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L2 G3 Sonnet Crescendo / ATI RAGE128 compatibility issue?

Phipli

Well-known member
Does the Sonnet CPU pull 3.3v? My thinking is both devices drawing on 3.3v would almost certainly sink it.
They tend to have onboard regulators and I'd expect that to be fed from 5V. 5V had much more capacity than 3.3V on beige macs.
 

Jaek_3

Well-known member
They tend to have onboard regulators and I'd expect that to be fed from 5V. 5V had much more capacity than 3.3V on beige macs.
That would explain why the Sonnet card doesn't ever crash the computer, but the ATI card always does under load.

I was wondering if anyone could link a better/more suitable 3.3v regulator for me to replace the current one with? I'm not good with electronics...
 

Phipli

Well-known member
That would explain why the Sonnet card doesn't ever crash the computer, but the ATI card always does under load.

I was wondering if anyone could link a better/more suitable 3.3v regulator for me to replace the current one with? I'm not good with electronics...
Its just a thought at the moment, it might not be the issue - can you connect some wires to the 3.3v and ground, run them outside the case and monitor it while under load with a multi meter? See if it dips? If it does, a higher power regulator might be needed. But I happen to have a 6500 PSU on the floor in front of me and the 3.3V is 10A!

The 6500 is a sister product to the 5500.

IMG_20220914_232024.jpg
 

Skate323k137

Well-known member
Like I said, 1A isn't much for 3.3v. The crashes under load are a tell tale symptom. I would be pretty surprised if a beefier regulator or different PSU didn't sort it.
 

Jaek_3

Well-known member
Like I said, 1A isn't much for 3.3v. The crashes under load are a tell tale symptom. I would be pretty surprised if a beefier regulator or different PSU didn't sort it.
In addition to the stock PSU my CC also has a Mean Well EPS-45-5 installed (40W, 5V, 8A). Is that not sufficient? I've noticed that when the logic board is fully populated with a G3 card, max RAM, an ethernet card and a GPU, the CRT seems to sort of struggle to turn on. It takes like 10-15 seconds for the CRT to finally light up and I can hear the high voltage engage one or two times before it finally succeeds. This doesn't happen with another, weaker logic board installed.

As for the 3.3v regulator, do they sell 10amp 3.3v regulators I can replace my current one with? Or would it be easier just to replace the Mean Well PSU altogether with something a little beefier?
 

Byrd

Well-known member
Hi Jaek_3,

Not withstanding possible PSU issues (and you should be OK with that additional MeanWell unit), the startup delay with "the works" installed could potentially be due to hardware initialisation or RAM check delay. Same goes with your choice of GPU - I never had success with an ATI Rage 128 in a TAM (and 5500), because of driver conflicts with the onboard ATI Rage IIc. In fact with these two cards installed I could get acceleration on one card with driver switches, but not both. I'm tempted to try a Voodoo 2 or 3 PCI card next to avoid the incompatibilities.

Going onto PSU issues though, I can confirm on a completely recapped CC with G3 (no additional power apart from 1A 3.3V regulator for PCI), it doesn't take much to tip it over in terms of power draw. I had to install a 2.5" IDE HD in mine to get it reliably booting with a USB 1.1 PCI card, anything more (PCI VGA, full size 3.5" HD), it wouldn't boot.

Lastly, point a desk fan at the internals with "the works" installed to rule out overheating, does your CC have an additional fan installed on the side of the case? A common mod was to cut away at some of the shielding and plastic internal skeleton to install a relatively high speed 80 or 90mm fan inside. With G3 + GPU it will overheat using the stock fan.

JB
 

Jaek_3

Well-known member
I'd like to verify the 3.3v situation; would it be possible to temporarily hook up a desktop ATX power supply to just the logic board, leaving only the CRT powered by the stock PSU? I'd turn the ATX power supply on, then the stock one inside the CC, and then pressing the power button on the keyboard should be all I need to do to turn the computer on, right?

Would any of this work?
 

Phipli

Well-known member
I'd like to verify the 3.3v situation; would it be possible to temporarily hook up a desktop ATX power supply to just the logic board, leaving only the CRT powered by the stock PSU? I'd turn the ATX power supply on, then the stock one inside the CC, and then pressing the power button on the keyboard should be all I need to do to turn the computer on, right?

Would any of this work?
You'd need to common the grounds between the two supplies, but otherwise you could power the computer lile that.

Do you know the ratings of the built in powersupply and your current auxiliary power supply? You have commoned the grounds between them haven't you?
 

Jaek_3

Well-known member
You'd need to common the grounds between the two supplies, but otherwise you could power the computer lile that.

Do you know the ratings of the built in powersupply and your current auxiliary power supply? You have commoned the grounds between them haven't you?
Yes, the new PSU is mounted directly to the metal shield of the old one via some metal stalks. I can common the grounds between an ATX PSU and this one just with an alligator clip, right? Is there an optimal place to source the ground on the ATX PSU or can I just get it from a ground pin?

As for the ratings, the auxiliary PSU is marked 40W, 5V, 8A. I really don't know about the stock one, though.
 
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Jaek_3

Well-known member
Lastly, point a desk fan at the internals with "the works" installed to rule out overheating, does your CC have an additional fan installed on the side of the case? A common mod was to cut away at some of the shielding and plastic internal skeleton to install a relatively high speed 80 or 90mm fan inside. With G3 + GPU it will overheat using the stock fan.

JB
Thank you for your response, Byrd. I do already point a desk fan at the internals of my CC, but that brings up another point: one of these days I'd like to install a fan of some kind inside my CC in addition to the PSU fan already present to help cool the fully decked logic board. Does anyone have any experience with this?
 

Jaek_3

Well-known member
Hello everyone, quick update:

I hooked up an external PSU to just the logic board on a bench completely disconnected from the stock analog board and PSU. The CPU fan and HDD started spinning, but no video from the ATI card and no chime (from external speakers). Nothing blew up. I've double checked my wiring and tested the voltages and they all seem fine, so I'm thinking I'm going to have to try this again with the analog board and CRT connected.

I'm thinking I'll plug the stock analog board and the external PSU into a single power strip, and then flick the switch. That way both receives power simultaneously.

Any comments or advice?
 

CircuitBored

Well-known member
Any comments or advice?

Do not power the machine up with the analog board disconnected from the PSU. They are dependent on one another. I have done this, do not do it.

I'm not sure if that was actually your plan but I wanted to put that out there just in case.
 
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Jaek_3

Well-known member
Do not power the machine up with the analog board disconnected from the PSU. They are dependent on one another. I have done this, do not do it.

I'm not sure if that was actually your plan but I wanted to put that out there just in case.
Unfortunately I've already tried it. It should still work though, right? I don't see how anything could have been damaged.
 

CircuitBored

Well-known member
Unfortunately I've already tried it. It should still work though, right? I don't see how anything could have been damaged.

The power drawn by the AB is required by the PSU for it to operate properly. AFAIK the "PSU" and "AB" are actually a weird co-dependent mix that is split across two boards.

On the PSU there is a large resistor with a very high value that will fail if you power up without the AB connected. This was my experience with a 5400, which I believe has the same LG-made PSU/AB.
 

Jaek_3

Well-known member
The PSU and the analog board are combined in the CC and neither of them was connected. I plugged power straight into the logic board.
 

Byrd

Well-known member
The 3.3V voltage issue on a Takky is only important to the Commslot and PCI slots, if you pull both cards see if you get more stability. Take it in steps over putting everything in and crossing your fingers, trying random PSUs. Do you have the original 5400/5500/6400/6500 units to also troubleshoot?

I'll post pics of mine soon, but I put in a 70mm slimline fan (I think) next to the RAM slot with parts of the plastic neatly removed to pull air from outside the case. This has proved adequate for cooling, prior to that it had a 60mm screamer in there (not my mod)
 

CircuitBored

Well-known member
The PSU and the analog board are combined in the CC and neither of them was connected. I plugged power straight into the logic board.

Ah, I was confused by the mention of a 5500 above and thought that was the system in question. My mistake, sorry!
 

Jaek_3

Well-known member
Hello everyone,



I had some time today to work on my Takky. I’ve fully reassembled it and everything’s working as it should.



The CC is totally stable until it’s placed under heavy load. Even with a PCI ATI card installed, I only get crashes trying to run complex 3D games.



Unfortunately I don’t have a 5500 on hand to troubleshoot with as I bought just the logic board from eBay. I’m thinking I’m going to replace the PSU I added to provide the logic board 5V with a beefier desktop ATX PSU I’m going to run outside the case temporarily, just to confirm whether or not the issue is power related.



I can say that without the 3.3v regulator installed, the machine crashes as soon as the Sonnet extension is initialized, which I think strongly suggests a problem with the 3.3v rail. Moreover, I’ve been able to confirm that the wiring I used to install my regulator is only actually capable of transmitting like 0.5amps, so all along the computer has been getting even less than the measly one amp the regulator is rated for!
 
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