ESQ 1 Half a display

Hi everyone,
I recovered an ESQ1 which has been stored in an unheated shed for about 20 years.
Although it looked in great shape, when I tested it, it started up but with only half a screen and a few select buttons that do not work anymore.

It played fine with good sound quality, but when I wanted to change the MIDI channel it went a bit haywire…
And now it does not play anymore…

I opened the synth up and cleaned the electronics thoroughly with a correct cleaning agent, disconnected and reconnected all the connectors, but it did not provide an improvement. NO change, still only half of the screen.
Can you tell me what I should try next ?

Thank you for your time.

Best regards,


Regarding the display:
The schematics can be found at Rainer Buchty’s site:
The display part is this:

might be a broken pcb trace for the TL5812 or a dead TL5812

What “correct cleaning agent” did you use?

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Hi, Thx for the info.
I have already contacted Rainer, but got no reply. Does he still sell these spare parts ?

The cleaner I used I got from the electronics guys at the company where I work. I showed them the pics and they gave me a spraycan with a brush for cleaning electronics boards. Afterusing it, the white marks were all gone and the board looked brandnew.
Best regards,


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I have a SQ-80 which is the same display as the esq1. I would try reflowing the solder on all of the connections to it. That made my intermittent display work as good as new. Might be good to check that all of the IC chips are well seated.

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Rainer works as professor at the university and the term didn’t start yet. So maybe he is on vacation