OBERHEIM SYNTH

Hi Rich,
    There are many CMOS chips in this synth.   On my schem, U164 is a 6116 SRAM chip.I don't know exactly how the MIDI kit is set up, or what parts it wants on the MB, so it's toughto answer your question. But assuming that it has its own SRAM and EPROM, then probablyit wouldn't be using U164.   Removing that chip would reduce the load on the data and addressbuses.   There may be a timing problem that is fixed by leaving it in place.   Every so often 
the wrong data is latched somewhere when the right (wrong) conditions happen.   If you want to 
try to learn more, assuming that RAM chip is not used, you can bend out data and address linesindividually and maybe find out which ones are helping to solve the problem.  But it may be more 
than one.   Also, you can only bend the pins so many times before they break.  Your scope probecan also be used to add capacitance to a signal.   You can remove that chip, and then try probing the 
pins of the socket one by one.  If it's just one signal that is making the difference, you might find 
it that way as well.
    If you do leave that SRAM chip installed, check with your scope to make sure it is not 
being selected.   Trigger the scope on the high to low edge of chip select and you should not seeit triggering.
     Bob

      From: "richtrix@... [oberheim]" <oberheim@yahoogroups.com>
 To: oberheim@yahoogroups.com 
 Sent: Thursday, March 19, 2015 6:25 PM
 Subject: Re: [oberheim] Finding Clock frequency of my OBXa