Re: Help! The Source is killing me!!!
Posted: Thu Oct 13, 2016 7:04 pm
Sorry, I haven't checked the forum in a bit. Made a little reverse progress (read as collateral damage) during my last attempt and I had to walk away from it for a while. While replacing an IC I seemed to have created another problem...now I have very little signal and a lot of noise coming through. I have a feeling something on the synth board was unhappy with my fiddling. I'll have to chase that down, but I still have the membrane issue to fix first.
To answer your questions, I have re-seated just about everything in there that I can with no change. As for testing the membrane, I did figure out that it was a matrix and tested it accordingly. First I mapped it out and made a spreadsheet showing the working and non-working buttons...hoping it would reveal a pattern...it didn't. Then I purchased a couple of spare flex circuit sockets and perf boards and made extensions so I could plug the flex cables into these, connect to my meter and check continuity and resistance across the contacts for each button...nothing useful here either. Then I connected my meter to the leads of the diodes and resistors for each line and ran through the matrix again...both with power on and off, to make sure the button press was getting through to the rest of the circuitry...which it is. As much as I feared it was a bad membrane, at this point I would have preferred paying the $200 for a replacement.
I figured it was a scanned data/address system, just haven't figured out how to test that, so your input helps. By 'sync the scope with the read line', I'm assuming you mean trigger the scope off of the read line signal??? I'm an EE, but I'm a power systems guy so electronics and processors aren't my strong suit.
I'll probably jump back into it soon and I'll try looking at the components you mentioned (I've already purchased replacements for them anyway...just trying to minimize soldering on the board and I don't remember if these are socket mounted).
Admittedly, I haven't fully sorted through the logic side of things, but I was starting to wonder if I had a processor or RAM issue...although everything else functions so I suppose that's less likely.
I appreciate the assistance.
To answer your questions, I have re-seated just about everything in there that I can with no change. As for testing the membrane, I did figure out that it was a matrix and tested it accordingly. First I mapped it out and made a spreadsheet showing the working and non-working buttons...hoping it would reveal a pattern...it didn't. Then I purchased a couple of spare flex circuit sockets and perf boards and made extensions so I could plug the flex cables into these, connect to my meter and check continuity and resistance across the contacts for each button...nothing useful here either. Then I connected my meter to the leads of the diodes and resistors for each line and ran through the matrix again...both with power on and off, to make sure the button press was getting through to the rest of the circuitry...which it is. As much as I feared it was a bad membrane, at this point I would have preferred paying the $200 for a replacement.
I figured it was a scanned data/address system, just haven't figured out how to test that, so your input helps. By 'sync the scope with the read line', I'm assuming you mean trigger the scope off of the read line signal??? I'm an EE, but I'm a power systems guy so electronics and processors aren't my strong suit.
I'll probably jump back into it soon and I'll try looking at the components you mentioned (I've already purchased replacements for them anyway...just trying to minimize soldering on the board and I don't remember if these are socket mounted).
Admittedly, I haven't fully sorted through the logic side of things, but I was starting to wonder if I had a processor or RAM issue...although everything else functions so I suppose that's less likely.
I appreciate the assistance.