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Quadra 950 PSU died... <cry>

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Hey gang,

 

I could cry like a baby... Restaurated my Q950, cleaned it, gave it a nice retrobright sunbath, tidied-up the A/UX installation and being annoyed by the loud fan, I went for the final step replacing it with something more silent and while at it, I gave the PSU a good blow of fresh air to undust it.

Power-on and..... bzzzzzzt, poof, holy smoke. The PSU went the way of the dodo :cry: (Nope, the polarity of the fan was correct) - Only god knows if it was the undusting or just about time to die...

So here's my request for help:

 

a) How do I get that damn PSU opened?! All screws removed and it's clear that there are 2 case parts sticked together but they don't move a bit :-/

From the outside I can see a bursted varistor near the back-end of the PSU. So that's where the smoke came from...

b) Does anybody know where to get a new Q9xx PSU preferably in Europe (given its weight)?

 

Thanks for helping & Cheers, 

Axel

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Plenty of space to throw a standard ATX PSU inside the shell of the original PSU together with the logic to get soft power to work.

That‘s my plan B in case the WGS95 PSU blows.

 

I had my unit open for de-dusting. You have to remove all screws and then slide the two pieces apart somehow which then will let you hinge them open. There are PCBs on two sides of the PSU and you won‘t be able to completely open it without removing wires connecting both halves.

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Thanks for helping everyone!

1 hour ago, Bolle said:

I had my unit open for de-dusting. You have to remove all screws and then slide the two pieces apart somehow which then will let you hinge them open. 

That somehow is what troubles me. I huffed and puffed and and... got a cut in my finger :-/

@Bolle: Is the logic for the soft-power (tickle) on a separate board? That would render the ATX PSU replacement into a real option.

 

So while @Unknown_K's hint "open it up and see" is a good one I'm still stuck at "open it up" - and I don't want to ruin the case (too) or get more cut fingers.

Is it possible that I have to somewhat pull out the wire harness going to the mainboard-connector?

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A long time ago I had a Q950 with a PS that went dead. So I looked around a long time and found a guy with a couple 950's he wanted gone an hour drive away. So I got the 950's for free and I removed the PS from the dirty one (other one was a new WGS95) and put it in the dead unit and it fire up. Just for fun I put the dead PS into the donor unit and it also fire up. Since they both worked (and still do) I never bothered to look into it further.

 

Old power supplies can act weird and some part smoking is not the end of the world. I did open up my supply to get to the fuse but that was a decade ago and I forget what was involved in opening it up.

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For such a massive overpowered, well ventilated PSU (akin to that in a server), the Q900/950 PSU seems to have some weaknesses.  Bolle's idea to shoehorn an ATX PSU in the case once it dies is excellent.

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On 7/9/2018 at 8:32 PM, Bolle said:

Plenty of space to throw a standard ATX PSU inside the shell of the original PSU together with the logic to get soft power to work.

That‘s my plan B in case the WGS95 PSU blows.

Because there was no alternative, that's the route I took... and hey, Lady Quadra is alive and kicking again! :wub:

For those who will ever be in the same situation, here's the how-to with pictures and stuff: Fixing the Quadra power-supply

(Ah, and the correct pinout of the power-plug - which is documented wrong elsewhere...)

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You could even cut out the part of the original PSU containing the drive connectors and wire that in.

Saves you from making a new PCB. Gotta keep things cheap once you started this way :evil:

 

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20 minutes ago, Bolle said:

You could even cut out the part of the original PSU containing the drive connectors and wire that in.

Saves you from making a new PCB. Gotta keep things cheap once you started this way :evil:

 

That was my initial thought... then feature-creep struck :wink: And who knows when I actually find the time to fully draw that PCB...

And we all know: Makeshift solutions last the longest.

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On 8/16/2018 at 11:57 AM, GeekDot said:

Because there was no alternative, that's the route I took... and hey, Lady Quadra is alive and kicking again! :wub:

For those who will ever be in the same situation, here's the how-to with pictures and stuff: Fixing the Quadra power-supply

(Ah, and the correct pinout of the power-plug - which is documented wrong elsewhere...)

 

Yeoman's work. I enjoyed reading your walkthrough and am assessing my ability to grab an ATX PSU and try it myself. When do you expect to be able to start whittling down your to-do list?

 

  • the PCB to continue using the (up to 4) 4-pin power connectors?
  • the soft-power circuit
  • a temperature fan speed controller
  • (optional) internal 5¼” power-connectors for solder-free connection to the external 4pin connectors.

And a pair of dumb questions:

 

1) is there a decrease in power consumption at the plug in moving to a more modern PSU? Therefore, wisdom in proactively rebuilding working units?

2) did you replace the fan while you had everything opened up and is there a noise difference?

 

Thanks!

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On 9/21/2018 at 6:32 PM, pb3623 said:

 

Yeoman's work. I enjoyed reading your walkthrough and am assessing my ability to grab an ATX PSU and try it myself. When do you expect to be able to start whittling down your to-do list?

[...]

And a pair of dumb questions:

 

1) is there a decrease in power consumption at the plug in moving to a more modern PSU? Therefore, wisdom in proactively rebuilding working units?

2) did you replace the fan while you had everything opened up and is there a noise difference?

 

 

Thanks, glad if this is useful for somebody else! 

 

As for the todo-list:
I need to "clean" the remainders first as I promised the parts to someone else who is on the mission to repair an old PS "the correct way" as @techknight would probably say ;-)
Hopefully this is been done this week - suffering severe vintage-project-ADHD I got dragged into other realms of resurrection (http://www.geekdot.com/the-mips-rs2030/) and need to force myself to return to the good ol' Macs (not to mention the SE/30 vs. Carrera040 riddle still waiting to be solved)..

 

1) Well, there's certainly a higher efficiency with good, modern power supplies.  This means it will waste less watts coming "from the wall" to feed you Quadra, i.e. saving $$$

That said, mine is a crappy, cheapo and example of bad engineering, so I doubt it's that much of a saver. OTOH lady Quadra is not running 24/7 so the impact is negligible.

2) Yes, you have to have the case open no matter if you're planning to replace the fan or keep the original one. This is because you have to somehow adapt & connect the new or old fan to the replacement PS.

The noise level is of course related to the fan quality you choose. I picked an average one (~10€) which is much more silent than the original one. You can probably go some db lower by spending the double amount.

 

Again, there's a nota-bene: The PSU fan ist the only fan for the whole system - a principle many vintage machines followed (read SUN/SGI and the like). Thus the fan had to pull the heat through the PSU while having enough juice to cool the PSU, too.

So todays measure of "CFM" ( cubic feet per minute) isn't sufficient to choose the right fan for an original PSU: You have to make sure the static pressure (which tells us how good the fan is at sucking air over various objects at its intake) is within the specs of the computer manufacturer.

Here's an example from the SGI-World: The EBM Papst 8412N running at 3100rpm has a CFM of ~40 and a static pressure of 4 while the often used & modern Arctic F8, delivering a nice CFM of 30 @ silent 2000rpm, has a static pressure of just 1.  Not enough to cool the computer itself. It'll cook itself to death sooner or later. It's a bit like horsepower vs. torque with cars.

Figureing out all these specs is quite hard today.

 

Again, because you bravely swapped your Quadras PSU to a newer, modern one you don't have to care about this as these PSUs aren't getting that hot and an average PC fan is just fine - not sure how much this is true for a fully loaded Q950 with PPC accelerator and 4 hard-drives, though.

 

P.S: A nice side-effect: My Q950 is much lighter now! You can really feel the difference when hauling the beast around...

Edited by GeekDot

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