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ScuzzBlog: Diaries January 2020

Entry 1st January 2019: Post 01: A500 PSU - What's that burning smell.


A500 PSU - What's that burning smell.
I have quite a stash of busted and broken Amiga PSU units and today
I thought I would check out one of my busted heavy bricks for the
500 and see if I could work out what was wrong. First though I
opened up a lighter weight PSU to check for fuse suitability.

Amiga 500 PSUs are either heavy or light. Not really sure why the
heavy ones or 'brick' as I call them work better in powering kit
with extra added drives, devices and peripherals. These are the
type I use on my A1200s with extra drives.

Anyway I opened up a lightweight PSU and discovered a burn mark
on the board below. This tracks through to two components above.
This was a recent failure which occurred the moment I switched it
on. Simply went pop and stopped working. I am guessing a blown
component. Interestingly there appears to be a fractured leg to
that component. So I salvaged the fuse and moved onto the brick.

I have opened the brick before. Note that the screws to the heavy
500 PSU are longer and the case is consequently different. There
is no obvious reason for failure though a slight discolouration
in the fuse may point to it being blown. So I swapped the fuse
out and did what I should never like ever do... test it on a
working Amiga. Amazingly the Amiga 600 powered up and so I
thought it was job done. Sadly not.

I then screwed back the case and quite by mistake switched the
power back on at the wall forgetting the PSU was still switched
on. Fortunately the A600 wasn't connected. There was a low pitch
hum coming from the PSU. I decided to video the noise and then
suddenly the noise got louder and there was obvious smoke coming
from the PSU. So I switched off.

And so I failed and probably dealt a killer blow to any repair on
the PSU. I do tend to just leave well alone when it comes to
fails like these. Never mind. I cut the plug off it to avoid any
further problems.

You can watch the video below.

A500 PSU - Burning smell.

The Heavyweight 500 PSU

Left Lightweight - Right Heavy


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Last updated 1st January 2020

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