IBM Aptiva AT power supply - 3-pin connector? \ VOGONS

IBM Aptiva AT power supply - 3-pin connector?

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First post, by thp

Posted on 2018-10-12, 10:03

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I got my hands on an IBM Aptiva 2168-857 (66MHz Intel 486DX/2). I wasn't able to fully test it yet due to lack of drives. However, it POSTs and I can get into the BIOS setup, but sometimes it just switches off and on again randomly, I suspect (hope) it's the power supply.

Checking inside, the power switch on the front doesn't seem to be a normal AT power switch - it goes (2 wires) to the mainboard, and there's an additional 3-pin connector going from the main board to the power supply. The power connection (power supply to mainboard) seems to be standard AT.

What is the pinout for the 3-pin connector? Would replacing the AT power supply with an ATX power supply (with ATX-to-AT adapter) (and NOT connecting the 2-pin power switch and 3-pin motherboard-to-power-supply) connector work, or do these IBM boards "require" the 3-pin connector to the power supply to function?

Reply 1 of 9, by Elpast0r

Posted on 2019-03-23, 06:44

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I know i'm reviving this old tread, but im having the same problem here 😒 . Aptiva with dead psu... Did you fix the issue? Did you find a way to replace it?

Reply 2 of 9, by Deksor

Posted on 2019-03-23, 09:26

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It's actually a LPX PSU with support of APM. Not really something standard unfortunately ...

The best you can do is to probe the 3pin connector to know if one of them brings some power to the board, and maybe find out what the other two do.

Trying to identify old hardware ? Visit The retro web - Project's thread The Retro Web project - a stason.org/TH99 alternative

Reply 3 of 9, by quicknick

Posted on 2019-03-23, 11:00

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Facing the same problem here, I have a Socket 5 motherboard which I identified as part of IBM PC 730/750 Series. I also found the Hardware Maintenance Manual for it, but the two connectors are only described as:

J38 On/Off Switch power supply connector
J37 On/Off Switch connector

My board sometimes at least tries to start with the above headers not connected, but it never went past the video BIOS message

Reply 4 of 9, by Elpast0r

Posted on 2019-03-24, 08:07

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Thanks for the responses, will look into it! Do you think this can help? I'm affraid i'm not tech-smart enough to use the info.
Source:
http://oldcomputer.info/pc/ps1_2168/index.htm
-----------------------
Power Supply Unit

Power supply unit for this IBM is quite non-standard. The pinout is exactly like AT, but the unit has additional 3-pin connector. This connector is used as a power switch, making the power supply unit run when pins are shorted.
Most cheap ATX power supply units can be used by attaching AT cables to them and connecting the 3-wire connector to the Power on signal according way:

Mainboard edge
--------------------------------------
| [123] [AT connector]
| BATT

Where:
1 - +5V Stand-by
2 - Power on signal
3 - GND

This computer doesn't use large power, and so-called 300W ATX units will usually work... if you don't add more CD-ROM or hard drives.

The only problem may be when turning the computer off, because unshorting the pins will not make ATX turn off. Here, a power switch on the rear of a PSU can be used as well as some logic circuit may be built to adapt PS/1 signal with ATX unit.

Reply 5 of 9, by Deksor

Posted on 2019-03-24, 11:32

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I guess a small circuit could be made out of this, but it may not be worth the hassle

Trying to identify old hardware ? Visit The retro web - Project's thread The Retro Web project - a stason.org/TH99 alternative

Reply 6 of 9, by Brickpad

Posted on 2019-03-24, 14:45

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Elpast0r, I might have the PSU that you need. I will send you a PM.

Reply 7 of 9, by Elpast0r

Posted on 2019-03-25, 15:12

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Brickpad wrote:
Elpast0r, I might have the PSU that you need. I will send you a PM.

Hi! It seems I cant reply as a new member. A replacement psu would be great, problem is I live in Belgium 😀

Reply 8 of 9, by airs

Posted on 2019-09-19, 16:56

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Sorry for the necro, but I want to help folks out who might be searching for a solution to this. I came up with a workaround for using a standard AT PSU and posted it here - Re: IBM pc 330 450dx2 PSU questions

Reply 9 of 9, by Opus7

Posted on 2021-12-05, 09:54

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Elpast0r wrote on 2019-03-24, 08:07:
Thanks for the responses, will look into it! Do you think this can help? I'm affraid i'm not tech-smart enough to use the info. […]
Show full quote

Thanks for the responses, will look into it! Do you think this can help? I'm affraid i'm not tech-smart enough to use the info.
Source:
http://oldcomputer.info/pc/ps1_2168/index.htm
--------------

Mainboard edge
--------------------------------------
| [123] [AT connector]
| BATT

Where:
1 - +5V Stand-by
2 - Power on signal
3 - GND

Thanks! How would you power it on? Connecting the +5V with the power on signal? I suppose not with the GND?

Markus

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