[sdiy] Jupiter 6 troubles

[John Henson]

Hi everyone,
I remember about 5 years ago having a JX3P in for repair which woke up brain
dead and with all the LED's on but very dim and flickery.
It had been knocked off it's keyboard stand several months earlier but had
worked fine until it died.
The transformer was hanging on by a thread, and there was hole in the floor
of the case where the mounting bolts had ripped through the chipboard, so I
thought the obvious, simple electrical problem caused by physical abuse.
I had a clock, power was fine, but the processor and all the support logic
were putting out gibberish. I started replacing the 373 latch, the address
decoding stuff with absolutely no difference, this one had an external
EPROM, so I suspected it, but not having a spare for that I cut out the 8031
and replaced it too. To no effect!
I checked the onboard battery obviously, but it was borderline, so I put a
lithium coincell holder in with a brand new battery to no effect.
Looked at the TC40H000 IC which deals with the battery and although I
couldn't see anything horribly wrong, I replaced it with a socketed 74HC00
and rebooted.
Lo and behold, perfect JX3P goodness.
There are several ironies here, how many IC's I had to replace to make it
work (13)
I have the full test equipment setup, but it didn't really help.
That was 5 years ago, and it's still fine, and the ultimate...
The CPU that I put in came from a dead central heating boiler controller.
A lot longer ago I had a dead JP8, with similar symptoms, it was just the 8
MHz crystal.
Regards
John
----- Original Message ----- 
From: "J.D. McEachin" <jdm at synthcom.com>
To: "Jeff Farr" <moogah at gmail.com>; "synthdiy" <synth-diy at dropmix.xs4all.nl>
Sent: Tuesday, July 03, 2007 12:10 AM
Subject: Re: [sdiy] Jupiter 6 troubles


> At 03:41 PM 7/1/2007 -0500, Jeff Farr wrote:
>
> >I've got a JP6 here for who the lights are on, but nobody seems to be
> >home.  All the buttons on the panel boards light up but don't respond
> >to being pressed.
>
> The LEDs are strobed by CPU.  If you can pull the CPU (some revs of the
controller board have socketed CPUs), you should see the LEDs turn off.
>
> Since all the LEDs are on, I'd say the CPU is executing bad data.  I'd try
reading the EPROM.  I can't say for sure, but Google should turn up a good
image to compare it to.
>
> Jeffrey
>
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