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ScuzzBlog: Diaries December 2017

Entry 28th December 2017: Post: 1

The last A500

I guess I have over 35 Amiga 500s in various guises. From 500s to
500 Plus' and contained within other machines. Of all the Amiga
500 variants I have only one that doesn't work. They are a hardy
breed of Amiga and so it is of particular importance to me that
I get this last Amiga 500Plus working.

And so we venture forth to save the last of my 500s

So here is the problem

Graphical issue on screen as seen

So I set too checking the chips, damage
and continuity of the circuits

The floppy is working and there
is power to the main circuits
Keyboard and mouse are working

The battery was removed from the board
a good while ago now.

My first port of call is with Denise

I have already swapped out Paula

Shows why you should use the
IC Puller to remove chips.

I checked thoroughly all tracks
and they are all fine

Enter a busted motherboard of unknown
origin. No idea where it came from. All
I know is that it was busted when I got it

I checked traces all over this
board for continuity and all I
could find was a lack of activity
to the far end of the CPU and a
dodgy capacitor/resistor.

I swapped over the Denise but
made absolutely no difference

Next stop and the fat lady

I will remove the Agnus from the
busted motherboard. I don't have a
PLCC extractor so fingers crossed there
are some big holes in the board
First though remove all the port screws

Man is this board rusty at the.
port plate. Looks like it was left
in a wet location. Probably loft
or outside shed / garage. Looks like
water actually got into the machine

Exposes the battery damage on the
doner board from below

Looks a lot worse than it actually is

Sadly the Agnus chip does not
have any holes in the board to
aid extraction so I will have to
acquire the correct tool to remove

More damage to the busted motherboard

Corrosion seeping through here

There are white tide marks next to the chip

Looks too much for a capacitor. I am
guessing water ingress. Could be wrong

Whilst here I checked for continuity

All the traces were working fine

OK so I have to press pause as I wait
for the extractor. I could use a small
screwdriver, but in truth I would likely
break the socket and they are a pig to
repair. Just not worth the risk

The Agnus has some strange green discolouration
to the one side which I cannot explain

Fingers crossed its nothing to do with
U40 or U41 cus that exposes me to an
Indiana Jones fear of snakes.... !!

More to follow soon

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Last updated 28/12/2017

Chandraise Kingdom

Keep the Faith
scuzzscink 2017