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This is great information. I have two PM7100 boards. One with similar inconsistent booting issues that you described. My other board used to boot fine, but after sitting for a year now refuses to boot. I will order some capacitors today. Thx.

I ended up buying a replacement motherboard. I bought a 800k motherboard and installed the ROM from the FDHD board. So at least it is reading the 1.4mb floppies. I am guessing there is a broken trace near the RAM, CPU and BBU chips. I was looking at one of these MacSE reloaded boards to play...

I had a similar situation last week with a PB170. There's really no easy way to do it other than to gently pull the screen bezel at the same time you try to undo the screw. That will place some pressure on screw and enable to turn it a bit. It will take a little time and patience. The plastic...

I am still researching, but I buy my sockets from Phoenix Enterprises for a while. They have great prices. I will be buying the CPU and FPU sockets from them and was looking for the PDS socket. I was thinking of just a 3 row snap header, but there are some options. Here's a link for their...

Very nice. I just ordered some boards today. Looking forward to building. Thanks for the inspiration and the write up.

Congrats!

I am certainly interested in your repair too. I have a similar issue with my Mac IIx motherboard with no nubus. I don't get a chime (sound chip issues), but my CPU gets warm and it seems to boot, but no video. My nubus video card is also showing activity as can be seen by my thermal camera...

Start with the Nand Gates UJ18 (startup) and UI18 (shutdown) and search for broken traces due to the leaky capacitors near by. Here's image of the Startup circuit. Also a link to Doug Brown's write up on the Mac IIx start up circuitry. Even thou there is a difference with the IIx and IIfx, he...

Thanks, I will recheck my solder joints.

I do have a question about the proper chips to use with the SIMMs. I bought the PCB's over a year ago and finally had the time to build the SIMMs. I bought the 72pin SIMMs with the KM41C16000BK recommended on another post. But noticed that the built chips I also purchased are using the...

Yup, I replaced the screw that had corroded from the cap goo. Unsure on the size, I have a stash of old Mac parts and screws. I think it's a screw that holds the PDS expansion bracket on the MacSE. I'm glad it worked and glad I found your post on this card.

This was a great write up and an inspiration for me to upgrade the memory on my video card. I used the same value, but a higher voltage capacitor for my card. Thx.

Nice work!

I also replaced the video board on my troubled SE. Maybe that may help. It's not very costly to check. https://www.ebay.com/itm/295548281444

I just went through with the same issue on my MacSE FDHD recently. I recapped the analog board and replaced the same IC and the line remained. I ended up recapping the power supply I finally got a full regular screen. A few weeks later I got a checkerboard screen which was a motherboard issue...

Repaired with a replacement motherboard. I purchased a eBay MacSE 800k motherboard. After a test boot, I placed the FDHD ROM and SWIM IC's on to the replacement board and it booted. This means the ROM/SWIM chips are good and that there is a broken trace on the board, possibly between the BBU and...

This was a great read. I have a working MacIIx and a spare motherboard I just can't seem to get to boot (startup/shutdown circuit if fixed, just no boot chime and no video). It is frustrating not having a proper schematic.

I went through all the solder joints on the back of the board with my soldering iron and got the same result. horizontal lines. I also tried using some 30 pin 9 chip parity 70ns FMP SIMMs I bought on eBay that are supposed to be for the MacSE. I got a checkered screen pattern and no boot...

Well that didn't last long. I swapped the motherboards and the FDHD board went back to no chime and lines on the screen. I am going to reflow some of the solder joints on the board. It must be a connection issue.

Okay, Weird one. I have another MacSE 800k and decided to try the MacSE FDHD motherboard in the 800k case. It booted without issue. I placed the 800k motherboard in the FDHD case to check if maybe it was the analog board issue. It booted too. Unsure what caused the issue, but if place the...