I have a v3.00.00a 20MHz GSP-2101 that sounds pristine and gorgeous for a few seconds and then sputters and dies,

Have seen the April 2000 schematic, but the doc doesnít appear to contain a block diagram which would est where breakdown is occurring. I wasnít previously aware of such sophisticated analog signal facilities in the 2101.

The tubes and the analog section seem to be fine. The bar graph meter seems to work correctly. Clean bypass signal always works. Compressor, FX69 circuit, tube distortion, analog EQ all work fine. The mono FX send always works and carries the correct, clean signal. While the programmable noise gate does behave normally when settings are changed (as observed from the mono FX send) I still canít be certain that downstream (toward ADC) is 100%.

So there is no response ever from the the rear stereo FX return inputs, regardless of settings.

I canít put in a mono/stereo line level source through the digital FX (back half) of my 2101.

If the unit is on in a 68 degree room for 30 minutes and random presets are jogged through, at times the guitar signal will crackle through to the ADC and it will sound beautiful, for a moment. The XLR and the ľĒ outputs sound identical.

When it does work there is usually a harsh hum that cuts into the guitar sound, which then degrades to the minute natural hiss noise from the stereo DAC can be heard (when turned way up on the mixing board). Before this happens though, whenever I touch a guitar string or play a note it sounds like something is grounded-out, like the hum from touching the tip of an active guitar lead. The red Overflow indicator lights each time a note is played from the guitar or if the string is even touched.

Strangest of all is when my electric heat pump kicks on it will briefly restore the unit back to normal operation, perhaps a few minutes. What is happening when this sag occurs? This is why I suspect component failure rather than bad connection. Something is wrong where the analog audio output meets the digital input converter. This could have something to do with the Silencer(TM) digital noise gate/detector.

Without a block diagram I canít figure out where between the two halves to look. Any thoughts? Should I pull the board out and resolder? Any help seriously appreciated, it was my 90s dream to have this processor making dreamy sounds, drenched in flange.