Maintenance : Recapping my Amiga 600's

Some time ago I bought some Amiga 600's.  Both were sold as not working.  One was actually completely fine, the seller didn't investigate it properly.  One has a memory fault which was fixed by bypassing a bit of corrosion on the board. However both of them are showing signs of leakage on the surface mount capacitors.  I've been putting it off but now I really need to do something before any real damage is done.

Firstly . . . STOP!

There are some little square metal cans on the board . . . don't get cleaning fluid / isopropyl anywhere near them . . . or you may be surface mounting a new composite video chip on your board.

More on this later.

Do your research / Buy the right tools

I've been looking at this for ages and I've watch twist methods, cut methods, solder iron wiggle methods and finally hot air rework methods.  The only one that appealed to me was the last one.  I didn't have a hot air rework station yet so I set about trying to find a good one.  I looked at the ridiculously cheap Atten right up to the Hakko, but in the end I got a Quick 861DW as recommended by Louise Rossman and later reviewed by Dave Jones.

I'm glad I did, using it made getting the SMD Caps off an absolute breeze.

Now putting back the Caps that was an issue.  Pretty much every video I watched only showed the Caps coming off.  No one actually showed them going back on.  This sort of concerned me as people showed everything up to putting the new Caps on and then bang, they were done.

I did experiment on a practice board putting on the Caps with the Quick, but I really didn't get the result I wanted ( probably due to total inexperience ).  I did however have much better success with leaded solder paste and a soldering iron. I saw this in only one video I watched, so thanks to that guy for showing the process.

Where to start?

I started with the two caps right in the middle of the board, there were no components or connectors near them and so it was a good place to get my eye in.  I held the Cap with some tweezers while I slowly move the heating element side to side.  I found I only really needed the air on about 1/3 of the maximum and kept the temp at around 250.  The Caps popped off really easily.

I did find I used too much paste for the first two.  For the next three caps near the floppy connector I used less paste and flux which made a massive difference.

You'll probably notice that I am using the solid electrolyte capacitors from Retro Bench in the photos I did look at pricing buying these myself but it ended up being cheaper to get the kits from them for just doing my two 600's.

Doing the hard bits

There were two areas of the board that I thought were going to be really hard. Between the keyboard connector and the sound jacks and the cluster under the RF modulator.

I decided to tackle the keyboard caps first, I was planning on taking the jacks off but after removing the RF modulator ( and the trouble I had with it ). I decided just to try the Kapton tape.  I removed the top of the keyboard connector first and stuck on the Kapton tape.  I then quickly used the Heat gun to remove both of the Caps.  I then soldered the Cap nearest the white jack first and then the red using a really find solder tip.  In the end it turned out great.

 I am up to the RF modulator and the cluster of caps underneath it basically made this operation really difficult without removing it.  I was going to get rid of it anyhow as I wanted to put HDMI/VGA into this Amiga 600.  I watched a video by Ms Mad Lemon who had a great tip on removing it.  Unsolder the small pins, then unsolder the big pin at the edge of the board, then wedge something underneath and slowly push the other pins through with the iron.

 

I sort of did this.  I removed the small pins solder with my desoldering gun.  I used solder wick and lots of flux to remove as much solder as I could from all of the big pins and worked hard on the big edge pin until it was clean.  Then I used a plastic spudger to help lever the modulator off while using the iron to melt and push through the remaining two pins.

Here we go with the last Caps.  Hopefully it's all working once I get them on.

So I go the new caps on and it works perfectly via RGBI.

Except . . . go read these links . . .

http://www.waveguide.se/?article=amiga-600-video-encoder-upgrade
 
https://www.ikod.se/z221-z222-fix/

https://www.ikod.se/cxa2075m/

 Take home tips

Use tweezers and a hot air rework station to remove the caps.  Not too hot and a medium airflow.

Use small amounts of leaded solder paste and flux to get a good join.
Use Kapton tape to protect plastic bits
Remove the top of the keyboard connector to get some more clearance.
Use solder wick and desoldering guns to remove solder from through hole components
Use plastic spudgers to apply leverage
Remove the RF modulator to get clearance ( chances are you'll never use it again so leave it off ).

** WARNING DO THIS REALLY CAREFULLY ** 

Use solder wick to clean the pads then give it a good clean with isopropyl alcohol.
with a small amount on a cotton bud. Clean up with isopropyl after soldering.

Keep all fluids away from the 221 and 222 metal cans or you will damage them.

If you do damage them . . . well . . . read my blog entry on fixing the Amiga Video.

 

Repair : Amiga 600 Keyboard Troubleshooting and Fix

Having never owned an Amiga before and definitely never opening one I did something silly.  I pulled the keyboard membrane right out of the socket without unlocking it.  Only once I had fixed the board and got it back to a bootable state did I realise that a whole row of keys ( the caps lock row ) was dead.

So off to the internet I went. I read a lot about people inadvertently stripping the material off of the end of the membrane or just doing it from taking their Amiga's apart a lot.  I though darn it I just broke it.  However when I looked at the end of the membrane there was heaps of material left on it, nothing like the photos I had seen.

The people were talking about bad sockets as well.  I had a second Amiga 600 so I carefully unlocked the socket and swapped it into the other Amiga.  It worked, so there was nothing wrong with the socket.

The last thing I read was about carefully checking the membrane looking for breaks.  All in all it looked fine until I got to where the tail went into the keyboard.  I had already noticed rust on the RF shield above a corroded trace.  When I looked at the keyboard tray it was rusty in the same position.
Obviously the previous owner had spilt some water in the keyboard and it leaked.  And right at the join two of the traces had completely oxidized.

 It may be a bit hard to see in this photo but under the microscope it was easy to see lines 3 and 5 (from the left) have turned to mush.  I confirmed it with a multi-meter as well.  There was no fixing this bad boy.

I headed off to EBay and after carefully checking the membrane type ( there are different A600 keyboards requiring different membranes ), I got a membrane from retrocloud-store.
https://www.ebay.com.au/usr/retrocloud-store?_trksid=p2047675.l2559

The membrane came nicely sandwiched in two thick pieces of cardboard. Now it was time to clean up the keyboard.  The keyboard was dirty, however a good going over with a blower, a damp cloth and some q-tips fixed that. The tray was another issue.  Water had gotten into the edges and had rusted the inside of the tray.  I gave it a good sanding and washed and dried it.  Then I gave it a coat of Zinc Gal (used to protect welds) over the tray.

Now I've got nice clean working keyboard to go with my Amiga 600.

Repair : Amiga 600 for parts, not working ( corroded trace )

Due to my geographic location, local population and transient demographics it is really difficult to get reasonably priced Amiga kit.  Working Amigas are like gold.  So the cheapest solution I have is unfortunately Ebay and "For parts, Not working".

So far I have bought two "For parts, not working" Amiga 600's.

Amiga 600 number 1

The first Amiga I got came all the way from the UK,  It was grubby but overall it was in good condition.  Opening the case it was clean, the caps have not leaked ( yet! ) and it looked in really good shape overall on first inspection.

Powering it up told a completely different story.  The screen flashed from grey to green.  I hit up Google and found this wonderful resource.

http://wiki.classicamiga.com/Amiga_boot_error_code_colours

Seems like I had an error in the Chip Ram.  Initially I thought I'd have to recap it first, but then I noticed a little fuzzy blue coloured dot near the RAM.

One of the traces to the RAM had corroded into a blue copper oxide puff ball.  I cleaned it with some Isocol and a cotton bud and found the trace has completely disappeared.  Using a multi-meter I tested all of the surrounding traces and found only one was broken.

A little soldering and some wire and hey presto, a fully functional Amiga 600.

Update : the other corroded trace also finally gave up so I've bypassed that one as well.  It was pretty bad before I cleaned it up.  This time I scraped all of the bad traces off of the PCB.