Very strange and annoying problem with my A500 PSU

[AmigaMance]

Hello.
 I'm using an original A500 PSU for my Amiga 1200 and it has served me well well for many years.
 Just 3 day ago, i experienced a very strange problem:
When i switch on the PSU, the power led of the Amiga 1200 flickers like MAD (not dimming like in a guru, but flashing very fast) and i hear a constant noise from the PSU that sound like an electric discharge. My Amiga doesn't boot of course.
 If i switch ON the PSU without plugging it to the Amiga, i don't hear this clicking sound, thus i suspect that it's a problem from the part of the circuit which is beyond the secondary coil of the transformer.
 I thought that dirt was causing a capacitor to discharge rapidly, so i opened it and cleaned it with a big amount of alcohol and cotton pads. After i cleaned it up, the PSU was functioning ok again and so did the Amiga!

 After a whole day of Amiga experience, i switched off the PSU and went to sleep with the confidence that i have solve the problem...
 The other morning i switched the PSU and here it was!! Rapidly flashing led and the discharging-like sound from the PSU.. :-(
 I followed the same cleaning procedure.. PSU started to work ok again.. went to sleep.. the other day same problem!!, And so on, and so on, and so on.
 I feel like i've been trapped into a time loop. What could be causing this?

[Anthomatic]

Maybe it's the power switch itself? The contacts could be worn after years of use, causing an bad connection.

[AmigaMance]

Maybe it's the power switch itself? The contacts could be worn after years of use, causing an bad connection.

 I don't think so, because that would cause the problem to occur even when i have not connect the PSU to the Amiga.

[DrDekker]

If this is the same PSU that you've had connected when experiencing the problems detailed in your other thread (or even if it's not for that matter), just desolder the amiga power cord and throw the PSU in the bin, then connect the power cord to an AT PSU using a chocolate block connector (details on the web) and hide it out of sight.
Although a A500 PSU is better than a A1200 version, it's still pretty poor and just not worth messing around with (unless you really must have the 'brick' enclosure).

An AT PSU will have oodles of power to spare and will be much more reliable.

[golem]

I had exactly the same problem with an A500 PSU and a 1200. Eventually the PSU totally died and I replaced it with a new un. No problems with flickering power light since...

[AmigaMance]

@DrDekker and golem

 Yep, it's the same PSU.. :-) I think i have enough of it and i will exactly what you said. I THINK i have found a temporary solution though: I plugged it, in my spare Amiga 1200 and it worked ok. Then i thought.. let's open my Amiga and clean the area around the power plug.
 Well, it is working right now but who knows for how long. I will hack the cable and attach it to an AT.

 Let's see if the other problem vanishes as well.

[AmigaMance]

Btw, the AT PSU that i'm holding right now doesn't have a Watt rating but the label says:
OUTPUT:  +5v  20/23A
        +12V   8A/9A
         -5V   0.5A
        -12V   0.5A

 Is this enough or i will have to buy a more powerful one? My setup in not too bloaded. (No PCI, USB boards)

EDIT: and OUTLET:
 120/240V ~ 60/50Hz, 1/0.5A
The power network produces 220V, 50Hz here.

[Homer]

Sounds like a bad case of groundhog psu to me  :-o

[motrucker]

You are really playing with fire, using a PSU that doesn't act right. Remember that a psu can easily give the computer too much voltage/amperage/etc., and kill the computer.
Get a new psu quickly!!
 

[AmigaMance]

motrucker wrote:
You are really playing with fire, using a PSU that doesn't act right. Remember that a psu can easily give the computer too much voltage/amperage/etc., and kill the computer.
Get a new psu quickly!!
 

 Well, i have a AT PSU right here. That's why i typed its specs and ask if it's ok or if i should buy a more poweful one.

[jj]

I cant imagine that you would have an AT psu that could not supply enough power. In fact I would say thats fine

[Zac67]

That's a 200W PSU when you'd need a 25W one - easily enough to power an accelerator board, 128 MB RAM, 2-3 hard discs and a DVD burner.

@motrocker
You can't kill anything with 'overamps' - overvoltage can very easily though.

[AmigaMance]

 Neat! Thanks for all the replies.

[rkauer]

Even those half-asset Compaq Presario PSUs (135 W) can give you more power than you'll need in a very expanded 1200.

[AmigaMance]

Ok.
 I have cut off the plug from the A500 PSU and i'm ready to connect it with the pc one. Sorry if this is a stupid question, but i haven't done it before:
 The cable of the A500 has 4 wires + a shield/ground cable that surrounds the other ones, while the cable from the PC PSU has 4 wires. (Actually it has 2 plugs with 4 wires and 2 plugs with 6 wires!)

 My question is, what do i do with the extra shield wire? Do i just short-circuit it with the ground wire?