ESQ-1 Intermittent key operation

Hello everyone,
My ESQ -1 has some keys that will not always sound when depressed.
I have not removed the keyboard yet. I thought I would see what others have to say before I disassemble this machine. Anyone know the fix for this ?
Thank You

The mechanism for sounding a note in the ESQ is pretty simple. The key up position stays against one contact and then you press the key it leaves that contact and hits a lower contact. The time it takes to go from one contact to the other determines velocity. My guess is that there is some oxidation built up on the little contacts. So simply cleaning them should get them back up and running.

This video will show you how to remove the keyboard. It’s pretty straight forward.

Hello Paul,
I cannot tell you how much I appreciate your response. I will look into this right away.
Thank You

Is it always the same key? Is it multiple keys? If the dropped sound is from random keys, that could be a problem in the clock circuit, which could the circuit itself or the power supply not feeding enough current and confusing the rest of the circuits. Power supply problems are usually solved by replacing all the capacitors with new ones. If the problem is the same keys, and it is happening to every 8th key, then that is a problem with the keyboard logic chip. Open the lid, locate every chip that is in an insert socket, and gently tap the top of the chip with a screwdriver handle or some such to reseat it. There might be some oxidation on the pins and the grips, and tapping may restore better metal to metal contact. I had the octave missing problem and tapping restored proper function immediately. So, it would be best to try reseating the chips, and then check the capacitors in the power supply for swelling. If you have a multimeter check the output voltage of the power supply. There is the ESQ-1 service manual availabe at If the caps in the ps have never been replaced, go ahead and order a couple of sets from some supplier like mouser and just replace them all. It can’t hurt and it only costs about $7 or $8 to replace all of them. Keyboard is practically brand new after that. If the problem key(s) are not every 8th key, then, yes, it could be keyboard contacts which can be cleaned with denatured alcohol (don’t spill it on anything else, use cotton swabs.) Keyboard problem is simpler than the others but more tedious because of all the repetition removing and installing the keys. Be gentle so the little bits on the keys do not break.

Hello Gridsleep,
It is not the same key all the time. Actually quite random as well as frustrating. lol
And I agree about the power supplies. I have this ESQ1 , two TS-10s and a pretty sick ASR10. If the ASR survives, I will be rebuilding all these power supplies…
Thank You for your expertise. It is much appreciated.

Sounds more like one of the voices is faulty. Try pressing the same key repeatedly. Given the synth has 8 voices press the same note 8 times, counting 1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8. If it’s the same voice not sounding each time then you know you have a dud voice.

The ESQ uses analog VCA and VCF. So if a voice doesn’t sound it’s highly likely to be a VCA.

Tested this out…It was fine… But thank you. I appreciate your interest.