Hi all -

I’ve got a Polaris on the bench with some issues. It came in with a dying membrane, so the first order of business was to replace that. Done and working.

Once I was able to control the machine again, I discovered that all 6 voices fail autotune.

I hit Tune All and the computer disables all 6. LED doesn’t even blink - just lights once and goes out.
When I manually re-enable the voices, both oscillators on all 6 voices work and track the keyboard. They’re just out of tune and out of scale.
Checked the calibrations on the PSU, DAC, ADC according to the service manual, all are perfect to 4 decimal places.
Checked the DAC by sweeping filter and detune, and all bits seem to be working (no glitches).
Watching the Tune buffer on the output board on my scope, when I hit Tune all I see 6 waveforms flash by, then nothing.
The output of Z62, the 4051 mux'ing the tuning standard voltages to the DAC, looks right (at least, I can make out different voltages in the pulse train, and they’re all around 2.5-3V)
The output of Z31, Channel Control for the Aux switches, looks right (IOW, as I hit Tune All and probe each output, I can see each one go high for a moment)

Thinking that perhaps the v.7 EPROMS in there had begun failing, I burned fresh v.11 ones and installed them. No change.
Everything in the machine seems to be behaving fine (as best I can tell at this point) except auto-tune.

Dunno if this is relevant, but the headphone output seems a bit noisy - it’s a high-piched digital-sounding sort of thing. It’s low enough that it would probably disappear in a mix, but it’s pretty obvious straight out of the back of the unit.

Thoughts?

Thanks,
Eric