[sdiy] wonky JX3p

John Henson synthnerd at eircom.net
Mon Oct 18 16:55:06 CEST 2010

Hi there,
I have seen these symptoms before, first time several years ago on a JX3P
and more recently on a Jupiter 8.
Obviously check the power rails and CPU clock first to make sure the CPU is
getting its basic needs, then check the backup battery. If it is completely
dead, then I would suspect the 40H000 Toshiba chip that handles the battery
switching. When this is faulty the synth behaves as if the CPU is dead.
A 74HC00 is a good substitute IC.

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of
legion at helpwantedproductions.com
Sent: 17 October 2010 19:41
To: AH; Synth DIY
Subject: [sdiy] wonky JX3p

A friend of mine asked me to look at his JX3p. Initially it supposedly
only needed some keys cleaned but by the time he got it here it clearly
had some other issues.

When I turn it on all the lights but the LFO turn on and stay red. I
checked fuses and reset the cables so far but haven't gotten into anything

Has anyone seen this symptom before? Any suggestions on what could be
going wrong or things to look at to try and fix it?

I did some poking around and apparently there is no hard reset on a JX3p.
There is mention of a few different ROM versions but on opening it up I
didn't see anything that popped out as a specific OS ROM.

Any/all help appreciated.



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