A600 Cat and Mouse.

I was playing cat and mouse with an A600 where the mouse was quite jittery and the left button seemed to be unreliable. If the plug was wiggled and held in a certain position and if I held my tongue right, I could get it to work as long as I didn’t breathe. Of course I tried different mice and some of them were worse. Strange! I noticed some of the pins were very loose and sitting in further than the rest.

There was another problem with this machine where the power socket seemed a bit wobbly. Time to tear this one down and to crack out the soldering iron. I removed the motherboard and closely inspected the solder connections. The power socket connections were obviously broken so I re-flowed them but the mouse connections seemed fine and I re-flowed them anyway. After plugging in and testing, I experienced the same mouse issues. The re-flow job seemed to have had no affect on the wobbly pins so I figured they were broken in the socket internally.

De-soldered mouse socket

I checked the dimensions of a DB9 serial socket from a PC and it was very close, if not identical apart from the colour of the plastic molding. I de-soldered it to use as a replacement and de-soldered the faulty on from the A600. Soldered in the replacement and it tested perfectly. Problem solved – it seemed.

When I was plugging in the mouse to test while the machine had it’s clothes off, I noticed near the back of the mouse socket a missing solder pad and it’s mate was bare. I figured there was a component missing and just below it was a similar set of pads with a 4.7ohm surface mount resistor attached. It’s been around three weeks since I picked up these computers and at the time I remember seeing a loose surface mount resistor and thinking I must put that aside, just in case I find where it came from. I grabbed it and it matched the resistor nearby and it also had a solder pad attached to one side. After sitting it in position and lining things up it became apparent this was the matching resistor! I’m glad I put that aside. After measuring it and confirming it was 4.7ohms got to replacing it. The left pad and it’s trace were intact. I soldered a fine piece of wire from under the right pad to the terminal where the trace led.

Then I soldered the resistor into place.

While I had the machine apart I took the opportunity to clean the case and keyboard. Then assembled it with its hard drive, floppy drive and extra 1Mb RAM module.

After assembling I gave it a good testing and all is fine so far. I did notice while I had it apart there are a few dodgy looking capacitors. Also a couple of areas that may have been affected by leaking electrolyte but it’s very minor at this stage. It’s on my to do list to sort these issues out.

One thought on “A600 Cat and Mouse.

  • November 12, 2016 at 6:00 am
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    Looks great, Gary! I always marvel at how compact and "cute" the 600 looks compared with the 500 and 1200.

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