ESQ-1 Buttons not Responding

I bought a very clean ESQ-1(plastic) but non of the buttons is responding. The display, keybed and audio are ok. Any hints on what might cause this ?

Note:i found the main fuse and one one the PS were blown(closest to the keybed)

I don’t have an ESQ-1 so here’s just some general advice: In general, buttons that barely (or not at all) respond to presses are a common problem with old equipment. However, luckily that also means that it’s an easy fix as replacement buttons are easy to source (e.g. directly from Syntaur). You can use a multimeter in continuity mode to verify that the buttons are working - place the probes on the contacts that are on the opposite sides of the button. When pressing the button, there should be continuity. If there isn’t, the button needs to be replaced. Unfortunately if that is not the case, the problem lies deeper. :\

Thanks for the reply. The buttons themselves are working so it must me something else common to them.

There is a cable between the top two boards which i’ve also reseated but no luck either.

if you can work on electronics, open it up and inspect for tampering by previous owners. chances are something is unplugged. but why is it unplugged that would be the question. if its been tampered with, return it to the seller for a refund and look for another keyboard.

If everything is ok inside, look for a failed solder connection on the wiring to the board in question. use a multi meter to confirm the wires are making a good connection.

if you replaced the fuse and trouble shooted the connection, and it still blows then you have a shorted capacitor or transistor on that board. Inspect every part and replace what’s bad.

Tantalum capacitors a the bane of synths. as they are timing out at this stage, all tantalum caps should be replaced even if they look fine. test them regardless. if you find one that is burnt, replace it and the synth comes back to life, then you may get away with that, until the next one fails.

So the fuses didn’t blow blow again after replacing them. I performed hard reset and now i can hear piano like sound. It plays normally.No loose connectors or blown caps. The screen shows the normal startup message with rom version and regular stuff.

I suspect something is wrong on the serial com between the display and main board. It might be a simple continuity issue or perhaps the buffer chip.

Since the displays works i believe the serial come from main to display board is good and so are the main chips.

Next step is to check for bad soldering points and the buffer chip function.

If you need an ESQ 1, I have one that everything works except for the Eb key that I will sell for $300.00

In what way are they working? Have you put a meter on them and determined that they are all reliably changing state with uniform pressure? Every piece of gear I own from the 80s has required new tactile switches. One Korg from 92 just got them also. The only type that might last longer are ones hidden away under a plastic membrane but the ESQ ones are not.

Also note that software was pretty kludgy back then. Illegal key combinations often just fail silently so make sure that what you’re trying to do it a valid action before determining it’s the button.

I’ve checked them with the MM.They are working properly. I can see they are doing something when pressed because the screen makes a slight/faint flicker.

caps are allways the culprit, sometimes a bad cap can also blow voltage regs or diodes as well.

Ensoniq also has always used high resistant conectors which means if you pull them by the cable and not the conector then you will have a dead cable. I managed to do that to my asr-10 rack and had to replace every ribbon cable in the unit to gt it back working.

Also ensoniq’s are known for there very hot power supplies which doesn’t do the water based caps any good. so replacing all the caps in the power supply board is a must at that age of equipment.

Do some of the buttons not respond or all of them ? If they work with the MM check the connections to the logic/microcontoller on the display. The display microcontroller reads all the buttons and sends them to the mainboard. It’s possible that it’s also maybe partially faulty but there’s replacements and lots of parts ESQ1’s out there. The fact that it plays from the keyboard tells me it’s not the keyboard microcontroller which is almost impossible to find