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Xpander intermittent boot failures, hangs, memory loss

Xpander intermittent boot failures, hangs, memory loss

2016-06-16 by skoteinos@...

Hi!


I have owned a US-made Xpander for 1-2 months now. It sounds fine (awesome instrument) but it has some intermittent issues that I am struggling to diagnose; I wonder if they sound familiar to anyone.


- boot failure (display does not come on, no sound)

- hangs (sometimes in the middle of a note, sound continues, envelopes stop)

- (patch / global) memory corruption (paired with boot failures; after some time the machine comes up with 'reset memory?' dialogue, memory is garbled afterwards)


These things happen on their own or in combination. The memory corruption happens after a number of boot failures usually. After a hang their sometimes are a couple of boot failures (and then if I'm lucky, memory corruption).


The machine got a full recap last year, and has a new transformer. The only original part in the power supply is the pair of varistors on the transistor that provides overvoltage protection.


All power readings check out (according to specs from the service manual) when measured with a digital multimeter. Battery voltage is OK both in powered up and powered down states.


Does anybody here have a clue where I should look for broken parts? The internal self-checks all pass.


Thanks in advance for any insights!


Cheers, Jacob


PS

I previously posted on Gearslutz: Oberheim Xpander power up / memory corruption issues

Oberheim Xpander power up / memory corruption issues
My Xpander has developed regular issues where a combination of some of the following things happen. Apart from these issues it works perfectly: all
View on www.gearslutz.com
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Re: [oberheim] Re: Xpander intermittent boot failures, hangs, memory loss

2016-06-18 by Bob Grieb

Could the CPU be getting a spurious reset pulse every now and then?
Also, maybe try programming some new firmware EPROMs, in case the old 
ones are starting to get "bit rot".   Not new code, just newly programmed 
EPROMs, as something to try.   I guess you could also try replacing the 
6809 itself.   There are two of them, so I guess either one could be causing 
your symptoms, right?

Bob


--------------------------------------------
On Sat, 6/18/16, skoteinos@... [oberheim] <oberheim@yahoogroups.com> wrote:

 Subject: [oberheim] Re: Xpander intermittent boot failures, hangs, memory loss
 To: oberheim@yahoogroups.com
 Date: Saturday, June 18, 2016, 7:01 AM
 
 
 
 
 
 
 
 
 
 
         
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 I replaced the old varistors today, no improvement.

Re: [oberheim] Re: Xpander intermittent boot failures, hangs, memory loss

2016-06-18 by skoteinos@...

Thanks for the ideas Bob!

Yes it looks like the Xpander uses 2 MHz 6809 processors ('68B09'). Mine has Hitachi's in them (HD68B09P); I ordered some new ones on Ebay just now. USD 30 including shipping to the Netherlands (but excluding import duties... will see).

I think I will manage popping IC's in and out of sockets but burning EPROM's would be a step up for me. I think I would rather buy a set of pre-burned Xpander EPROM's on Ebay, which is doable (USD 65 ex shipping it seems).

I am going to try swapping out the CPU's before I move on to the OS EPROM's.

Cheers, Jacob

Re: Xpander intermittent boot failures, hangs, memory loss

2016-07-06 by skoteinos@...

Hi all,

It has been quite a while now since my last Xpander crash/garble incident and I am starting to believe (knock on wood) the problem is fixed. The last thing I did was remove and re-insert the CPU's (in anticipation of new CPU chips arriving in the mail, to see if I had the right tools for the job). I find it hard to believe that improved anything. However, while fidgeting with the CPU's I also noticed a half-loose ribbon connector on the far left connecting the voice board to the controller board. (See attached picture for the ribbon cable I am talking about.) I pushed the connector back in.

My best guess of what happened is now that when I did work on the transformer (which is all the way on the right in the chassis) this ribbon cable somehow got pulled loose, causing intermittent connection problems and hence crashes. It sounds vague but less so than 'pulling the CPUs out of their sockets and reinserting them fixed the problem'. It also paints me as a fool for creating the problem in the first place, but I would rather be the fool who unseated a connector than having to chase down a mystery component failure.

I hope this concludes this thread (again, knock on wood). :) Thanks for the help and encouragement Bob!

Cheers, Jacob

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Re: Xpander intermittent boot failures, hangs, memory loss

2016-07-29 by skoteinos@...

A little follow-up: few issues since my last post but the other day I had a crash, and another failure to boot (no flashing lights this time). Because I already ordered replacement 68B09 CPU's I just went ahead and installed those. There was no memory corruption afterwards.

This leads me to suspect that the ribbon cable from the voice board to the pot board was not to blame after all...

Maybe it was a CPU issue all along? Who knows. Posting here to help others who might encounter the problem.

Cheers, Jacob

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