I got an IBM PS/2 Model 56 486SLC2 computer off eBay for a really good price but it clearly has a problem. When you plug it into power a high pitched and fairly loud whining noise comes from the power supply and the system doesn't respond to the power button. What could be wrong here? Obviously something isn't right in the power supply, but what?
Shorted! Don't keep trying other wise PSU finally die. You WILL need a multi-meter to determine mother board is shorted or the PSU by probing the power connectors on motherboard then power supply's.
Otherwise bad capacitors inside PSU, open it up and look.
Cheers,
Great Northern aka Canada.
pentiumspeed wrote on 2020-04-13, 21:22:Shorted! Don't keep trying other wise PSU finally die. You WILL need a multi-meter to determine mother board is shorted or the PSU by probing the power connectors on motherboard then power supply's.
Otherwise bad capacitors inside PSU, open it up and look.
Cheers,
I figured it was something like that, I've got an old Mac (Mac 128k that was converted to a Plus back in the late 80s) with a faulty analog board that exhibits similar behavior if you try and turn it on, which I naturally only did once.
The power supply on these machines is this ridiculous long thing so that's going to be fun to troubleshoot.
EvieSigma wrote on 2020-04-14, 00:09:pentiumspeed wrote on 2020-04-13, 21:22:Shorted! Don't keep trying other wise PSU finally die. You WILL need a multi-meter to determine mother board is shorted or the PSU by probing the power connectors on motherboard then power supply's.
Otherwise bad capacitors inside PSU, open it up and look.
Cheers,
I figured it was something like that, I've got an old Mac (Mac 128k that was converted to a Plus back in the late 80s) with a faulty analog board that exhibits similar behavior if you try and turn it on, which I naturally only did once.
The power supply on these machines is this ridiculous long thing so that's going to be fun to troubleshoot.
What I said is, reason is the PSU is still working but driving into overload through a output circuits (cold side) either in PSU or motherboard that has a short somewhere, find that short with your multi-meter as I instructed you.
Cheers,
Great Northern aka Canada.
unplug the power supply from the motherboard, try again. Shorted tantalum caps are a common thing.
It is a mistake to think you can solve any major problems just with potatoes.
I also have a power supply, however this is an ATX one, that sometimes (randomly) starts making a whining noise. It *says* to be a 750W PS which I highly doubt, because is a crappy chinese one and also because it has very few connectors (4-pin for the CPU on newer boards, an additional 4-pin to make a 24-pin connector, standard 20-pin, 2 plugs for SATA drives and 2 molex for IDE drives, that's it, no floppy or anything else). Is the whining noise a sure signal of a short? Sorry for hijacking the thread, but it kind of seemed on-topic.
luckybob wrote on 2020-04-14, 02:16:unplug the power supply from the motherboard, try again. Shorted tantalum caps are a common thing.
Yeah, I did that and blasted all the connections with contact cleaner. Made no difference.
No no...
Cannot do anything till you have multi-meter and check the resistances to find the short. Not voltage, not cleaning the connectors.
Cheers,
Great Northern aka Canada.
pentiumspeed wrote on 2020-04-14, 15:04:No no...
Cannot do anything till you have multi-meter and check the resistances to find the short. Not voltage, not cleaning the connectors.
Cheers,
I did that before I actually tried the power supply, since the computer had clearly experienced some exposure to the elements from its internal condition.
If the psu still whines when it's completely disconnected, it's internal to the unit.
If that is the case, there are like 3 things that can go wrong.
1. Something inside is physically shorting.
2. Bad caps
3. Blown power transistors
My bet is on #2
It is a mistake to think you can solve any major problems just with potatoes.
