Oberheim Xpander Problems, "Voice Processor Malfunction"

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Oberheim Xpander Problems, "Voice Processor Malfunction"

Postby peterkohlmetzmoller » Sun Feb 17, 2013 8:42 pm

Dear all users of the vintagesynthforum, and especially Oberheim Xpander users.

I have a unbearable problem with a recent bought Oberheim Xpander, Japanese version.
So, 3 months ago I bought a XP-1 from a japanese ebay-seller for a huge amount of money (at least for me) - In the sellers announcement it said "US", "Professionally Serviced", so i thought, this it the one, and I clicked and bought.

Sadly though, when it came here to Denmark, some weeks after, it had the infamous "Voice Processor Malfunction", which leaves the synth muted, and unplayable. Upon opening the unit, i found out that this is one a japanese versions, though not a late one, as it was produced in 1986.
After hours of noodling around, ressetting (clearbutton+swith power on operation) frustrations and so, I tried to change the 40p ribbon cable, which connects the two processors, as my research deep in old internet fora's had told me that something between the 2 processor blocks for the communication between them. And it didn't work any better, though sometimes it feld like, that that was the problem.
The unit is extremely unreliable, but powers up as it should, and sometimes, almost out of nothing, the unit works, or at least for 10 minutes or so, until a new "Voice Processor Malfunction" occurs. When the unit works, it can easily autotune itself, and all functions work flawless.
The unit has not been professionally serviced, or re-capped ever (though the seller told me so) and since this is also something i have found in a lot of the older entries on different forums, this might be something I would have my tech do.
Has anybody here experienced something like this?
Has it somthing to do with the IC between the processors, or the processor itelf maybe?
It seems like the digital connection between the two processors is very buggy, and I simply don't know how to repair it.
By the way, the sellers ebayname is "awakewalk", and has as I write 3 XP-1 for sale on ebay, interestingly with the same pictures as on my unit. Bad buisness, very very bad actually!
Help will be greatly appriciated, as this in many ways, was a dream-come-true-buy, and now, I am just very frustrated and unhappy, having used so much money, and time on something that doesn't work.

All the best, Peter Kohlmetz Møller.
Last edited by peterkohlmetzmoller on Thu Feb 13, 2014 7:46 pm, edited 1 time in total.
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Re: Oberheim Xpander Problems, "Voice Processor Malfunction"

Postby schmidtc » Sun Feb 17, 2013 10:12 pm

Welcome to VSE Peter,

That's awful and I'm really sorry to hear it. That guy charges very high prices and people pay it thinking that a professional dealer is less risky. Lots of people put love and care into maintaining their instruments, which remain only half as valuable because they're not sold by a dealer.

The fact that it works sometimes is promising. It may just be a bad connection, and when things expand thermally it makes contact intermittently.

Does the service manual give any specifics? Have you tried pushing down on the processor chips? There could be a contact issue with the socket. A small shot of residue free contact cleaner (not de-oxit or anything lubricated!) is worth trying around the sockets and connections, in case oxidization is the cause.

Consider joining the xpantastic yahoo group, people there have a bit more expertise.

Good luck!
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Re: Oberheim Xpander Problems, "Voice Processor Malfunction"

Postby plus321 » Sun Feb 17, 2013 11:11 pm

I'm curious, when it does work for normal for 10 minutes, does the pitch fluctuate on the voices?

When I bought my xpander, it worked fine, but would not pass the tunings and so the voices would be muted. When I unmuted them the pitch would fluctuate on it making it sound kind of sickly.

I just recapped the power supply and it was fine ever since. I am not a tech, but my first instinct on something this old is to recap the power supply. If it fixes it or not, it almost certainly needs it.
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Re: Oberheim Xpander Problems, "Voice Processor Malfunction"

Postby ppg_wavecomputer » Thu Feb 21, 2013 11:54 am

I´m afraid I can´t help you either but why purchase an instrument as expensive as this if there are plenty of these around in Germany (okay, there might be nicer neighbours but... ;) ) or elsewhere in Europe?

I don´t know where you are located in Denmark, but if the idea of driving to Hamburg doesn´t terrify you, I can put you in touch with a great technician there who might be able to help you out. You might also want to turn to Kenneth Abildgaard over at www.theppgs.com as he´s a countrymate of yours and may know some capable techs in Denmark.

Stephen
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Re: Oberheim Xpander Problems, "Voice Processor Malfunction"

Postby rikusk » Sat Feb 23, 2013 6:25 pm

The 68E09 on voice board may be defective. I had one Xpander on repair and it had very similar issues. After testing all parts between two CPUs I swapped the CPU from Rhodes Chroma CPU board which I had lying around. The new CPU did the job.

The same Xpander (which had multiple problems, failed display driver etc.) didn't go through the autotune, missing voice or two. The VCO or PW failed on voices 5 and 6 but not always on similar pattern. Reflowing all solder joints on trouble voices fixed the problem.
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Re: Oberheim Xpander Problems, "Voice Processor Malfunction"

Postby sam » Sat Feb 23, 2013 9:15 pm

I have serviced Xpanders but never seen this problem, If it's a bad solder joint then freeze spray around the suspect component can give clues on those matters.
I don't think recapping will sort this.

Find someone who has worked on one where you live...

But good luck and don't give up...
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Re: Oberheim Xpander Problems, "Voice Processor Malfunction"

Postby peterkohlmetzmoller » Thu May 09, 2013 4:15 pm

rikusk wrote:The 68E09 on voice board may be defective. I had one Xpander on repair and it had very similar issues. After testing all parts between two CPUs I swapped the CPU from Rhodes Chroma CPU board which I had lying around. The new CPU did the job.


Thank you guys. Really apreciate it. I guys the best option is to try to swap the voice processor, the motorolla 6809E, I think I have found a a place to buy it. In the japanese version none of the chips (except the voices) are in sockets, so it will probably kill the old one, but i'll give it a try, and maybe buy a 40pin socket for the processor while I'm at it.
The synth is still at my tech's place, so i'll send him these nice replies from you.
If anybody has any other input, it would be greatly appreciated.
My tech measured on the PSU, he said it was perfectly showing the right voltages, so, def. not a problem there. It's gotta be between the IC's or the CPU's somewhere. I'm sticking with the idea of a bad processor, I wish to god it willl solve it, I simply love this monstersynth. rikusk; What condition was your synth in alike, same issues?
All the best from Peter :-)
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Re: Oberheim Xpander Problems, "Voice Processor Malfunction"

Postby synthparts » Fri May 10, 2013 2:13 am

I hope this seller is at least paying for all repairs. I would have returned it for a full refund if he said it was a US made version and it turned out to be the Japan made one...

By the way it is easy to tell which is which by looking at the rear. The US version has the jack labels above the jacks and the Japan version has them below...
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Re: Oberheim Xpander Problems, "Voice Processor Malfunction"

Postby peterkohlmetzmoller » Sat May 11, 2013 1:20 pm

Yes, you are right. I found out right when i opened the package... I guess my research before hand wasn't good enough, but then again, when you pay 3200$ for a functioning xp-1 it's suppossed to be working perfectly, right? I trusted him, also because of the pretty high price.
My problem is that I waited contacting him untill the unit wasn't functioning like it should. In the beginning it seemed to work fine, for a couple of days, and then the voice processor malfunction started to occur, I contacted him after 14 days or so. I have been in touch with him, and he wrote that he would consider paying the repairment, but it's pretty damn hard to do business with someone literally on the other side of the earth.
This issue has been a pain in the ass, but i think there is still a tiny bit of hope.
Thanks for your input people, it's so great to have these oldschol internetforas around when help is needed.
Your thoughts are still greatly welcomed and appreciated :-)
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Re: Oberheim Xpander Problems, "Voice Processor Malfunction"

Postby peterkohlmetzmoller » Sat May 11, 2013 1:37 pm

Here is something in the operation manual.
DOnt know if it makes sense, but the last couple of lines mentions what seems to be the problem.
Image
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Re: Oberheim Xpander Problems, "Voice Processor Malfunction"

Postby peterkohlmetzmoller » Thu Feb 13, 2014 7:46 pm

SOLVED!!! :D :D :D :D :D :D :D

Hello! Very good news for anybody with this sort of problem.
It was the very chip itself, the voice processor, the 68B09EP on the voiceboard that was going nuts.
It's not a job for every diy tech, the chip has 40 very small pins, and its easy to get frustrated and trying to pull it out, which is a bad idea.
If you are not good at desoldering, it's def. a job for a skilled technician.

I am very happy, now i can fire it up and play, whenever I want to. Such a beautiful sound!
Thank you so much for your help everybody!!!

All the best, Peter
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Re: Oberheim Xpander Problems, "Voice Processor Malfunction"

Postby peterkohlmetzmoller » Thu Feb 13, 2014 7:50 pm

rikusk wrote:The 68E09 on voice board may be defective. I had one Xpander on repair and it had very similar issues. After testing all parts between two CPUs I swapped the CPU from Rhodes Chroma CPU board which I had lying around. The new CPU did the job.

The same Xpander (which had multiple problems, failed display driver etc.) didn't go through the autotune, missing voice or two. The VCO or PW failed on voices 5 and 6 but not always on similar pattern. Reflowing all solder joints on trouble voices fixed the problem.


YOU HAVE SAVED MY OBERHEIM XPANDER. Thank you so much rikusk!!! :agree: =D> =D>
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