Welcome to the fun world of leaking electrolytic capacitors. Trace damage like this is very common and if someone replaces the capacitors without properly mitigating the damage the corrosion will continue to spread and get worse. 'Half-way' repairs cause as many problems as the original failures.
Cleaning with the fiberglass pen to get the loose/flakey stuff off and down to bare copper is essential. The electrolyte is acidic so you can use a mild alkaline solution to neutralize it, something like baking soda and water, or Formula 409 (any alkaline home cleaning product would probably work). Let that set on the corrosion for an hour or so and then wipe off and flush with alcohol. Once the alcohol is dry apply paste flux and tin up all the bare copper. This will not only help protect the copper it will also bring up more contamination. Then clean again with alcohol. This is a good time to ohm out all your traces and plan how to do any trace repair. Once that is done, or done as much as you can before reinstalling the caps coat the al; the tined areas, except where you will solder, with a PCB topcoat or nail polish. Let that dry and then install your caps and add any needed bodge wires. This is not hard work but it sure is time consuming. Jeff Birt -----Original Message----- From: M100 <m100-boun...@lists.bitchin100.com> On Behalf Of Eric LK Sent: Sunday, April 11, 2021 7:17 AM To: m100@lists.bitchin100.com Subject: Re: [M100] Need help fixing VEE on M100 Le lun. 22 mars 2021 à 19:05, Eric LK <tr...@lefauve.org> a écrit : > > I didn't recapped this unit because the seller I purchased it from > told me he did it a couple of years ago, but I think I'll just follow > your advice on this (also, I'm not sure he did clean the flux). > > I already have the caps so I guess I know what I'll do next week-end > :o) I eventually freed some time to look into recapping this unit, but I kind of stop in the middle to ask for some advice: Looking at the PCB, I could confirm that the unit has been recapped recently as the previous owner said, so I tried to first change only the caps near the power supply (C82, C83, C84 C85, C86, C90 and C92). I tested all of them, and they appear to be in specs, so I had a good look at the PCB under the caps I removed, and I think that may be the problem... I put some pictures on http://pics.lefauve.org/Recap2021/ (that were taken after using IPA, an "electronic cleaning solvent", more IPA and a glass fiber pen; it was looking worse before...). I'm a little concerned about some of the caps pads and their connecting traces like C82, C85 and C86. I've never come across this kind of damage before and I'm not sure how to continue. My first thought would be to replace the caps, and to use the schematics to check the continuity between each of those cap legs and whatever they're supposed to be connected to, bridging any non-conductive trace with some wire but I could really use any advice you have before risking to make everything worse :o) Eric.
