The Tower models seem to use a lot of interchangeable components such as floppy drives, power supplies for certain models and specifically CD ROM sled assemblies. However the very first FM Towns towers have used a totally different power supply. Luckily I bought a Model 2 and have made a bulletproof solution.
This will only work on the MODEL 1, MODEL 2, S1 AND S2. It should be the only FM Towns tower models that don’t natively have a SCSI socket in the back as you require expansion card. If your power supply looks like the one below then you’re in the right place.
So Start by disassembling the power supply card. There are a few screws like everything. Notice the D-Sub connector with approximately 14 wires coming out of it. This is your interface to the motherboard. Safely desolder the wiring harness from the PSU card and the Fan wire. The two fan wires might be in a plastic casing on the metal PSU shield. Work around and cut it out.
You should now have this. Cut the yellow looking plastic around the wires since you need all the wires free spread.
To assemble the card it’s quite simple. The silk screen should give a good guide just like the photo below. This might get revised at a later time so you can place an MINI ATX power supply inside since I believe it could be more cost effective.
You should now add your 120watt pico and solder wires to the ACDC converter. I usually bridge two points together and then add the wires just like in the photo.
Solder the RED wire to the 12V hole and the BLACK wire to ground from the fan.
For the D-Sub connector the following pins are the proper ones. Physically look at the connector. In the upper left, upper right, lower left, and lower right the pins are labeled. Unfortunately I didn’t take a high resolution photo of the connector but I have the proper pins written down. However here is a photo. I assure you it’s visible with the naked eye.
You can also use a multimeter and measure continuity from the motherboard (CPU motherboard) voltage pins which are clearly labeled near the SRAM and CMOS batteries to the pins of the backplane circuit board on the bottom. This is what I did.
- 5, 6, 11, 12, and 13 are GROUND
- 4 is -12V (for sound)
- 10 is 12V
- 1, 2, 3, 8, and 9 are 5V
- 14 is the Power button so on the PCB, it will be “ON-OFF”
- 7 is OS-OFF to shut down the PC via TOWNSOS.
You should now have a mess like the following below. In the photo I have the screws on the ACDC converter. Don’t add them yet.
On the metal PSU shield, cut the plug. In the photo you will see I also stripped the wire a bit. Tin the wires and solder them back into the receptable.
This is ultimately what you want to do with those wires. You now have use of the receptacle but keep in mind that it’s your countries voltage.
IF YOU ARE IN 220V COUNTRY DO NOT PLUG YOUR TOWNS CRT INTO THIS SOCKET UNLESS YOU’RE ON A STEPDOWN
Now solder the wires.
At this point you’re done with the major assembly. So add your screws to the ACDC converter stand-offs and reassemble the metal PSU shield. Remember to route the fan wire!
Critical you have that fan wire routed properly.
Now enjoy reviving your Generation 1 FM Towns.