Email to Bob Grieb, provider of the Multi-Trak firmware
Hi Bob, it’s been a while since I emailed you so since you asked I thought I’d let you know where I’m at with the Multi-Trak.
Despite being fairly experienced with synth repair i made a couple of noob mistakes. I did the battery replacement and somehow installed the battery backwards, and I’m sure my solder wire dragged across several points on the board as I was installing the battery. So I’m worried that I could have blown up a CMOS IC or two. I reinstalled the battery correctly shortly afterwards.
The other mistake I made was doing the battery drain mod and the ROM mod at the same time – now the synth is totally dead on power up. I have a troubleshooting strategy though…
I haven’t had much time over the past few weeks but I’m just getting back to it today. The easiest thing to do was put the battery mod back to stock configuration. Still no joy.
The next thing I want to try is put the stock ROM back in, just in case something went wrong with the EPROM I programmed. I suppose I should remove your mod board to do this.
I also suspect the stiff 40-wire ribbon jumper that connects the two panel boards. I have seen these things go intermittent or resistive in old electronics. So with the ROM and battery mods normalized I will replace those, and then I’ll start testing ICs if it still doesn’t work.
Hi there,
I’m sorry to hear about your problems with the Multi-Trak repair, but also thankful that you made them public. I recently acquired a Multi-Trak myself, but the condition of the instrument is still a bit of a mystery as I don’t have a power supply. If it turns out to be ok / repairable, I’m planning to do both the battery drain and EPROM modifications. I’m sure I would have done those at the same time if I didn’t read this. Good luck with the instrument and please keep documenting the repairs!
Thanks. I’m sure it will be simple enough. I have taken lots of pictures along the way but I haven’t posted them because I want to be 100% sure everything is right before I share.
Did you have a chance to finish the battery drain mod? If so did you use midi to reprogram factory setting? I am tackling this project and any incite would be highly valued! thanks.
I did indeed use MIDI to reprogram factory settings. I had trouble with my mods. Still waiting for a chance to get back to this – Multi-Trak is apart on the bench….