014 7:06 pm

anyone?

Jacob Hunt · Post by **Jacob Hunt** » Sun Jun 15, 2014 7:09 am

My OB-Xa did this because of a bad chip in the s&h circuit for the autotune circuit, I believe it was a tl084. I don't know how similar they are, but the circuit was on the bottom right of the bottom board for my later era OB-Xa.

TomV · Post by **TomV** » Sun Apr 10, 2022 12:33 pm

Hello,
I know, your question is old, but I had the same problem with the voices from 5 to 8 for a long time. My solution was very easy. After switching on my Ob8 I simply play some notes first and then press the autotune. The problem dissapears with my Ob.
tomV

oberheim ob-8 skipping voices

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