Beige PowerMac G3 Capacitor Replacement

[shadedream]

My Beige G3 tower started having problems recently, so I figured a re-cap was in order. I didn't find any guide or capacitor list so I decided to make my own for reference as I worked.



Here is a capacitor list for the board and the capacitors I used (I haven't done the tiny 10uf 16v yet because I need a smaller iron tip than my normal chisel tip). They're all a slightly smaller package than I've normally used on older systems because there are more small components around the ones on this board.

16 - 47uf 16v https://www.mouser.com/ProductDetail/581-TAJC476K016SNJ
5 - 100uf 6.3v https://www.mouser.com/ProductDetail/581-TAJC107K006R
1 - 10uf 16v https://www.mouser.com/ProductDetail/74-595D106X9016B2T

One of the 100uf 6.3v capacitors is on the personality card (the case on both my basic one and video in/out one), but double check to see if yours has it as well.

Additionally, the voltage regulator board has four tall through hole electrolytic capacitors:

4 - 1500uf 6.3v

I haven't done my voltage regulator yet, but I have polymer capacitors on order that should work and will update when I get them and test them.

 

[3lectr1cPPC]

Excellent work! I’ll go ahead and add these values to my website if you don’t mind. Could I use your images there as well (with credit)?

 

[shadedream]

Go for it. More places are better for them living on long term. I'll probably get them up on mine as well once I eventually get an actual site up...

 

[3lectr1cPPC]

Thanks! I appreciate it.
Just an FYI as well, the boards between the tower, desktop, and AIO G3s are the same.

Mind as well posting a photo of the VRM board? There were multiple vendors so it would be good to know which this was.

 

[shadedream]

Yeah I bought caps to do my AIO as well. Photo of the voltage regulator doesn't really matter, they're all the same core design and same four caps (at least all of them I have) even if they're different make and slightly different layout.

 

[3lectr1cPPC]

Still would be nice to have the photo for cap reference sake.
Good to know though that they are all essentially the same though.

 

[croissantking]

This is an interesting thread, because few people on here talk about recapping their Beige G3s or deem it necessary. Had any of your caps leaked?

 

[Phipli]

This is an interesting thread, because few people on here talk about recapping their Beige G3s or deem it necessary. Had any of your caps leaked?

I've heard of it before, also 9600s, B&W and G4s. The big difference is how they fail - these just stop working, rather than the 68k corrosive self destruct. So far.

Its all moving goalposts. I have a number of Beige G3s and the caps are still ok on all of them. I recapped one that didn't work, but it didn't fix it.

There is no real need to do it preemptively, but if a machine fails, it is something to consider.

 

[croissantking]

For the VRM, I would suggest specifying low impedance electrolytics, e.g. these:

https://www.mouser.co.uk/ProductDetail/Nichicon/UHW1C152MPD?qs=Ajmft%252BTTukE9h8qJki4UvQ%3D%3D

 

[shadedream]

This is an interesting thread, because few people on here talk about recapping their Beige G3s or deem it necessary. Had any of your caps leaked?

There was some leaking underneath a few of the caps, nothing crazy bad that was leaking out onto the board around it yet though. It did have some odd behaviors occasionally before and stopped working after I added the SATA card (probably pushed something over it's limit). It definitely seemed like it was a good timing for it.

 

[shadedream]

For the VRM, I would suggest specifying low impedance electrolytics, e.g. these:

https://www.mouser.co.uk/ProductDetail/Nichicon/UHW1C152MPD?qs=Ajmft%252BTTukE9h8qJki4UvQ%3D%3D

Yep, I was chatting about it on discord. I looked up the specifications of the Nichicons on one of mine and they were a low impedance model which Mouser still sells (UPW series). They probably aren't in need of a recap, but I'll find out when I remove them and figured I'd do them since I did the rest of the boards anyway.

As a replacement I ordered some solid polymer capacitors instead that, after some conversing with people more knowledgeable than I, should work.

https://www.mouser.com/ProductDetail/710-870235175008

They should be here today, but I may not get to doing one of the voltage regulators until this weekend.

 

[croissantking]

Yep, I was chatting about it on discord. I looked up the specifications of the Nichicons on one of mine and they were a low impedance model which Mouser still sells (UPW series). They probably aren't in need of a recap, but I'll find out when I remove them and figured I'd do them since I did the rest of the boards anyway.

As a replacement I ordered some solid polymer capacitors instead that, after some conversing with people more knowledgeable than I, should work.

https://www.mouser.com/ProductDetail/710-870235175008

They should be here today, but I may not get to doing one of the voltage regulators until this weekend.

These are only 6.3V though?

 

[shadedream]

These are only 6.3V though?

That's correct. I see now that I mis-labeled them in the original post. They should be 1500uf 6.3v. I'll see if I can get an admin to edit the post.

 

[shadedream]

Ok I finally got around to replacing the last small capacitor and the caps on the voltage regulator board tonight. I will note that small 10uf 16v cap is tiny. Might be able to use a slightly larger on to make it a little easier.

The solid polymer caps are working great in the system so far. That said, the old caps did not show any signs of leakage, so it's unlikely this is really necessary yet. They were also a pain in the butt to remove and clear the vias because each leg is essentially tied to a big ground plane, one on either side of the board, at least with the module I did. I ended up using hot air to remove them and reinstall the new ones because I couldn't get the vias clear.

 

[JohnnyPhantom]

Hey there, I have the same board in my server machine, I'm doing a cap replacement on it as well. What were the issues your machine was having leading you to replace the caps? Have they been resolved since? I also have 1 more issue I'm hoping you can help me with (as posted here https://68kmla.org/bb/index.php?thr...mponents-on-the-logic-board-820-0991-b.45951/ ) any chance you could tell me the values of C241 and R151, I think mine have been damaged by the battery.

 

[shadedream]

I was having issues with it refusing to boot after I added a third expansion card. Caps may not necessarily have been the issue since CUDA is so finicky on these machines sometimes, but everything is working fine since the re-cap and fighting CUDA. No idea on the values of the cap and resistor, I don't have the means to measure them inline.

 

[JohnnyPhantom]

I was having issues with it refusing to boot after I added a third expansion card. Caps may not necessarily have been the issue since CUDA is so finicky on these machines sometimes, but everything is working fine since the re-cap and fighting CUDA. No idea on the values of the cap and resistor, I don't have the means to measure them inline.

When you say refusing to boot. Do you mean ?/folder on boot. Or something like it powers on when power is pressed, fans spin, but no tone and no video? (That’s what I’m experiencing) or something else?

 

[shadedream]

When you say refusing to boot. Do you mean ?/folder on boot. Or something like it powers on when power is pressed, fans spin, but no tone and no video? (That’s what I’m experiencing) or something else?

It's been a bit now and my memory is terrible... but I _think_ it was booting to a solid screen and not going any further...

 

[mmic1101y]

I've been spending some time in Service Source lately and reading up before I start doing work, so this was fresh in my mind. Have you looked at the power draw on your cards? There appears to be a power budget on the PCI bus. From page 5:
"
Accepts three PCI cards (6.88" or 12.283"), or three 15 W cards, or two 25 W cards
"
Could be nothing, but might be worth a look?

And thank you to the wider group for dissuading me (or cautioning me) on the use of tantalum caps. I intended to resort to them but will rethink in favor of polymer.