I picked up a Power Macintosh 7100/80 AV with the AV video in/out card a few months ago. Last night I decided to tackle this behemoth. The logic board has 25x 47uf 16v caps, and one 100uf 6v cap. The video card has 13x 47uf 16v caps.

Overall not a bad nights work but quite overwhelming if you aren't experienced in this work.
All of the caps are the bigger size so it's not like soldering down those rice size caps as you find on an LC.

These logic boards have a different solder mask coating than many other Macs, and it's similar to my Quadra 800 boards and many 6100/66 boards. It seems to clean up nicely and I did not notice any signs of trace corrosion from leaking caps.

The pads under each cap had a dry residue from leaking caps. I plan to attach some heat sinks to a lot of the chips to avoid any overheating.

You've probably already done it, but don't forget to replace the heat sink compound on the PPC601. Still smarting over the hours I spent trouble-shooting 20 years ago, when the whole problem was bad heat sink compound....

>> trag said:

You've probably already done it, but don't forget to replace the heat sink compound on the PPC601. Still smarting over the hours I spent trouble-shooting 20 years ago, when the whole problem was bad heat sink compound.... Click to expand...

Actually, I hadn't done it yet. Is the heat sink hard to take off and put back on?

It should just be four clips through the motherboard holding it on.

Be gentle and exercise care though. You do not want apply much downward pressure on the CPU. They're prone to cracking.

Also, do not over-apply the replacement heat sink compound. It's just filling the un-flat places between the apparently flat heat sink and the apparently flat tiny CPU die in the center of the big CPU package.

I overapplied the first time I did this (on a Power120) and heat sink compound ran onto the pins of the CPU causing shorts.

I've not yet recapped any of my early PPC systems, interesting to hear you found evidence of leakage on yours!

And wow, 38 caps total!

>> Garth Beagle said:

I've not yet recapped any of my early PPC systems, interesting to hear you found evidence of leakage on yours! And wow, 38 caps total! Click to expand...

I bought a beige G3 logic board in April. It didn't want to work right. I recapped it, and it worked great after. There was the beginnings of cap leakage residue under some as well.

I recapped another beige G3 board for someone recently, and it had cap leak juice (still a liquid I could touch) under the caps.

So it's definitely becoming a problem. I say generally anything 20 years old and older needs to be done soon.

Well, good? Good to know of course!

>> Mr. Fahrenheit said:

I bought a beige G3 logic board in April. It didn't want to work right. I recapped it, and it worked great after. There was the beginnings of cap leakage residue under some as well. I recapped another beige G3 board for someone recently, and it had cap leak juice (still a liquid I could touch) under the caps. Click to expand...

Ah, good to know. I haven't done anything with my problem Beige G3, but these anecdotes all support the liklihood that the problem is age/cap related.

I just got a 7100/66 board in the post - each and every electrolytic cap has leaked and leaked into the ground plane surrounding them! :eek:

>> Kai Robinson said:

I just got a 7100/66 board in the post - each and every electrolytic cap has leaked and leaked into the ground plane surrounding them! Click to expand...

Gah! If you can, post a photo

Saveable?

Wow, I have never seen black cap juice like that! I don't think I've ever seen a gold Mac Logic board either. I wonder which other models have them. The only other color I've seen are the blue iLamp boards.

That's not even the electrolyte, that's the solder mask that's become black because of the electrolyte, it's seeped underneath and eaten it from beneath.

>> Mr. Fahrenheit said:

I picked up a Power Macintosh 7100/80 AV with the AV video in/out card a few months ago. Last night I decided to tackle this behemoth. The logic board has 25x 47uf 16v caps, and one 100uf 6v cap. The video card has 13x 47uf 16v caps. Overall not a bad nights work but quite overwhelming if you aren't experienced in this work. All of the caps are the bigger size so it's not like soldering down those rice size caps as you find on an LC. These logic boards have a different solder mask coating than many other Macs, and it's similar to my Quadra 800 boards and many 6100/66 boards. It seems to clean up nicely and I did not notice any signs of trace corrosion from leaking caps. The pads under each cap had a dry residue from leaking caps. I plan to attach some heat sinks to a lot of the chips to avoid any overheating. View attachment 93 Click to expand...

I have a friend who would like me to recap one of these for him. It looks like C62 is the 100uf cap, is that a 6v or 6.3v? Just trying to have the correct parts ready for when I get his board. Nice post and good pictures as well.

You can use 100 uF/10V which is pretty commonly available and removes the uncertainty about 6V vs. 6.3V.

Thanks trag, I appreciate it.

Thank you for this. I just recapped the very same machine and it was my first recap. Now I'm facing a broken adb port :(. Mine hasn't got the metal at the back and just has white plastic hmm.

>> Initialise_Disk said:

Thank you for this. I just recapped the very same machine and it was my first recap. Now I'm facing a broken adb port . Mine hasn't got the metal at the back and just has white plastic hmm. Click to expand...

There's a thread around here somewhere all about how to find various connectors. Lists part numbers and sources for things like CPU slots and power connectors. I think Phoenix Enterprises has the ADB port, IIRC.

https://www.peconnectors.com/audio-dc-power-mini-din/hws3276/

>> trag said:

There's a thread around here somewhere all about how to find various connectors. Lists part numbers and sources for things like CPU slots and power connectors. I think Phoenix Enterprises has the ADB port, IIRC. https://www.peconnectors.com/audio-dc-power-mini-din/hws3276/ Click to expand...

Thank you! I just need to figure out how to remove the port. It's really hard to desolder them.

Mouser also sell 4-pin mini din sockets that fit perfectly.