English Amiga Board - View Single Post - A600 Caps lock led stuck on at boot solution

PeteJ · 06 September 2014, 23:40

I went ahead and recapped the A600 motherboard today (recap thread: http://eab.abime.net/showthread.php?p=973895#post973895)

The problem with the colour output is still there however

The output is all tinted in purple and there is ghosting. It's the same through RGB scart and composite outputs.

There were four caps that I didn't replace because there was not enough clearance for soldering so I would have needed the parts in the way to be removed first which I really didn't want to risk doing: C334, C324 (near the keyboard connector) and C821, C822 (near the power connector).

I'm not experienced or qualified to know whether it's one of the tiny surface mouted resistors somewhere on the board that are at fault or if the cause is a faulty video dac chip. I only have a very basic multimeter which I've never used before so I will have to learn how to use that before I do something wrong with it and cause some further damage.

One thing I did notice was that after I removed the old caps and when I was cleaning off my flux and general mess from the areas were I'd worked with IPA, I noticed under the three caps C235,C236,C239 (which were all 100uf 6v incidentally) there seemed to be what looked like possible corrosion of the tracks in some small areas. It looked like the tracks had black patches here and there. Cleaning it thouroughly there with IPA and cotton buds didn't change it at all but when holding it up to the light I could still see the raised trace continuing in those spots so I reluctantly went ahead and put all the new capacitors in regardless.

Here's a photo showing the tracks in that area (circled in red) before I put the new caps in:

Maybe that is the cause? Does anyone know from the circuit diagram what those parts of the circuit are for and whether it will be causing the symptoms that are occuring? or, if anyone can shed some light on which other componets to test if that is nothing to do with it.

thanks very much.

06 September 2014, 23:40	#18
PeteJ Registered User Join Date: Jul 2014 Location: Cheshire Posts: 66	I went ahead and recapped the A600 motherboard today (recap thread: http://eab.abime.net/showthread.php?p=973895#post973895) The problem with the colour output is still there however The output is all tinted in purple and there is ghosting. It's the same through RGB scart and composite outputs. There were four caps that I didn't replace because there was not enough clearance for soldering so I would have needed the parts in the way to be removed first which I really didn't want to risk doing: C334, C324 (near the keyboard connector) and C821, C822 (near the power connector). I'm not experienced or qualified to know whether it's one of the tiny surface mouted resistors somewhere on the board that are at fault or if the cause is a faulty video dac chip. I only have a very basic multimeter which I've never used before so I will have to learn how to use that before I do something wrong with it and cause some further damage. One thing I did notice was that after I removed the old caps and when I was cleaning off my flux and general mess from the areas were I'd worked with IPA, I noticed under the three caps C235,C236,C239 (which were all 100uf 6v incidentally) there seemed to be what looked like possible corrosion of the tracks in some small areas. It looked like the tracks had black patches here and there. Cleaning it thouroughly there with IPA and cotton buds didn't change it at all but when holding it up to the light I could still see the raised trace continuing in those spots so I reluctantly went ahead and put all the new capacitors in regardless. Here's a photo showing the tracks in that area (circled in red) before I put the new caps in: Maybe that is the cause? Does anyone know from the circuit diagram what those parts of the circuit are for and whether it will be causing the symptoms that are occuring? or, if anyone can shed some light on which other componets to test if that is nothing to do with it. thanks very much.