View Full Version : PC/XT 130W PSU problems.

February 5th, 2014, 01:16 PM
Hi all,

I've just bought a 5150 case from ebay, it had a dead 16/64K motherboard in it but as I'm intending to build my PC-RETRO board in there that's not a problem.

However the PSU included with the case is only a 63W one and the casing seems to have a load of surface rust so I don't really want to use that one. I have what I thought was a working 130W PSU from an XT that fits in the case perfectly but seems to have a problem.

The first couple of times that I powered it up, it seemed to work OK a hard drive attached to it spun up and the motherboard & video card powered up and I got a flashing cursor in the top lefthand corner of the screen. However now when I try and power it up the fan in the PSU comes on but nothing else seems to happen the hard drive does not spin up and I get no signs of life from the video output.

Does anyone know what could be the problem here?

Alternately does anyone have a suggestion for a workable solution I did think about the possibility of maybe fitting an ATX PSU inside the PC PSU's case, but I'd like to retain the big red switch :) Failing that is there anyone that can sell me a UK (220V) PC/XT PSU for a reasonable price.



February 5th, 2014, 02:01 PM
Try the Minimum diagnostic tips on Modem7's site http://www.minuszerodegrees.net/5150_5160/MDC/minimum_diag_config.htm

February 5th, 2014, 06:13 PM
IBM's XT and AT power supplies required a rather heavy load in order to run. In fact, floppy-only IBM AT models came with a dummy load to mimic the electrical load that a hard drive would have. So even with the XT power supply, just the motherboard and one floppy drive might not be enough load to let the power supply run well. Try plugging in a hard drive (preferably a 5.25 inch drive) even if it isn't being used by the system.

February 5th, 2014, 06:56 PM
Realistically speaking, it is unlikely that you ever exceed 63W of load with a system like that.
If you plan to use an ATX PSU, you are also going to need a ATX to AT converter. But things are not that simple. The AT PSU is pretty much designed for the systems of that time. When ATX models arrived, there was a constant increase for the demand of the +12V line and that one is where most of the ATX PSU wattage is for. An AT mainboard will mainly draw power for the +3.3V and 5V lines. ISA slots might also want the -5V line and you might have a problem with the -5V if you use an ATX to AT converter.
Personally I would use that 63W unit. I would see if the system works, maybe plus a power meter to check how much power it actually needs and then decide on what I do. Back at those times, there were little to no power-saving features, so while the system is idle, it consumes pretty much the same power as it does when loaded. So if you just measure the power it draws from the wall plug, you just know what it is going to need.

February 6th, 2014, 03:54 AM
Here is what I would suggest

First, buy this


You will also need a Security Torx Screwdriver like the one pictured below, so you can open the XT PS. You should be able to find them at a hardware store


When you get them...

Open up the new AT PS. You will notice the guts is much lighter and much smaller. Take pics, especially of the wires going to the external power connections, and the wires going to the switch.

For the wires going to the power connections and the wires going to the switch, you have 2 options:

1) Easy option. I suggest you use this option. If you do, you actually do not even need the soldering iron. You can cut the wires (as long as possible). This will allow you to simply connect the wires by twisting them together and then use either electrical tape or heat shrink to cover the joined areas. Reference the pics you took of the 5160 and new PS to see which wires to join.

2) This is the less clutter, neater option, but it is more difficult. You must unsolder the wires at their respective connections. Unsolder them at the pins on the for the power connectors and switch, NOT at the board. Now solder the wires from the new PS to the power connectors and switch. Reference the pics you took of the 5160 and new PS to see which pin to solder which wire too.

The screw holes for the new PS board will NOT line up with the 5160 holes. You *could* drill holes in the case, but I opted to simply stick velcro squares on the bottom of the PS board and on the case. You may need to "build up" the squares, i.e. stack them to create some height. You may also need to cut them in half. They don't have to be placed at the corners of the board. It may be that you can simply use 2 squares at other locations. As long as you can secure the board to the new PS case.