PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

[ran]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

so, how did your recapping go? I'm still awaiting info on what to do with mine...though the thing has depreciated so much.. just..sitting there...... *sigh*

I'd like to get the PS fixed...but I really am just not sure what I need to get......

[Toasty]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

Recap was fine. Basically an all "vent" caps, recap. Found some small bad ones next to the PFC board too. You have to pull the larger heatsink, as I said before, to get to those caps and to get the switchers done.

Mains cap, fuse, both switchers (Q1,2).

Toast

[bambinos]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

Hi All.
I'm trying to repair the same PSU with the same problem - "Mains cap, fuse, both switchers (Q1,2)" Can I replace swithers with W20NM60FD? I've read datasheets on both W20NM50 and W20NM60FD, it looks possible except R(ds) - 0.25 and 0.29 respectively? Or is it not so important?

[billabongo]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

@ Toasty

Sorry to dredge up an older thread. But just had a quick question

I have 2 of the samsung power supplies identified here. I have also identified all the failed components through bench disassemble, however...

The Thermistor on both my units had failed and the part # is not legible for the original and obviously were not testable for resistance etc.

You had identified a replacement below

http://search.digikey.com/scripts/D...ame=570-1046-ND as a 10amp with
R @ 25c = 2.5 Ohm
R @ Current = 0.04 Ohm

I have had an order all the parts through Digikey for awhile now, but the part is still on back order and looks to never come in at this rate.

I am looking to find a alternate and have found another unit of the same brand but with different resistance

The other unit is

http://search.digikey.com/scripts/Dk...me=570-1055-ND

R @ 25°C 7.0 Ohm
R @ Current 0.08 Ohm

I am thinking that the resistance is way to high, but since I don't have a reference unit to get original readings from, I wanted to see what you think of the part.

Thanks

[Toasty]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

@ bambinos - Should be fine. Higher voltage and current rating. Make sure it's the TO-247 package you're comparing on the 20NM60. Both at DigiKey at this time.

@ billabongo - Go to DigiKey search.
Enter: Inrush Current Limiter in the block. Click GO button.

Scroll down until the selection blocks are visible.

- Check the In Stock box
- In the R @ 25°C column, select 2.2 thru 3.0 ohm
(Press Ctrl and click each value -or- press Shift and click the first and last values)
- In the Current - Steady State Max column, select 10A thru 15A
- Click the Apply Filters button

You should have 4 choices in the filtered table. I'd go with the Ametherm one, which is the same brand as the one they're out of. Should work just fine.

Toast

[billabongo]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

@ Toasty,

Thanks for the tip... I did not think to go above 10A ratings in my search, but it worked like a champ!

I got the parts in and have repaired one unit and its now happly powering a MDD Dual 1.42 system.

The parts replaced:

Mains Cap
Most of the vent caps
both switchers (Q1,Q2).
Thermistor (TH2)

Both units had the same failed components, so it would appear to be common on the samsung units.

Now for a kicker, While removing the heatsink to replace the switchers on unit #2 I forgot to unsolder the leads to TH3 and severed them

Since the other unit is back in service and operational, I again don't have a reference for part #.. I did while the other unit was repaired managed to get 86.4 Ohm reading from the other unit (at room temp 75f).

TH3 is tiny and bolts to the heatsink via a small metal bracket.

I was wondering if you had during your tear down and testing/repair happened to get a part # for TH3.

[Toasty]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

"I was wondering if you had during your tear down and testing/repair happened to get a part # for TH3."

No. Sorry.

[billabongo]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

@ Toasty,

Thanks anyways.

So I took the part of the heat-sink and there is no markings or part # on the bracket or Thermistor.

Taking closer inspection, it appears that the Thermistor was glued into the metal arm for bolting to the heat sink due to very limited air flow or to prevent damage or short against the heat-sink upon installation.

I have been able to determine that the Thermistor is aprox 3mm and lead spacing of approx 2.50mm - 3mm

Plugging in the dimensions there is really only 2 units to choose from

http://search.digikey.com/scripts/Dk...me=570-1088-ND

and

http://search.digikey.com/scripts/Dk...me=570-1087-ND

The Ohms rating varies greatly between the two.. my measurements were 86.4 Ohms with the meter on auto.

[Toasty]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

Marking on ring tab: 10850

Measures ~85Ω @ room temp

When heated, it seems to "trip" to a high resistance of over 200Ω. It is not linear in it's resistance compared to temperature and seems to be more of a switch than thermistor. It is connected to the PWM board nearby and is most likely for thermal overload protection.

Might try some old PSU's for a similar type device.

Toast

[billabongo]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

@ Toasty,

Thanks for the info. This is pointing me towards what I "think" is needed.
I really appreciate the help.

So going off what you have discovered and that the values increase based on temperature, I searched high and low for a thermal switch

Below is my results and looks to be the closest match I could find.

There are 4 available temp cutoff points, according to the Data-sheet.

Here is a pdf link for the product, under TS3 Series Moxie (figure 3 style):
http://onlinecatalog.digikey.com/Web...ageLabel=2141#

Switching temps are 57, 65, 75, and 85c

Now I would probably go with the 85c as the board components get pretty hot lol.. So I just need to guess on a median temp cutoff point.

[Toasty]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

The Moxie are NTC (like TH2). You need PTC. Resistance increases with temp.

[Kansas Sparks]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

AND NOW… 7 years after the last post on this thread, I'm on here asking if there's anything new in this process (as in: a *simple* PSU “remove old and replace with new” replacement for these old PSU's), or am I destined to begin the recapping and test procedures noted herein? I've two of these (still), working G4 MDD's that now… just after turning 14 years old, might indeed be waay past due for some “brain salad power-supply surgery”. Like to see ‘em both go another 14 years.

*as if “simple” is possible.

And maybe this is covered here, elsewhere (under Dual 1.25 and/or Dual 1.42), perhaps?

Okay, I'm very new here, start throwing things. Forgive me.

[Viking_2018]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

Hello Folks!

Old Thread, but some idiots (that'll be me), are still using Mac G4 MDD machines.

Two, in fact!

Both G4 MDD Single 1.25 GHz, both from 2003, both bought new in around 2003/2004, but one has failed, and the other is looking suspect.

So, one is still working, but its main Fan breathes up and down like an old man on his last legs, so needs a good check over. I am not willing to take that one down, whilst it still works, until I have the other one back up and fully operational again. Then I will rebuild the main one, using the lessons learnt fixing the non-operational one.

The second (non-operational) G4 MDD became problematic several years ago, with random shut downs and then a very random reluctance to re-Boot, so that one got pulled to storage and was then forgotten about.

I retrieved the latter from storage about a week or so ago and found that it Booted!

Well, sort of.

It Booted to Mac OS 9.2.2 but hung just before the Desk Top fully came up.

I found that it must be a bad Extension, because I was able to Boot that one if I turned off Extensions.

So, I gave it a good clean, changed the 3.6V PRAM Battery, removed Heat Sink and cleaned both it, and the CPU, then re-Seated the Heat Sink with Arctic Silver 5 Thermal Paste. Re-Seated AGP GPU and RAM. Then re-configured this G4 MDD with a new 120GB SSD (via a small StarTech IDE to SATA Conversion Board, acquired via Amazon), electing to take this new Configuration up to Mac OS 10.4 (fully patched), and Adobe CS2.

All was going well, when this rejuvenated G4 MDD suddenly shut down, and then was reluctant to Boot thereafter. It was about then that I remembered just why we had pulled that machine (random Shut Downs).

OK, looks like it must be the PSU.

This one is a UK Machine, so has a 240V PSU, namely a AcBel 360W. The PSU's Main Specifications seem to be:

AcBel API1PC36 REV: B 360W

+5.0V - 20.0A
+12.0V - 17.0A
-12.0V - 0.4A
+5.0V - 1.5A
+25.0V - 4.2A

I am a complete novice when it comes to replacement of electrical components but, am keen to learn, and am not about to do anything daft.

So far, I have disassembled the above G4 MDD, and have the AcBel PSU out.

The Links below are to Amazon or eBay, so that others can find these items, if interested.

I may wimp out and just fit a PC Corsair ATX VS 550W PSU, already acquired, including an ATX Break Out Board, plus an ATX 8 inch Extension Cable so that I can hack that around to re-jig the ATX PSU's pin-out to match the Mac G4 MDD pin out (without compromising the ATX PSU's own cabling).

I am aware of the missing 25.0V feed, so have ordered a Ramp Up Transformer (12V to 24V 3.0A), so may fit that to provide the 24.0V needed to retain Mac ADC Display Functionality.

I am at the stage of working out how best to cram the box brick of a PC ATX PSU into the G4 MDD Case. There is room, so it's just a case of making a tidy job and keeping it clear of PCI/AGP Cards as the Side Door closes, and making sure the Main Fan's air flow is not compromised.

However, as I have a second G4 MDD that will also, in all likelihood, also need the PSU sorting, I may take the AcBel apart, and see what I can see. Alternatively, I may also just go for an ATX PSU, and mirror the set-up I am embarking upon to the (currently), failed G4 MDD.

If I find out anything interesting, such as a list of UK based components that can be obtained to fix a poorly UK 240V AcBel 360W PSU, I will update.

Likewise, if anyone else in the UK has already fixed a poorly AcBel 240V 360W PSU, and has a list of components and suppliers, please do let me know, if possible.

Viking2018

[Viking_2018]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

Hello Folks!

Brief update, sadly, if that's the best way to put it, I cannot see anything visually wrong with the Mac G4 MDD's PSU.

No burn marks, all Capacitors look fine, none are swollen, and there's no obvious sign of any issues anywhere else.

I'm pressing ahead with Plan B, the fitting of a PC ATX PSU, but may come back to the Mac's original PSU. Obviously, I need to start doing some testing, but it is an old 2003 PSU, so I could be wasting my time if the brand new Corsair PC ATX PSU upgrade solves all issues.

The PC ATX PSU is a sod of an awkward shape to fit, because the main Fan, Cables and AC Input and Mains Switch are all on the most awkward faces of the cube to fit it straight in. I think I may have found a couple of alternative locations:

(A) Cut down the Optical Drive Cage, fit the DVD in the lower of the two slots, and mount the ATX PSU above that, and within the modified Optical Drive Cage (albeit sticking out of the top). The advantage there is I can retain the DVD Drive, and this will vent the main PSU fan upwards, and away from the CPU Cooling. I will cut down the old PSU's metal case, and will modify a Kettle Lead and solder one end of that to the original Mains Input, so that it can still be used from the rear. The other end will then plug into the PC ATX PSU.

(B) Cut a hole in the roof of the G4 MDD Case, and fit the PC ATX PSU up high and to towards the front, so that the main PSU Fan vents upwards and straight out of the Mac's Case. This gets it up high and out of the way, but will interfere with the securing screw for what is left of the old Mac PSU's Case (that I will cut down as above).

Either way, I was thinking of using the rear back plate of the old Mac PSU, as a Mounting Plate for SSD Drives, and also possibly a location for the ATX Break Out Board that I may use when wiring the ATX PSU's main Cable to the Mac's 24 Pin (via an 8 inch ATX Extension Cable so I do not need to cut the ATX PSU's Cables).

Of the two, fitting the ATX PSU into the Optical Drive Cage has the advantage that the Optical Drive and PSU can be removed as a complete unit, just by undoing two Screws, plus pulling out the internal Kettle Lead, and the MOLEX Power and IDE Ribbon from the Optical Drive.

As I still have a working Mac G4 MDD, I remain interested in looking at the original Mac G4 PSU, to see what is actually wrong with it. The other Mac may well need a similar solution, depending on how well the above PC ATX PSU fitting goes.

One day, we will have moved all Design work away from Mac OS9 and older Adobe Software, when the two Mac G4 MDDs will be surplus, so I may then contemplate stripping them right out internally, and going for a Hackintosh conversion. Plenty of workable options there, water cooled CPU seems to fit very well into the Mac G4 MDD Case, but the main target is reliability.

A machine that shuts down at random, is no use to man nor beast.

OK, I will press on with the PC ATX PSU Plan B task, and will update. Then I will see what I can find wrong with the Mac's original PSU.

It's also possible that the shutting down issues were not PSU but, say, some issue with the MotherBoard or CPU. Fastest way to tell that is to get what should be a new PSU fitted, and see if the Mac comes back to life, or if it has non-PSU issues.

Viking 2018

[bzyzny]

Re: PowerMac Dual 1Ghz Mirror Drive Pop&Burn Power Supply

Just wanted to say thanks to everyone in this thread, and the other related threads on here. Recently I repaired one of these power supplies thanks to the info on here and the capacitor list found on thehouseofmoth dot com. I had to do some digging to find suitable replacements for some of the parts, since I couldn't find them in stock from a reputable source. Here's a list to hopefully help the next person. The bridge rectifier and mosfets have slightly different specifications but they worked for me. Please verify for yourself that they are correct replacement parts for your PSU.

Digikey part numbers
Fuse: 486-1767-ND
Bridge Rectifier: GBU8JFS-ND
Mosfets: 497-3263-5-ND
Main cap (390uF 450V): 493-3238-ND