E-MU ESI-2000 submix output question

Synth Repair
1

Hi all, the submix outs on my ESI2k are behaving strangely – they pass audio when voices are routed to them, but it is weak (very low volume) and lacks all bass as though highpass filtered. I know the submix outputs are TRS send-return jacks and I have tried 1/4" TS cables, TS cables inserted halfway, and TRS Y-cables checking both Tip and Ring ends, so I’m sure it’s not a cabling problem.

I’ve also tried “exercising” the jacks in case corrosion is the culprit – but in that case I would expect either no sound or intermittent/noisy sound. This makes me think it is the internal jack detection switching circuitry (Diagnostic menu - submix jack detect always reads “Y” no matter if a cable is plugged in or not). Anyone seen a problem like this before, on ESI or any other E-MU?

I haven’t been able to find ESI2K schematics but the EMAXII schematics I dug up showed it using a 74HCT244 buffer/line driver IC in the submix jack circuitry; I notice this is a part for sale on Syntaur’s ESI-2K page. Could replacing this IC have any effect on the submix audio outs? Machine is 25 years old at this point…

Any help or suggestions would be greatly appreciated!

2

before you do this check for solder breaks on the jack connectors. mechanical stress could have caused a break.

3

Good point, I’ll check the solder joints tonight. Although the problem is the same on both jacks… I’ll probe around behind the jacks and see if I can find where the audio goes bad.

4

use a continuity meter.
next you need to check rails on op amps.
but one step at a time.