[sdiy] bizarre xpander behavior

[jays at aracnet.com]

klosmon,

If you haven't done it yet replace the battery and reset all the patches. If it isn't bad its time to be replaced since the unit could be as old as 15-20 years.

Check the switches on the front panel. The plastic overlay shinks and can bind the keys causing a key to stick down. That can cause odd problems.

Also Oberhiem has had a lot of problems with sockets. Might try reseating some of the chips. Especially in the computer and memory area.

Put a scope on the power supply. Even though you may be getting volts they may not be clean. The caps are probably getting old and tired too. Also check the power at the memory and cpu chips with the scope.

Jay S.

klosmon wrote:

> I've been working on an Xpander which has been exhibiting some puzzling 
> behavior.  Periodically, it will not complete its power-up 
> cycle;  eventually, when it does power up after several tries, all patch 
> names are missing from the display (even though the patches themselves are 
> still in place).
> 
> I've run through the service diagnostics (RAM, ROM, display, etc) and 
> they're all good; I've measured the power supply rails, and they're 
> consistently good (even after being on for several hours);  I've checked 
> the PUP memory protection circuit, and it's functioning correctly.
> 
> Can anyone think of something I'm missing?
> 
> Thanks.
> 
> ~GMM
>