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Can't get ATX power adapter to boot 5150.

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Fire-Flare

Experienced Member
Joined
Dec 17, 2009
Messages
273
Location
Washington State
I'm trying to test the main board, but I don't have a proper power supply.

I'm using one of these to connect an old ATX PSU but it's not booting.

What happens when I ground the green wire is that the hard drives spin, the video card shows its start-up text, and continues showing it until I release the wire. No beep codes.

I know the problem isn't the video card because it works fine in my test board, I doubt it's load-related because I have two hard drives connected, and I tried putting a 1k resistor between the 'power on' and '5v' wires as a pull-up, but that didn't help.

Your thoughts?
 
If the video signon comes up, your system is running. To get there, your 5150 had to go through its POST, locate the expansion ROM on the video card and execute it.

I think you need to look elsewhere for the problem.
 
Fire-Flare said:
until I release the wire.
Click to expand...

It has to be shorted for as long as the PSU is to stay on. As soon as you release the wire and break the shorting, you actually turn the PSU off, which in turn will turn the computer off.

A 'bistable' switch should do the trick.
 
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Note that the 5150 doesn't show anything on the screen when it checks the RAM. The 5160 XT and almost all later systems will show the "memory count", but as I said; the 5150 doesn't. If you have 640KB of RAM in your 5150, checking all of it may take a coupple of minutes, and when this happens you will only see the message left by the video card's BIOS extension.

I suggest you may try to keep it going for a while and see if anything happens. If nothing happens within 5 minutes, then there is most likely a problem somewhere.
 
Fire-Flare said:
That about sums it up. The machine seems to be resetting itself about every 30 seconds. (I didn't time it and don't want to have it run like this longer than necessary)
Click to expand...

If you mean reset as in "screen goes black, then the video display comes up again with the initialization message", then you may start searching for shorted capacitors.
 
per said:
If you mean reset as in "screen goes black, then the video display comes up again with the initialization message", then you may start searching for shorted capacitors.
Click to expand...

I found my watch!

Seriously though, it seems you were right. I removed the board and didn't see anything wrong with it, but a can of air seems to have dislodged whatever was causing the problem Thanks so much!
 
Fire-Flare said:
I found my watch!

Seriously though, it seems you were right. I removed the board and didn't see anything wrong with it, but a can of air seems to have dislodged whatever was causing the problem Thanks so much!
Click to expand...

Nice to hear you got it fixed. It may have been a loose connecton somewhere that migth have caused the problems.

What I meant by shorted capacitors is that the capacitors IBM used tend to break after a while, causing them to act as jumpers (thus shorting the affected powerline and ground). This is more likely to happen if the machine hasn't been used for quite a while, and the climate it has been stored in may also have an effect. The sympthoms of this is that the PSU bails and won't even turn on at all, or that the broken capacitor blows up if the PSU provide sufficient current before bailing.
 
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I used to link people to this one specific page for this, but can't find it ATM. In the meantime here's one that sells it:
http://www.power-on.com/connectors-adapters.html

The site I recall had a tan-yellow background and explicitly focused on PSU conversions of various sorts, AT->ATX, ATX->AT and other connectors to others.
 
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