I just finished a restoration project on my OB-8. Replaced all electrolytic capacitors on voice boards and PSU, replaced all trim pots with sealed multi-turn pots, installed brand new keybed rubber contact strips, installed new CEM3340 rev G VCO’s (not really needed, but I figured why not). The single-turn trim pots are good enough for much of the calibration. The filters on the other the hand really benefit from multi-turn pots. Properly calibrated filters is key in getting the full sound that the OB-8 is capable of.
See, this is what I was aiming for a while back. I thought it would make sense to just recap the entire synth but I was told it was a bad idea... :-/. I then tried recapping just the power supply and did something wrong so it went in for service... but even after I was told it was fully calibrated, I still have a voice that just decides sometimes not to tune. I end up just disabling it from the start and deal with it but that's no way. Thanks so much for posting these. It really makes me want to go through and do all the voices and trimmers just to keep it going for many more years.
@ 21:30 Once you begin your VCF Volts Per Octave test, what device are you using that is telling you what the correct pitch should be. Are you running the OB8 audio output through an external strobe tuner?
Wouldn't it be better if the right end wood panel would be back in place before running the drift test ? Or it doesn't make any difference ? Thanks for these interesting videos.
I have an OB8 with A7 (which the service manual says has the 'good' envelope calibration. Any chance of a quick walk though video of that? I want to make sure I'm doing it right. You videos have been indispensable in my rebuild thank you SO much.
Not drastically and only for the better. If there is a change in the sound it's restoring it more to what it was when it left the factory. There are a number of electrolytic capacitors in the signal path that are replaced in this process. Other components are to improve oscillator stability and precision of calibration, which IMO is an improvement. When I calibrated this one's filter, the voices were wildly inconsistent, so yes, calibrating the filter changed the sound of the synth, to bring uniformity between the voices. Nothing sucks more than getting 8 different sounds out of the same note.
The DAC has pretty good resolution. You can see with the single turn trimmers it's actually challenging to get both LEDs lit up solidly, so the self-calibration window is pretty narrow.
The OB polys, and especially the OB-8, seem like the most enjoyable synths to work on. Easy access to everything and just really well designed.
If there's any interest I can post the whole video where I go through and demo each of the OB-8 patches.
Synth Chaser that would be very nice
The sound of this synth is just...incredible.
Thanks for this video. I just calibrated my ob-8 and this video helped me tremendously. Cheers.
I just finished a restoration project on my OB-8. Replaced all electrolytic capacitors on voice boards and PSU, replaced all trim pots with sealed multi-turn pots, installed brand new keybed rubber contact strips, installed new CEM3340 rev G VCO’s (not really needed, but I figured why not). The single-turn trim pots are good enough for much of the calibration. The filters on the other the hand really benefit from multi-turn pots. Properly calibrated filters is key in getting the full sound that the OB-8 is capable of.
See, this is what I was aiming for a while back. I thought it would make sense to just recap the entire synth but I was told it was a bad idea... :-/. I then tried recapping just the power supply and did something wrong so it went in for service... but even after I was told it was fully calibrated, I still have a voice that just decides sometimes not to tune. I end up just disabling it from the start and deal with it but that's no way. Thanks so much for posting these. It really makes me want to go through and do all the voices and trimmers just to keep it going for many more years.
Great channel! Keep up the good work.. Very usefull!
@ 21:30 Once you begin your VCF Volts Per Octave test, what device are you using that is telling you what the correct pitch should be. Are you running the OB8 audio output through an external strobe tuner?
Exactly, an external strobe tuner. You could also do it by ear.
You’re the best! Thanks so much!
Wouldn't it be better if the right end wood panel would be back in place before running the drift test ? Or it doesn't make any difference ? Thanks for these interesting videos.
I don't think it matters. There's not normally a temperature build up inside the case of these that would affect anything.
I have an OB8 with A7 (which the service manual says has the 'good' envelope calibration. Any chance of a quick walk though video of that? I want to make sure I'm doing it right. You videos have been indispensable in my rebuild thank you SO much.
I don't have an OB-8 here now. Maybe next time I get one.
But my question is: is the OB8 sound affected by the rebuild of the boards?
Not drastically and only for the better. If there is a change in the sound it's restoring it more to what it was when it left the factory. There are a number of electrolytic capacitors in the signal path that are replaced in this process. Other components are to improve oscillator stability and precision of calibration, which IMO is an improvement. When I calibrated this one's filter, the voices were wildly inconsistent, so yes, calibrating the filter changed the sound of the synth, to bring uniformity between the voices. Nothing sucks more than getting 8 different sounds out of the same note.
Synth Chaser ok thanks! But how can you get a lot of accuracy with only two LEDs ?
The DAC has pretty good resolution. You can see with the single turn trimmers it's actually challenging to get both LEDs lit up solidly, so the self-calibration window is pretty narrow.