9401-150 Power Supply Pinout

The PSU pinout of the Model 150 is nowhere to be found on the net. This article should change that.

Connector to Colors

The board has connectors for five cables coming from the PSU. The connectors on the board are labelled 1, 2, 9 (first row), and 10, 11 (second row). All but 9 are mechanically standard 6-pin PC/AT PSU connectors.

All descriptions are taken from an original 150 PSU.

Connectors 1 and 2 are also mostly standard AT pinout.

Pin	Connector
	1	2	9	10	11
1	Orange	Black	Red	Green	Green
2	Red	Black	Purple	Green	Green
3	Yellow	White	Black	Green	Green
4	Blue	Red	Brown	Black	Black
5	Black	Red	Grey	Black	Black
6	Black	Red		Black	Black

Colors mapping

Color	Meaning
Black	Ground
Blue	-12 V
Brown	Unidentifiable
Grey	Unidentifiable
Green	3.3 V
Orange	Power Good
Red	5 V
Purple	Power on/off
White	VFan/-5 V
Yellow	12 V

PSU Replacement

I had successfully replaced the PSU of a 150 with a stock PC ATX PSU. It works. If the original PSU isn't available, this article is meant to help you.

I had an old PSU available, so I could at least in part deduct which wires have which signal. For the sake of replacing a defective PSU, the old one is just an ATX PSU in disguise: AT-style connectors, but ATX function (3,3 V supply, soft power on/off).

If the old PSU is available but defective, it's a lot less work to repair it. Most often, the two primary caps are at fault. Replace them, most often you should be fine.

If you decide to put in an ATX PSU, you need at least four AT style connectors, favorably with wires of at least 20 cm already attached. If you don't have two old AT-style PSUs, you need to obtain connectors elsewhere. I'd better not solder the cables to the connection pins on the board.

In addition, you need a (at least) three-pin header connector for the standby, power-on and accompanying ground signals. I'd recommend to use a 5-pin with mechanical protection against putting it on in reverse.

Finally, just ignore the grey and brown wire connections of the original PSU's header connector. They either are not used by the board itself, or they are not strictly necessary. Also, newer ATX PSUs do not offer a -5 V supply. This is also not needed, just cut the appropriate wire from the connector going to the board.

Caveats

• The new PSU should be able to deliver at least 150 W of power on the secondary side.
  • It's unfavorable to put in a PSU with much higher nominal power, e. g. 500 W or more. The PSU will run with partial load, lessening its efficiency.
• The holes for fixing the PSU neatly match with the holes in the case. Fan has to go to the top (with modern, huge-fan PSUs)
• A lot of thick cable soldering is involved. So you need a proper soldering tool which is able to sustain a considerable amount of heat while maintaining the tip temperature.
  • Take your time. Fiddling with all these wires with different colors should not be done in a rush.
  • Label the new PSU, stating that the cable colors are not to be trusted!

Power Savings

Newer PSUs are more efficient than the old one. The following table shows an example Model 150's power dissipation with the following hardware features:

• 3× 6606 (2 GB, 5400 RPM) disks,
• HP DDS-2 DAT drive, idle,
• IBM CD-ROM drive, idle,
• #2720 combined serial and twinax IOA,
• #2724 Token Ring IOA inserted in ring,
• 192 MB of RAM

Mode	Power dissipation
	Original PSU	New PSU
Standby	3 W
Disks not yet spinning	61 W
Disks spinning	64 W
Idle	73 W
Busy with CPU and disks	85 W

See also

• AT power connector, Wikipedia
• ATX power connector, Wikipedia