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First time poster. I recently acquired a DX7ii FD w/ Grey Matter Board. The seller told me it would load patches and play but not save (typical). The previous owner installed a battery holder and new battery. I thought a factory reset would do it. But I loaded all the ROM's and it played fine, but still didn't save settings when turned off.
I took it apart to inspect. The battery is giving around 3.1V so that was good. I looked at the wiring and noticed all the wires were correct excet the Brown (R/W) wire. It was soldered to the RM6 resistor array underneath the correct IC12. I removed the wire and correctly attached it to Pin #1 of IC12.
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Upon tuning it on I see this.
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I was originally freaked out but when i removed the brown wire it went back to the original state (functional but not saving). Anyone have any ideas what might be going on?
P.S. Sorry for the links. I don't know how to embed images.
Posted : 21/09/2026 12:31 pm
Welcome to the forums!
You may be a new poster but you appear to have a good deal of experience since you took the time to provide some specific info about your problem. That makes it much easier to try to help.
As step #5 of the of the installation section of the manual shows (p.65 of the grey matter manual) the brown wire is the R/W wire and should be soldered to pin #1 of IC12.
CAUTION - it is easy to misidentify pin numbers since what may appear to be pin #1 may NOT BE pin #1 depending on which side of the board you are looking at. If you count the pins from the bottom but use the top-side orientation the wire may have been soldered to the wrong pin. That wrong pin would be an address or data line and could cause your problem.
#1 - double check ALL IC's, wires and traces to make sure that all pins are seated and there are no solder bridges.
#2 - Check the continuity of Pin #1 of IC12 and the trace (not the pad) it is supposed to connect to to make sure the pad isn't broken. if the previous owner moved the wire to RM6 maybe it was because they lifted/snapped pin #1 of IC12. If there is no continuity to the trace itself it could mean the pad is broken or cracked.
#3 - double check that you have correctly identified pin #1 - it is sometimes marked with a square solder pad on the PCB rather than a round one.
#4 - double check ALL solder joints and traces - they are really tiny so it is easy for an experienced person (e.g. previous owner) to create a solder bridge between two pins or traces. If you see, or suspect, any use a 'solder sucker' to clean both joints completely and use a very fine tip on your solder iron/gun and re-solder them.
Are you soldering from the 1) top, or 2) bottom of the DM mainboard?
Does pin #1 have a square or round pad?
Posted : 21/09/2026 5:20 pm
Topic starter
Thank you for the excellent response. I will check all of this and report back. I originally soldered it to the back. I guess it is possible I created a solder bridge between two pins. Right now it is on (what I believe to be) Pin #1 of IC21.
I wish I knew how to post pictures. I looked for a manual on the forum for posting images but can't find one.
Posted : 21/09/2026 5:30 pm
To post pictures upload to imgbb then copy the link for the image and paste that into your browser to follow that link. Then right click on the image that shows up and pick "copy image link" or similar for your browser. Then paste that link into here and it will create an inline image.
Current Yamaha Synthesizers: Montage Classic 7, Motif XF6, S90XS, MO6, EX5R
Posted : 22/09/2026 4:16 am