Synth Repair: Ensoniq ESQ-1


I wish I did have access to one, I am pretty well a rookie when it comes to repair but trying to broaden my knowledge (kinda need to considering I’ve been making hardware based synth pop and techno for about 8 years haha)


I’m gonna open it up and check tomorrow


I agree, but I’ve seen counter evidence many times in old Ensoniq’s. I’ve had quite a few of them in my workshop over the last years. Three instances where an erratic (unstable) problem did not turn out to be PSU electrolytics:

  1. bad DAC (as mentioned earlier in this thread)
  2. bad resistor trimmer(!)
  3. bad filter IC


Hello. sorry to burge in…
I have a ESQ1 on my hands. cheap buy as usual. I have several issues.
First let me tell what i have resolved.

  1. It had low battery, replaced that all good.
  2. It had a faulty ribbon cable for the keyboard. and made the controller chip a bit hot. The ribbon was backwards and 2 wires interrupted. It works great now velocity and all.

All values are within range. the power supply all in range. the output opamp 084 +/-12v the -5v regulator on board ok. MJE-182 ok. 7 v out. but all filer values are 0 in filter calibration. will check again tonight power on all filters
2. The filter calibration results are all 0. all 4 envelopes work fine. (audio output is low)


Good morning, I got a lot of Good information out of this thread incl. the GSLTZ thread. My Esq1 arrived non working “no sound”

-Kybd ribbon cable was backwards
-Now I have sound but same as you
-Low output, no envelope, no filter

if I turn off and on again real quick I will get a high pitched squeal like the res and freq are at full blast but the sounds are open, still no envelope or filter control and they tune within range.

Did you find any more solutions since august? I am going to replace my TL081 and 74LS377 and AD7524 and hope its one of those, I was not getting any AC movement off those.

thanks for any information, sounds like we have / had the same issue.


Check 4051.
Check the voltages to the mux and from the mux. The AD should fairly hard.


I will, what were you typing about the AD?


Sorry, at work. the AD should fail pretty hard.
Check the 5v rail as well. check the input and output from the mux.


Hopefully between the AD7524, TL081, CD4051B and the 74LS377 I find the
issue as I have ordered replacements for all those in case. .

I will let you know, I sincerely appreciate your help on this!

Matt Luney


Update. A new 74ls377 and I now have filters back it seems. All tune quickly to about 60. However my envelope is still out. Notes sustain until end of sample and quick cutoff. Hopefully replacing the AD chip will solve this.


Never turn stuff off and on quickly!

You can damage RAM chips and other components. It takes a while for these old chips to discharge.