Amiga 4000 battery repair - advice needed!

[PacificState]

I have an Amiga 4000 here that won't boot, and so the first thing to look at is obviously the battery.

The battery wasn't actually in bad shape, although it appeared to have already been replaced. There's still something off, though - having desoldered it, there appear to be some greenish chip legs (see U177), as well as some slightly blackened traces and a via with an odd tint.

Having let the board soak in vinegar before cleanup with IPA, I'm inclined to replace U177, then scrape off the blackened mask and solder over it. Does that seem reasonable? I'm a bit surprised that the traces and IC look suspicious without more evidence of a leak...

[mortenkjerulff]

Originally Posted by PacificState

I have an Amiga 4000 here that won't boot, and so the first thing to look at is obviously the battery.

The battery wasn't actually in bad shape, although it appeared to have already been replaced. There's still something off, though - having desoldered it, there appear to be some greenish chip legs (see U177), as well as some slightly blackened traces and a via with an odd tint.

Having let the board soak in vinegar before cleanup with IPA, I'm inclined to replace U177, then scrape off the blackened mask and solder over it. Does that seem reasonable? I'm a bit surprised that the traces and IC look suspicious without more evidence of a leak...

Hi PacificState.

With my very limited experience, I would desolder U177 and clean the pcb underneath.
I would also scrape off the blackened soldermask and clean the trace underneath.

Have you recapped the board?

Cheers
Morten

[jbenam]

Hi there,

Desoldering U177 and cleaning underneath the IC is definitely recommended. Before scraping and resoldering traces I would test the trace with a multimeter in Ohm (resistance) mode. If you get near 0 Ohm, the traces should still be ok and won't need to be scraped (the top layer is just lacquer).

[PacificState]

I removed U177 with ChipQuick, then scrubbed the PCB and traces with vinegar followed by IPA - and it boots! While blackened solder mask came off with the scrubbing, the traces seem fine - so a new IC and a conformal overcoat pen should get things into shape. Thanks all!

[amiman99]

Another A4000 saved! Nice!

[mortenkjerulff]

Congratulations :-)

[Turran]

Originally Posted by PacificState

I removed U177 with ChipQuick, then scrubbed the PCB and traces with vinegar followed by IPA - and it boots! While blackened solder mask came off with the scrubbing, the traces seem fine - so a new IC and a conformal overcoat pen should get things into shape. Thanks all!

If you've taken of the top layer, you can also tin the traces while you're at it. It adds an extra layer of protection on them.
Just add a little bit of tin to your soldering iron and drag it over them. Not much. Can also use solder braid to spread a very thin layer of solder over them.

[PacificState]

Thanks all - the chip was replaced, the traces re-tinned, and a new replaceable battery from AmigaKit installed.

One mistake I made after this was to swap the Kickstart ROMs out for diag ROMs immediately after the repair. This left the machine unbootable - but after some consternation, I noticed that the DIP sockets were not in good shape, with bent pins. I'd been careful, too, using an extraction tool.

After bending the pins back in place with tweezers and scrubbing them with IPA, the machine is now booting again. One further problem I then faced (maybe there are more!) was that the floppy drive was stuck on permanently - but closer inspection revealed yet more bent pins on the floppy. After putting these back in place, the drive light is off and the click is back.

Next up is a recap of both the main board and the A3640...