Since system 9 MPU boards are getting more and more rare I am contemplating performing the MOSFET upgrade to the lamp matrix on the MPU in my Space Shuttle. My board was purchased NoS about 5 years ago and it has the cement resistors, recently I had an issue with some controlled lights and while troubleshooting I noticed that two of the resistors were getting extremely hot and one had almost backed its way out of the solder point creating a poor electrical connection. I have tested, cleaned and re-soldered the resistors back in place but there has been some heat transfer and discoloration on the board. For obvious reasons I want to remedy this issue so the board lasts for many more years. I am no stranger to board work but I am hesitant until I get some feedback from some others who have successfully performed this upgrade as I have seen two methods one using jumpers in place of the resistors and another method lowering the working voltage using 1k ohm resistors. If you have performed this upgrade on a system 9 MPU in particular please give your feedback, pictures, materials list or links to existing documentation for this procedure if possible. TIA!

Bump

I appreciate the feedback guys! Here is another idea, since there is an issue with excessive heat on two of the channels another idea I have is installing a larger resistor or even attaching a heatsink to help dissipate the heat, if I leave the board as is and play it as little as I do the board will last a few more years before the heat does irreversible damage at those locations. I've even considered moving all the matrix resistors off board to eliminate the possibility of heat all together. Just curious what others have done in this case. TIA!