Ensoniq SQ-80 DOA

Hello all,
I’ve just recived a SQ80, well aware that it was not working. I took my chances and want to see if I can either repair it or sell it as parts.
Basically there is no sound from the unit and nothing on the display. I checked all power rails according to the service manual on Buchty’s site. https://www.deepsonic.ch/deep/docs_manuals/ensoniq_sq-80_technical_description.pdf
All good, but problem persist.
Also fuses are good.
Would be great to test with a known working display board, but I don’t have access to spare parts, so looking is I can do something else to find the issue.
No sound either, but there is a short rising sine tone on the output when powering off, so something is alive in there.
I have good technical knowledge, but again no access to spare parts unfortunately.

Maybe the best thing would be to see if I can find another broken SQ80 and see if I can get a complete one out of the 2…

I live in Denmark, and the market is not exactly overflowing with SQ-80’s and at the same time seems like many are geting their eyes opened for these old Ensoniqs. Increasing the demand and the price…

Any advise would be appreciated.


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On further investigation all power rails are OK both loaded and un-loaded. I start to wonder id it is the display, and if the main processor wait with putting on sound untill the display is on. I have detached the 4 pin signal cable which should put the display board in a debug mode and show characters based on inputs on the buttons, but still black screen. This must mean the display is broken. Is there a way to test to make sure?

Also it is strange that both the mainmaord and display board is fryed…

The display on my SQ80 was intermittent for a very long time then finally would not come back on. I reflowed all of the solder pins on the display board with great success. It’s been working very well for about 2 years now. Hope this helps

Thanks for the advice Klaw. I will give it a try. Does reflow mean removing the old solder material and adding new? or is there a guide to do it. I know how to solder, just not sure what you mean by reflowed :slight_smile:
@plauss was kind enough to look on his SQ80 and check if the main board is working without the display board connected, and this is not the case, so if I’m lucky only my display board has an issue.

Reflow = melt. There might be cold solder joints I remember having to add a little solder here and there. The pins coming from the display are very close together so be careful not to short something.

Here’s a discussion about it…

Let us know how it goes.