Sounds like the patch storage RAM is not working somehow. Could be an
address line , a data line, or possibly a bad RAM chip. Probably an easier
way to find the frequency of the clk is to simply locate the crystal. The
frequency is usually stamped into it. There is probably only one crystal,
and it should be pretty close to the Z80. The Z80 clock should be half of
that rate.
You can try removing any chips that are socketed having to do with the
patch RAM and then plugging them in again. Actually, you can just pry
one end up maybe 1/8" or less with a small screwdriver, then push back
down again, then do the other end. Just a little motion relative to the
socket tends to clean the leads, in case they aren't making good contact.
Ground yourself by touching the metal inside the case before doing this
so you don't make a spark from static/ESD.
Bob
From:
"richtrix@... [oberheim]" <oberheim@yahoogroups.com>
To:
oberheim@yahoogroups.com
Sent:
Saturday, March 7, 2015 1:13 AM
Subject:
Re: [oberheim] Finding Clock frequency of my OBXa
Thanks again for that Bob.. unfortunately I am one of those Tony discusses in that post and we tried all of that stuff. At this point I'm just waiting for my little oscilloscope to arrive in the mail to measure pin 6 on the Z80 (I'll be careful). I ordered a scope piece of hardware that connects via bluetooth to my android phone. I'm hoping it works well. My buddy wouldn't let me borrow his and I'm not hauling my board over there.
In the mean time (not that it will matter in the long run) I'm puzzled as to why my memory functions are all the sudden not working on my stock chipset. I can change patches but the sound is completely wack. I can also load my tape backup from before I installed the MIDI kit and the sounds load but they are completely crazy. Manual mode works fine. If I save something to memory it appears to work as the patch will audibly change when written over but the sound that comes out is thing and crazy with super slow attack. Really weird.
Sincerely,
Rich Clarke