Ensoniq esq-1 dead notes/velocity

Dave · Post by **Dave** » Tue Jun 07, 2022 4:03 am

Hi! My Ensoniq esq-1 has dead notes every 7 or 8 notes and now has zero velocity. Every note plays at its loudest velocity no matter what. I thought it was a voicing chip but when I use another synth via midi to play the esq-1 every note plays fine with normal velocity. Anyone know the issue here?

Post by **Ashe37** » Tue Jun 07, 2022 10:57 am

Sorry i can't be very specific buy i remember this being due to something with the scanning chip on the keyboard.

meener777 · Post by **meener777** » Thu Jun 09, 2022 4:51 am

Often if there are dead keys and its every 8 or so keys that is one of the lines on the keyboard matrix is not working properly. The schematics for ESQ-1 can be found here. Scroll down to the bottom and look for the "hand drawn" schematics.

http://www.buchty.net/ensoniq/

This one looks relevant but definitely not *super* useful: http://www.buchty.net/ensoniq/files/esq1-tg/20.jpg

Here is a messy copy of same part of the circuit from the scanned schemtics:
http://www.buchty.net/ensoniq/files/sch ... digit1.gif

It looks like kbd connects to the 6500 processor and that sends out serial to the DUART. If most keys are getting there fine and only every 7/8 are not that sounds suspiciously like one data line coming in is bad and the downstream stuff is okay. I would look upstream of the 6500.

You do want to be really careful, there are some nearly irreplaceable 6500 series processors with ROM inside the package that cannot be read out. Buchty has built a replacement for the one on the display board, I am not sure if the keyboard has one of these early microcontrollers as well but it looks like it is one to me since it has only bus connections in/out and no rom connection. If so be super careful not to apply power out of spec to that chip. In fact yes according to the scanned schematic I believe it says 6500/11 which is the same type of microcontroller. Dont blow this chip at all costs.

Looks like there are three sets of 8 lines coming into the 6500/11 controller. Not sure how this works but it could be that one of these is "row" and another is "column" in the keyboard matrix, giving 64 possible values to map the 61 keys. The other set of 8 could be an 8 bit encoded aftertouch value. This is all totally a guess. But if thats all correct it could just be something on the keybed itself is busted and data is longer getting to the 6500/11 properly. A crack or cold solder could be getting worse. I would look there first, carefully visually inspect any circuitry on the keyboard itself and see if there is anything obvious. If you are lucky enough to have access you might try a keyboard from another unit.

Also you can sign up for buchtys mailing list and see if someone there can help, he is definitely an expert on this synth.

[edited to clean up a few typos]

meener777 · Post by **meener777** » Thu Jun 09, 2022 5:12 am

I dont have time to take mine apart to check for sure but here is a picture of the keybed board (and it is for sale)
https://www.keyboardkountry.com/ensoniq ... stic-case/

looks to me like approximately 24 pins coming off it which would be about right for the inputs to that 6500/11 controller on the main board. my guess is something is going wrong on this piece. This all jives with Ashe37's initial advice, which also sounds like something on the keyboard. I cannot seem to find the schematic for that part of the synth though so far.

Ensoniq esq-1 dead notes/velocity

Re: Ensoniq esq-1 dead notes/velocity

Re: Ensoniq esq-1 dead notes/velocity

Re: Ensoniq esq-1 dead notes/velocity