Monday, June 16, 2014

Amiga A1200 Restoration and Repair (Part 1)

My trusty A1200 was dusted off a few weeks ago and I got to wondering whether there was anything I could do about the colour of it.  When it rolled off the Commodore production lines some 22 years ago it was brilliant white.  Now, after long exposure to the sun (by it's previous owner) it looks more like someone smoked a whole lot of B&H over it..

After a bit of Googling it appears that the yellowing is caused by a reaction of the fire retardant chemicals in the plastic with UV rays from the sun.  The damage is permanent.

Or is it?

A chance discovery in Germany in 2008 lead to the development of Retr0bright (the 0 is deliberate) which is a general name for a variety of concoctions that aim to reduce the yellowing of vintage white or other light coloured ABS plastic.  It requires hydrogen peroxide with a suitable catalyst to effectively reverse the chemical reaction and remove the yellow from the plastic.

Fortunately, there is a ready made version of Retr0bright available for all those too lazy or too inept at chemistry to make it from scratch:

Find it in the haircare aisle in Boots at £1.69 a tub (3 for 2 as well!).  The haircare aisle is not necessarily a place regularly frequented by myself having been blessed with a less than generous share of occupied follicles but the 12% hydrogen peroxide cream is perfect for the task at hand.

All that is required is to paint this stuff over the yellow plastic, wrap it in cling film to stop it drying out and then expose it to a source of UV rays i.e. stick it in the sun for a bit.


Note the white square patch under the Amiga logo.  This was a label someone had stuck to the case which I removed soon after I bought it.

Even the keyboard was affected.  The photo does not really do a good job in showing how yellow all of these keys were.


Take three tubs of 40vol hair bleach stuff, add a few feet of cling film and some freezer bags for the keys and put them in front of an intense UV source (or put them outside on a nice sunny day) and wait for a few hours.

The results are startling.


The yellow has virtually gone.  It's not perfect but it's hugely better than it was.

White keys!  The yellow has gone!

In fact, the only real snag I had was that for the grey keys it looks like the 12% (40vol) hydrogen peroxide was a bit strong.  There is some white 'blooming' effect on the bigger keys which is impossible to remove.  Whatever.  It looks a whole lot better than it did.


Houston we have a problem...

During this process I noticed that there seemed to be something a little amiss with the A1200's motherboard.  Several of the surface mounted capacitors seemed to be leaning instead of sitting perpendicular to the board.  Several of them also had green corrosion on their solder pads which should have been shiny silver.  There is no battery in the stock A1200 that could have leaked to cause this so it could only mean one thing.  The capacitors had gone bad.

Note the green solder pads on the capacitor (marked U3 47 16V).  The components next to it also have green contacts.  Yuk!

The capacitor in the centre of this picture has lifted off its contacts, presumably because it is swelling up, ready to fail and leak its innards all over the precious motherboard.  Bad capacitors!

The only option to cure this is to completely replace ALL of the capacitors on the motherboard.  There are 18 in total with the majority being surface mounted.  Not a prospect I look forward to....

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