Newer G3 Upgrade - Missing Capacitor Values

[Phipli]

I picked up a 300MHz Newer Technology G3 upgrade (the type that goes in the CPU slot on an 8600 etc.). Unfortunately it looks like it has had a bit of a rough life and three capacitors have been knocked off.

Photos attached at the end of the post, but basically while it might just work without, for stability and piece of mind, I'd prefer to replace the missing capacitors.

The capacitors of interest are C63, C67 and C82.

Does anyone have a similar card (Same PCB, same speed ideally, but most if not all the caps will almost certainly be the same on other speeds with the same board)? If so, would someone be able to take measurements of the capacitors on their card? Alternatively, I could take the measurements myself if someone in the UK was willing to loan me a card (if your card is also missing different caps, I could use mine as reference and replace them for you ).

Realise it is a long shot, but hopefully someone can help out.

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[Fizzbinn]

I have what looks to be the same Newer Technology G3 upgrade card but at 250MHz. Your missing caps look the same as the other unmarked brown caps that are used all over this board. I think they'd need to be desoldered to measure the capacitance for sure but maybe they are "standard" decoupling capacitors all of the same value? I think I've seen 0.1uF 50V come up as the value for decoupling capacitors on RAM SIMMS, maybe same here?

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[Phipli]

I think they'd need to be desoldered to measure the capacitance

Yes, that's correct. Plus the right type of meter.

but maybe they are standard decoupling capacitors all of the same value

In this context that's unlikely - some / many will be, but not all of them. For example, see how some are a different size? That implies that they're significantly different in spec, either voltage or capacitance, to each other. Then even within a specific physical size, some will be different.

 

[Fizzbinn]

Okay, I do have an LCR meter that I think should work but it may take me a while to be able to work on this with enough free time and the right level of attention, those are some small caps! Hopefully you're not in a rush!

 

[Phipli]

Okay, I do have an LCR meter that I think should work but it may take me a while to be able to work on this with enough free time and the right level of attention, those are some small caps! Hopefully you're not in a rush!

No rush at all, if you can it would be super helpful.

 

[trag]

I suspect they all are decoupling caps. The larger ones are further from the center of the PPC chip suggesting that they are simply larger capacitances, in a larger package.

The only two things on a CPU card that might need a capacitor that isn't a bypass capacitor, I think, are the power supply circuit and maybe the timing circuit. But the clock circuit is almost always just an oscillator or crystal with a clock buffer, or sometimes an actual clock generator with a clock buffer.

Of course I could be wildly wrong.

I have a partial reel of those square cross section caps. The package won't tell you much about the capacitance, but the part number I have for that style is GRM40X7R103K100. Apparently, GRM40 is the package type in the old code nomenclature, and X7R is the series.

 

[mg.man]

No rush at all, if you can it would be super helpful.

I'll also have a look... I know I have at least one Newer Tech G3 card... but I need to locate it and see if it's the same as yours. If it is, happy to send it your way on loan to hopefully assist in getting yours going... Stay tuned.

 

[Phipli]

The larger ones are further from the center of the PPC chip suggesting that they are simply larger capacitances, in a larger package.

That's really what I was saying, my point is that they're not necessarily all the same value - I was asking for values to match what was there by design, especially as some caps around the CPU are likely tuned based on the clock frequency/trace length (although a value from a similar frequency board is going to be close enough).

I'll also have a look... I know I have at least one Newer Tech G3 card... but I need to locate it and see if it's the same as yours. If it is, happy to send it your way on loan to hopefully assist in getting yours going... Stay tuned.

Thanks @mg.man much appreciated. I should be able to return it pretty quickly - it's a 10 minute job

 

[mg.man]

Thanks @mg.man much appreciated. I should be able to return it pretty quickly - it's a 10 minute job

Well... I don't usually locate stuff that quickly, but you're in luck...

Not exactly the same as yours... but it has the same DT351 REV C board. If you want to have a go, DM me and remind me of your address...

 

[Phipli]

Well... I don't usually locate stuff that quickly, but you're in luck...
View attachment 100042
Not exactly the same as yours... but it has the same DT351 REV C board. If you want to have a go, DM me and remind me of your address...

Close enough same PCB and speed, just a slightly slower cache speed and a different solder mask colour. Thank you.

BTW, if you use the PowerLogix drivers (I basically do with any card regardless of manufacture) you can manually set the cache multiplier so you could just override the setting and your's would run the same speed as mine. If it was unreliable at all, you just set it back again (you can boot with extensions off and it won't adjust the cache speed then). Cache is King with these things, it makes quite a difference.