Hi everyone, I recently bought a broken ESQ-1 secondhand and have spent the past several days devouring as much info on troubleshooting as possible. Following the service manual, I took measurements of various power supply readings and wanted to make sure they are OK. I included some background info in a bolded subsection, but feel free to skip to the next section if you just want to see my voltage readings. Thanks!
To get up to speed, it arrived today, and I’ve powered it on and done a cursory visual inspection. As advertised, the ESQ-1 powers on but does not respond to any user input, nor makes any sound. Low internal battery voltage warning, OS V3.50. There are 2 VFD characters that seem to be stuck with all segments “on”. Here is a video of the VFD on power-up.
I tried the various Record + (key) combos to try reinitializing, analog input test, etc, to no avail.
Some other concerns/observations:
- The transformer says “1450000502” and PSU board says “4001006901 REV B”. Appears a ferrite choke has been added to the secondary leads. The service manual I’m using says the transformer should say “1450000301 115V”, but this isn’t the case. However, I see used transformers matching my P/N for sale on Syntaur, so I’m assuming this is fine.
- 5 screws securing the data entry/keypad board to the plastic case are missing. As a result, the bottom 5 soft keys press “into” the body of the synth, if that makes sense.
- Volume slider is snapped in half near the two solder lugs closest to the rear panel.
- Pitch wheel seems to rub against the enclosure when pulled toward the user (lowering pitch position)
- … most, if not all screws/bolts look pretty rusty. 1/4 jack nuts are rusty. Decent amount of dust inside. Possibly a severed insect appendage near a 12V regulator?
Okay, that’s the background info so far. On to the PSU readings:
Power supply readings
Referencing the terminal numbers from Figure 8 from pg. 26 of the Service Manual, here are the various voltages to check, their pos/neg terminal numbers, acceptable range, my measured value, and units:
Overall, it seems that the PSU is fine. I’ve highlighted measured values that were technically out-of-range. Nothing too crazy, but just thought I’d check: do these values seem reasonable? I took the “Analog GND” measurement a few times, and it seemed to range from -5mV to +1.7mV ish.
Okay, that’s all for now. I plan on replacing the lithium battery & recapping the power supply board with 105C, FC series Panasonic electrolytics as recommended by bradthx on YouTube (link to his ESQ-1 video). Any insights are much appreciated! Thank you!