PcW16 Service Manual?

[pollito]

Hi all,

I recently bought a PcW16, which is working fine, however there is a lot of corrosion on the board which has spread to the ports closest to the battery.

I want to remove the battery as soon as possible, and clean off the corrosion. But opening the machine, I can't work out what I need to remove to access the mainboard (which is underneath the CRT PCB, and is screwed into the case). There are wires soldered from the CRT to its own PCB, but I can't really see if there are any soldered between that board and the mainboard, or how it is connected. I am guessing I will need to remove the CRT first, and am moderately scared of CRTs, so am being ultra cautious.

Does anyone have the service manual for this machine? I checked on @JohnElliott 's site, but couldn't find anything. Or, perhaps someone else has done this before, and wouldn't mind guiding me?

Thanks in advance for any suggestions.

[Bryce]

Hi,
   can you post a picture of the corrosion on the mainboard? Your description unfortunately sounds like a write-off. If the battery has leaked that far across the board, it may not be repairable. There will be corrosion into the via's and the inner layers of the PCB that would be impossible to correct and with no way to remove the acid and stop the process.
When you take the PCB out, hold it up to a very bright light and the extent of the corrosion will show up as a shadow. But there will be more than one shadow, that's the corrosion inside the PCB. Then you can judge for yourself how big the issue is.

Bryce.

[pollito]

@Bryce thank you for your reply, and for your advice. Sure, here are some pictures. I can't work out how to upload them to the forum, so I have put them on my server:







I admit that it doesn't look good, and I have never seen this spread to a port before. But, on the plus side, the machine works fine other than the RTC, and the damage looks like it's in a reasonably unpopulated part of the board, so maybe all isn't lost?

Are you sure this battery would have acid in it and not something alkaline-based? I know the goal is to neutralise the gunk, so bicarbonate of soda for acid, or vinegar for alkaline, but I can't yet see any markings on the battery from this angle to search for the part number.

[pollito]

@Bryce I have made quite a bit of progress. The majority of the damage was to the solder mask. The only tracks that were damaged were the ones underneath the positive terminal, which I have now repaired. Other than that, I only needed to replace a couple of passives, as well as the printer, serial and mouse ports.

All that is left is to solder the speaker back on, fix the mess I made of the RF shield when I tried to remove the rust, reconnect and reassemble.

I am considering replacing the rest of the electrolytical caps. I bought some fancy low ESR ones, because I read that they generate less heat, and therefore last longer (I never want to open this thing up again!). Do you know if fitting low ESR caps would be okay, or if it might cause issues? Would you replace the caps while you were there, even if they looked fine?

Here are a couple of pictures. It's not going to win any beauty awards, but I'm hoping it will keep the computer working for another 30 years :