Beige G3 Desktop Restoration

[displaced]

Hi!

I picked up the filthiest G3 Desktop from eBay. Stripped it down and did a cleanup of the battery corrosion, replacing it with a CR2032 coin cell.

With the logic board on the bench, connected to an ATX PSU (with the PSU Type jumper set appropriately) and with the speaker and Whisper PERCH board installed, I head the startup chime!

However, it’s not quite right still. Sometimes it’ll refuse to power on. Sometimes the PSU will stop and start a few times before the chime. Currently, I’m struggling to get it to start at all.

Unpredictable startups makes me suspicious of the SMT capacitors, so I’m planning to do a recap of the board.

So, a couple of questions: does that sound like a reasonable plan of attack? And also, I’m struggling to find a schematic for the Gossamer logic board. Does anyone know of one online? Oh, and I know the machine’s a bit too obscure for anyone to have bothered putting together a recap kit, but does anyone happen to have a list of caps on the board? I have a couple of caps whose labels are illegible. I may well be back here asking if anyone has a Gossamer, and would they mind checking the cap specs at a few positions, if that’s okay!

Thanks for your help!

Chris

(edit to add: I’ve no idea what, if anything is on the display — I’m still waiting for Mac-to-VGA adapter! Anyway — once I’ve got it starting reliably, I can at least get the scope on the video signals to see if they appear okay, even if I don’t have the adapter yet!)

 

[3lectr1c]

Pics of the board? How bad was the battery damage?

also, if you or someone can get the cap values, I’ll add them to the cap reference database on my website for future use.

 

[displaced]

Here’s before and after. Cleaned up really well with white vinegar and a distilled water rinse.

I’ll start putting together the cap list — at least the ones I can read!

(edit: the underside was pretty much untouched — cleaned up fine with some IPA only. But, I admit I’ve not checked incredibly closely for bad traces — I didn’t worry as the machine was starting up (mostly) fine)

 

[3lectr1c]

It's worth noting that I've heard the CPU VRM modules in these can need to be recapped, or that some are just crap in general. You might want to go there next, I'd suspect those over the SMDs on the board at this point in their life. It's never a bad idea to replace them though, I recapped my perfectly working PB 3400c (1997) just because.

 

[displaced]

I read the same! Apparently the VRM boards marked ‘Royal’ are the bad ones — which mine isn’t — but it’s still a good first place to look. Thanks for the reminder!

 

[displaced]

Whilst I’m waiting for the VRM board caps, I’ve been having a fiddle.

The machine was in a state where it did absolutely nothing when power was applied.

I noticed a bit of gunk at the top left of the board, near the PSU Type jumper, so I gave it a spray with some IPA to start cleaning. To my surprise, the PSU fan started whirring — I’d accidentally left the switch on!

Now, the machine still wasn’t starting. The fan on the PSU would repeatedly spin up, and the power LED was dim.

I turned it off, finished my cleaning, and on a hunch got my multimeter on the PSU Type jumper pins.

I was getting continuity on the MAC side, even with no jumper! So I gave that a thorough clean and now I only get continuity on the pins which are jumpered — the ATX pair for me.

Now the PSU fan spins normally and the power LED appears to be full brightness. But still, the machine no longer chimes. Ugh. I hope something hasn’t popped!

Oh — a quick question: is it safe to apply a bit of thermal paste on the CPU? Just an idle thought, as it’s something I’d usually do, but the G3 doesn’t have the usual metal ‘lid’, so I thought I’d better check.

 

[3lectr1c]

Applying thermal paste to a bare CPU die is completely safe. The "metal lid" you're talking about is called a heat spreader, and it's job is to act like a tiny integrated heat sink to spread the heat out more for the cooler (pretty sure that's the purpose anyway), and I do believe there is thermal compound between the die and the heat spreader on chips that have one.

Integrated heat spreaders have only really been a thing since the Pentium 4 era, although many earlier chips covered up the bare die by other means (think 68040), although I believe AMD K6 chips have something similar to a heat spreader. Most if not all laptop chips still don't use them either, my laptop's CPU and GPU chips are the bare die only.

 

[displaced]

Excellent — I shall bear that in mind should this machine ever start up reliably!

 

[displaced]

I ended up getting a second machine from eBay and combining the two to get a functioning machine.

Without schematics, I lack the skills to trace the fault on the original logic board. But now that I’ve got a working board, I might be able to compare and contrast to find where the issue is. Maybe!

So anyway, the new machine has a less-rusty case, so I used the new case and logic board with all the other parts that I could restore fully from the original machine making up the rest — so I have one fully-functional G3 Desktop and one collection of bits that one day might make a working-but-ugly second G3 Desktop.

Been interesting to compare a rev.1 with a rev.3 board. Plus, the ‘Whisper’ PERCH cards are quite different too, even though they’re interchangeable.

 

[3lectr1c]

Ah, the best solution to fixing a computer that won’t boot. Get another one!

 

[displaced]

Hah! Indeed

I’ve not given up hope for the other logic board. I’d love to get it working again, and the chances are better now that I have a known-good machine to compare.

I dare say that someone with better skills would have it up and running in no time. But I’m treating this as a learning opportunity

 

[3lectr1c]

Good luck!

 

[Patrick]

I ended up getting a second machine from eBay

This might come from a place of privilege. but i really like having multiple computers of the same model. That way i can swap parts between to figure out what exactly is broken. .. or in the case of a battery bomb know what parts were rusted away.