ATX to AT Adapter Problem

[MrCaffeineX]

I am trying to replace the power supply in a piece of embedded equipment running what I believe to be Pentium II era hardware (slot load CPU on a daughter board). The unit has an AT PSU with a P8 and P9 connector.

I have plenty of ATX PSUs collecting dust, but I hardly ever touch anything from the AT generation. I know that the ground wires (black) need to be together when the connectors are plugged in and that is about where my experience ends.

I ordered this ATX to AT adapter: http://www.amazon.com/ATX-Motherboa...UTF8&qid=1427826467&sr=8-1&keywords=atx+to+at When I went to hook everything up, I noticed that the adapter cable has two P8 connectors on the end, not a P8 and P9. Several of the wires are in the same place as the combination P8/P9 connector, but several are not.

I will upload some pictures after I get home. I plan to test the outputs with a multimeter when I get home as well. In the interim, has anyone here successfully installed one of these adapters and does anyone know if the wires being different colors or the connectors being labeled differently makes a difference?

 

[cyclone3d]

StarTech makes good stuff.

http://www.startech.com/Cables/Computer-Power/Internal/ATX-to-AT-Motherboard-Power-Converter-Cable~ATX2ATPOW

I would think that the connectors would be labeled P8 and P9. Maybe you got one that was put together wrong.

I haven't dealt with AT stuff in a long time, so I looked it up.

As long as you have the black leads on the connectors touching each other, you should be good.

http://www.computerhope.com/jargon/p/p8.htm

 

[JoeBob]

AFAIK, AT PSUs weren't used with Pentium II systems. Those use ATX standard. At least the Pentium II mainboards I had were all ATX.

 

[MrCaffeineX]

AFAIK, AT PSUs weren't used with Pentium II systems. Those use ATX standard. At least the Pentium II mainboards I had were all ATX.

That only makes it older then.

I was too tired to dig out the multimeter and camera last night after I got home from work. I'll give it a shot again tonight.

Either way, the plugs are definitely AT-style. I want to make sure the pins are being fed with the right voltages before I power the box back on.

 

[GiGaBiTe]

AFAIK, AT PSUs weren't used with Pentium II systems. Those use ATX standard. At least the Pentium II mainboards I had were all ATX.

I've seen AT style PII motherboards. They were probably made for people with older AT rigs as a cheaper upgrade path so they didn't have to buy a new case, PSU, etc. Just like every generation we have weird boards to allow people to use their older hardware with newer tech.

Though as a word of warning to the OP, if you do end up using an ATX to AT power adapter, you'll have to make sure that the ATX power supply you're using has the -5v rail. Many AT motherboards will not power up or run properly without this voltage.

The -5v rail was removed from the ATX spec in 2003 so finding an ATX PSU with that rail may be difficult if you don't already have one. The easiest way to tell you have a -5v rail is that the ATX power connector will have a white wire on pin 18. If it doesn't have the rail, pin 18 will be empty.

Two solutions to try if you don't have the right ATX PSU:

1) Scour the interwebs for one of those Asia-X brand IEDs that still use the ancient ATX spec with -5v. An old PII system won't draw enough power to cause these to fail.

2) Use a negative voltage regulator to get -5v from a positive voltage. The MAX889T is probably the simplest solution:

http://datasheets.maximintegrated.com/en/ds/MAX889.pdf