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I directed some AI art. The ‘bad’ trace was supposed to have 90 degree bends…

If you do remove it for cleaning, and don’t find trace issues, use a new part when you come to replace. You can get F253 chips here, pick up four: https://mou.sr/4mOnDtM Also would be sensible to pick up a couple of LS166: https://mou.sr/4lYI6uH And a couple of LS393: https://mou.sr/4mOnUNk

I borrowed the 512MB PC133 module from my iBook. It works fine on its own (but detected as 256MB of course) and also works with either my 32MB or my 64MB DIMM as long as it’s in the lower slot. (The other way round causes a kernel panic or lock up during boot.) So, am running stable with 320MB...

Wow, so weird! That’s stock.

With regards the screen issue specifically, I would tone out the connections to UD8 using the schematics - are there any broken traces? If not UD8 might be faulty - new parts are available. Could the scratchy audio be dirt/corrosion inside the headphone jack? It has a contact closure that...

A8 is pin 3 of UD8, so I think you're right on the money there.

Looking back at your earlier post, it appears it does. 66MHz bus = 3:1 ratio 83MHz bus = 2.5:1 ratio 100MHz bus = 2:1 ratio I'm not sure if this has ever been discussed before.

Just wanted to run this past the hive mind. I want to add 2x 256MB DIMMs to my iMac G3 Rev A. So, how do I identify low-density 256MB DIMMs? I assume they need 8 chips on each side, like this: Note: I do not want to use high-density 512MB modules for this even though they would technically...

I got the bus running stable at 110MHz – that's with a 36.66MHz PCI clock. To do this, I set the PCI clock generator (SC608) to its 35MHz setting and swapped its reference crystal for a 15MHz part in place of the stock 14.31818MHz part.

The solder joints on these chips look damaged, certainly due to electrolyte from the old cap at C7: The picture you’re seeing looks like part of the VRAM is not getting written to (default state showing through), likely an addressing error. So start with repairing the joints on the F253 chip...

It sounds like an aircraft taking off, and that’s at 7V. At 12V it’s like a hurricane. I’m hoping it’s just having issues with those particular 512MB DIMMs you have, and not that 256MB total is a hard limit. Can you try some different large (>128MB) DIMMs? It’s irritating, isn’t it...

Yes. I bumped PCI to 35MHz for a 105MHz bus speed. It runs but there are problems with USB.

That’s kind of what I suspected. It’s not an issue with a particular slot, but with driving 2x DIMMs at 100MHz. The XPC106 and the MPC932 are both operating within design spec so I wonder if the issue is something like non-optimal PCB routing causing jitter or signal loss. I doubt if Apple ever...

I’ve never seen a 750P - is it the same as a 750L?

So you've tried the 128mb and 512mb modules in the top slot only (with nothing in the lower one), and it doesn't boot?

Sure, let's talk. Send me a DM. If you're just looking to upgrade the XPC106 chip for 100MHz bus operation and keep the CPU, then a Rev. D daughterboard would be better, since I don't think multipliers lower than 3.5x are possible. So you could potentially leave the CPU on there and run it at...

That’s a great result! Well done! Especially interesting about the L2 ratio. I’m going to pick a couple of 256MB SO-DIMMs and see if I can get it to boot.

Yes - it’s exceedingly unlikely to be a brand new capacitor that’s causing the issue unless they installed it backwards :P I’m working on an 840AV board right now that has no video and no sound (except for the startup chime). The original caps ravage these boards so it’s generally corroded...

It’s the only PowerPC Duo that was ever made, so it’s pretty desirable and interesting. It’s a 100MHz 603e on a 32-bit data bus with no L2 cache just like the PowerBook 5300 series, so it’s not likely to be the best computing experience. Enjoy it and be patient with it. The ImageWriter II...

It might be dirty contacts inside the headphone jack. When you remove the headphones, it closes a contact that routes the audio to the onboard speaker, and these often get dirty or corroded with age. Then you get issues like you’re having. - try spraying contact cleaner into the jack - try...