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Pics of the inside below.
"I just finished upgrading this flawless OB8. I am a retired Engineer who designed circuit card assemblies for Aerospace, but now have a labor of love restoring the synths I grew up loving so much in the 80’s. I only buy and repair vintage synths if they are in mint condition cosmetically and this one is probably the best I have ever found. I’ll list all of the upgrades made and will provide a video of Calibration for anyone with serious Interest.Many will claim that they are selling you a synth that has been serviced, but it’s never clear how long ago the service was completed or when the last calibration was performed. When you buy this OB8 I will complete a full calibration the day prior to shipping it to you.
This OB8 also comes with a nice hard case that will ensure you get your synth in one piece. It will be insured as well, of course.
Service date: February 15th, 2025
Replaced the following:
1) All Electrolytic Capacitors replaced on Power Supply Board, Voice Boards and Front Control Panels (Vishay Mfgr)
2) Bridge rectifiers with higher rating replacements
3) Lithium Battery replaced
4) All of these ICs replaced: CD4051BE, CD4053BE
5) All of these Op Amps replaced TL084CN
6) All trimmers on Power Supply and Voice Boards replaced with Bourns Multi-turn precision trim potentiometers (Model 3296 sealed trimpots).
7) Select resistors replaced with precision 15PPM versions
8) OBXa sound mod (Juergen mod). This adds more low end by eliminating the 22hz highpass in the signal path.
9) Replaced one connector terminal
10) Complete calibration procedure (Software version A3)
Power supply voltages calibrated to +15/-15V and +5/-5V respectively.
DAC voltages to 0 volts
Bend trimmers calibrated
Adjusted Envelop offsets > The microprocessor needed to be reprogrammed for these envelope offsets after I replaced the battery. Now dialed in perfectly and no problems to be rectified.
LED Test > Passed
Switch Test> Passed
Oscillator Drift Test > Passed
Filter Calibration > Passed and tuned perfectly with accurate voltage per octave
Output VCA Volume Adjustment > level on both boards
11) Reloaded Factory Patches and verified for accuracy
12) Tested full functionality of Factory Midi retrofit kit. Was also able to transfer sysex patches via midi, which many claim is not possible. It is in this midi kit."
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