Tag Archive | Repair tip

Odyssey, CV at last!

\o/ \o/ Got the control voltage issue sorted out! \o/ \o/

Just to recap things from my earlier post, when triggering notes from the keyboard the CV output at pin 7 of opamp A1 was not driven higher than 4,5V. After swapping Q8 this was corrected (A1 pin 7 going to approx. 13V), but when measured from the junction of R26 and Q8 gate (keyboard CV out, interconnect pin 8) the voltage was still not driven past 5V. So, when playing the highest note on the keyboard (7V), there was a voltage drop of about 8 volts over R26.. Definitely some current leaking, but where?!

All this time, I had had the interconnection board removed/disconnected so there was no load on the CV out pin. Still, when measured against ground this junction showed a resistance of 1kOhms; a thing, that should’ve pointed me direction of what to check next. Unfortunately I just wasn’t thinking far enough at this point.

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Odyssey, board A

Finally on to the parts swap and electronics repairs with my precioussssssssss! On board A, the parts that got swapped were R36-R46, C3, C9, C10, C12-C15 and C18. I didn’t have any suitable replacement for C16 at hand so I just left it as-is. In case you never memorized the locations of these parts, why not take a look at p27 of this service manual.. ;)

Broken items on board A were the up2oct calibration trimmer T4 (measured 4Mohms instead of 250R), FET Q8 of the CV output FET-input opamp buffer (not driving CV out higher than 4,5V) and pink noise generator opamp A4 (no output). There was also a bad solder connection on R32 (2nd voice output buffer opamp feedback resistor), this caused the 2nd voice CV output to drift at random.

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