I am having some problems with my ESQ-1


When my Filter “FREQ” parameter is high enough every eighth key I play will skip or just not play. Sometimes it will fizz in or bubble in or there will be a bump sound before or during the note plays or sometimes the eighth note won’t play at all. Turning down the Filter “FREQ” parameter usually gets rid of the problem but I don’t like knowing that there are some sounds I can’t get too. Any ideas on what might be causing this? I have done Filter tuning and everything checked out. (Values were between 146-153.) I have played eight keys with the filter “FREQ” turned down and all the voices seem to be function as in when I press down nine keys the first key cuts out as it should. I have done all the tests that I could from the outside of the synth, everything passed, and have not opened it up yet. Could this be a software problem? The software version is 3.40. I did do a factory reset and it did not help or atleast I don’t think it did. I will be updating that in the future and I do plan to open it up later today or tommorow. I do have a vintage synth repair place near to me and was wondering if any of you could point me toward the problem or even a possible solution. I have been asking around on forums and noone seems to know whats wrong… well actually noone seems to care as I have gotten no replies. The guy I bought it from does except thirty day returns but I would rather not go that route unless repairs seem too expensive. I really like this synth and really want to get it working! Any help would be greatly appreciated! Thank you. :slight_smile:

Here’s a video that demonstrates my problem that I took. https://www.youtube.com/watch?v=HgbGoGjwuSI


Probably a dodgy filter chip or part of the VCF control. There’s a section to the right of the PCB with 8 identical sections, those are the filter chips and associated parts. You might be lucky and they just need reseating.


What is the VCF control and if that is the problem (haven’t opened the ESQ-1 yet) where would it be located on the board?


I meant the digital to analogue control of the VCF. But given it only affects once voice it would seem to be more likely a fault on the VCF chip.

The ESQ-1 schematic scans on the web aren’t very clear unfortunately. The TL081 plays a part in the CV control anyway.


Thanks for your reply! This is actually my first synth and I m a beginner. I will learn a lot when opening this thing. I am a bit of a noob and still don’t understand the VCF filters but I will be checking out the SSM and the CEMs and if those are the problem then it should be a fairly easy fix. If those are not the problem then I will bring it to a local vintage repair place and have them take a look at it. Again. Thank you!


Given it has presets, the analog VCAs and VCFs are under digital control, so there’s a DAC to convert the digital number to a CV voltage level.