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juno2 : unwanted bent

Started by nochtanseenspecht, February 08, 2011, 08:56:26 PM

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nochtanseenspecht

 :-\ i used a too long screw when closing the case of my fresh alpha juno, and hit the motherboard :-[
it seemes the software generated enveloppes are affected.. sustain and release behave really strange now
i guess that's it :'( well good for droney noises and basses still..

so..  if you screw your gear, screw it carefull

Gordonjcp

Shouldn't be a big deal to fix, if you can get hold of the service manual.  See if you can find physical damage around whatever you hit.  You may have cut through a track.  Also check the control voltage demultiplexers, they're shitey 4051s if I recall correctly.
If at first you don't succeed, stick it through a fuzzbox.

nochtanseenspecht

yeah i cut two traces, and worse, shortcut them :'(
that i repaired allready
resetting didn't help. i'm afraid i messed up the OS; apart from the spoiled EG, there's also strange steps when i open the filter, not the usual stepping. also at certain sustain settings, notes are retriggered several times, or freeze.

i am very much afraid that i have to search for a new motherboard.. there goes my bargain  >:(


Circuitbenders

i'd go with Gordon. Its going to be some crappy logic chips playing up.
i am not paid to listen to this drivel, you are a terminal fool

Gordonjcp

It can't be *that* faulty, otherwise it would be stone dead.  CPU faults tend to be a bit all-or-nothing on gear as simple as this.
If at first you don't succeed, stick it through a fuzzbox.

nochtanseenspecht

well if you both think so, i guess there is still hope  :)
the reason i tought of a faulty cpu is the the strange display message after my mistake and one of the affected traces going to a huge cpu looking ic.
ok i open it up again and see what ic's are there
but first go to Lee Scratch Perry here in Amsterdam tonight :)at least if he shows up ;D
Thanks Gordon and Paul !!

nochtanseenspecht

okay, i followed the shorted traces, and they go to several ic's :

-ml 58 153j (can't find datasheet)
-M74LS273P - OCTAL POSITIVE EDGE-TRIGGERED D-TYPE FLIP FLOP WITH RESET
-P8032AH - 8 BIT CONTROL ORIENTED MICROCOMPUTER

would it be wise to just replace the m74ls273p ?
i have no idea how to measure wether it is good or bad  :-[

thanks, david

Gordonjcp

The ML58153 sounds a bit like some sort of custom chip.  Any chance of a photo of that part of the board?

IIRC the 8032 is a ROMless microcontroller, so somewhere near it will be a ROM or possibly EPROM (got a quartz window on top, covered by a sticker).  The 74LS273 is an octal latch.  Now, the way the 80C32 family work is that they have a single 16-bit bus, with the lower 8 bits multiplexed between the lower 8 bits of the address, and the 8-bit data lines.  So when you want to read or write, the upper address is put on those pins, the lower address is put on the AD0-7 pins *and then an octal latch is triiggered to hold it*, then the lines are turned back to data lines to actually *read* the data.

Hang on, is the ML58153 a 28-pin PDIP chip?  I bet that's the ROM.  Buggering up those lines certainly could cause interestingly unpredictable behaviour...
If at first you don't succeed, stick it through a fuzzbox.

nochtanseenspecht

thanks Gordon  :)

no, the ml58153j looks like a resistor array, it has 9 pins in line and sit very close to the 8032,
and indeed, on the other side of the 8032 there's an eeprom (nec d271280-2 )

now that i look closer, the 5 in the ml58153j might be an S...

the camera got lost in the mess, but if i find it back later on, i'll post some pics

i know it is little information, but do you think there is still hope?
can buy another motherboard for 85 euro (+the old board), maybe that's a better idea.. :-\