Power Mac G4 MDD "Mirror-Door" won't power up

[Mh4mac]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

I chipped it while removing the toms of white silicone the put all over the board. THANK YOU! This is the last Samsung I have and didn't have another to match with. Thanks a bunch Toasty ;-)

[uffda_oi]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Success!

Problem: the main cap failed open and ultimately shorted out one of the MOSFETS and then fried a thermistor managing surge coming in on startup. I followed the steps in the other forum post and presto!

Some pics and comments on the process:

Scorching evident on the yellow coated heat shield from the fried thermistor:

A belated "thank you" for this well-illustrated repair log.

I just finished "repairs" on two Samsung PSUs and broke the wires on the 4th component from the left in the first IMG (the blue disc in shrink-wrap).
I think, with the help of "wiki," it is a MOV (in LF2, next to and at 90º to TH2). The lettering says:

JEC
JD47 2M V1

250V 400V X1
400V Y1

The shrink-wrap in Keith's picture says 125º

I can't find a replacement for it at Digikey, et al, and would appreciate help with the ID of this component.

The PSU with the broken LF2 does not light the test lamp. The other PSU lights the test lamp in the following pattern:

Bright--> dim--> several bright blinks--> off

My test lamp was derived from Toasty's circuit. It uses a scrap of lamp cord. One line (red clip) goes through the bulb, the other (black clip) goes directly to the PSU.

It is my one success so far.

[Toasty]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

It's an X or Y cap, depending on how it's wired.

Mains to ground - Y
Across mains - X

472M = 4700pF - 20% tolerance

250-400v as an X
400v as a Y

Toast

Furthermore:
Y1 is double insulated and insulation pulse tested to 8kV DC.
X1 is insulation pulse tested to 4kV DC.

Do some Googling. You could spend hours...
.

[uffda_oi]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Thanks for the tip, Toasty. This hint should get me closer to lighting up my PSU (in a good sense, that is).

[Toasty]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

See:

http://search.digikey.com/us/en/prod...2414-ND/790170

DigiKey #: 445-2414-ND

[uffda_oi]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Toasty (and others)

Thanks for the help. I LIKE this forum!!

I've been hanging out here wondering if I could actually fix my power supplies. The helpful and well illustrated accounts of repairs got my courage up.

Yesterday I thought I had done in two Samsung PSUs. My wiseguy test lamp did a cute light routine (bright --> dim --> a few bright blinks --> off).

It did not light at all with the other Samsung I had worked on. So, given my winning streak, I switched out the big cap on my only working PSU (a third Samsung) and, lo, my wiseguy test lamp did the same cute routine. I figured I was cursed but put it back in the G4 1.25 Mhz MDD anyway. It fired right up. Success!

So I switched out the ailing AcBel PSU in my G4 1.25 Mhz dual MDD and the third Samsung also fired right up. This is the power supply with the broken x/y cap. I did a hack mend job on it yesterday but assumed that it had failed the light bulb test.

Now my G4 dual is very fast! The power light stays on and the computer doesn't have to be unplugged before each start. I still have plenty to do and feel very fortunate that there are experts here that take the time to help the less gifted.

I'll buy a few x/y caps in a larger future order. There is something about a $.50 order...

I LIKE this forum!!

[Toasty]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

The mains cap -must- be -replaced- if it is the CapXon HP series. (390uF/420v)

There is a manufacturing error/failure within this series of cap. If it goes open, you'll be back in there pulling it out, the 2 mains switcher MOSFETs, plus the fuse, and possibly the ICL thermistor.

At $6.18 each for the MOSFETs plus the cap at $5.23, you're better off replacing the cap now. Add that to the fact that you must remove the heatsink assembly (with 5 additional components attached) that the switchers are mounted to, in order to change them.

Toast

[uffda_oi]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Sage advice from Toasty as usual.

This post is to avoid a penalty for unnecessary celebration in my previous post.

My project includes

3 - Apple p/n 614-0224 Samsung power supplies

1 - AcBel (see pic of label)

These units are in Apple Powermac G4 MDD machines

Work completed:

R&R components using UCC caps in two Samsung units as per suggestions by badcap veterans.
Both the 390uF@450v tested zero so removal of the big heat sink was indicated. So was the "while in here might as well replace the usual suspects" principle.

1 - 390uF@450v
2 - 56uF@250v (C135 and C137)
1 - 47uF@25v (C141)
1 - 22uF@50v (C129)
1 - 10uF@50v(C130)
1 - 5x20mm 8A@250v ceramic fuses
2 - N-CH 500v 20A to-247 MOSFETS (for Q1 and Q2)
1 - inrush limiter, 4 ohm 9.5a (TH2)

One Samsung works (with a damaged x/y cap (LF2), to be replaced) and the other does not. I suspect first effort wear and tear to the circuit itself.

Samsung #3 had blown a fuse and was suspect. I replaced the fuse and put it back in service. Later, I replaced the 390uF@450v cap as insurance. I have enough parts to complete the whole job.

The Acbel was taken out of service because it made the computer goofy (had to be disconnected before each restart, lost PRAM, frequent freezes; false clues about the PMU and NVRAM, CPU, and logic board). The Acbel is a future job (after solder iron burns heal up).


Digikey had everything.

[Toasty]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

An X/Y cap won't keep a supply from running, unless it is shorted.

The blink routine for the test lamp is normal. It's the caps and circuits charging up that makes it blink. When it comes on and stays on with no load, that's when there are problems.

Sorry. I thought you had swapped a main cap from a bad unit. Got very lost dealing trying to sort out 3 supplies in one post.

Toast

[uffda_oi]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Got very lost dealing trying to sort out 3 supplies in one post.

Toast

Yeh, me too

Thanks for the feedback.

[uffda_oi]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

p.s. If you saw my mend job, you would propose I switch out the bad x/y cap -now-.

The sick Samsung showed a little life after solder was applied to the two power input pins (but still in IC).

[uffda_oi]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

The attachment shows my first attempt at repairing anything electronic. It shows the "job" I did on the circuit. This is the mistake I am learning by.
I may have damaged a trace or let solder flow where it shouldn't, especially top center in the area of the single post of the heat sink and the pair of Mosfets. The board has a hacked at look, huh. I plan to pull another Samsung PSU as a guide to de-blobbing. Comments would be greatly appreciated.

[uffda_oi]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Lesson in humility for the day: a 30 watt famous brand iron is not hot enough for solder wick. Lesson learned. My hacked Samsung board may clean up with -proper- solder wicking.

[Agent24]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Solder wick is usually very good when it works, but if you don't have enough heat or a good thermal "bridge" then it just does nothing.

I see the areas you were trying to solder look connected to rather large fills, so probably you were sucking up too much heat there. Solder wick can also suck up some heat so your iron might be able to heat one or the other but not both at the same time.

Try a short piece of solder wick if you were holding the whole reel, to keep less mass and suck up less heat into it.

Also try adding fresh solder to the joint before desoldering and possibly add your own flux to the desolder wick. Some wick comes with flux in it, but some doesn't. Even if your does, if it's old, the flux may no longer work very well.

If you have a solder sucker, try that, since you only need to heat the board and not wick as well.

[Toasty]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

A 45w-60w typically needed here, with a substantial tip (larger mass). Or, a station capable of up to 800°F (425°C). I use a 100w gun type when working on the heat sink attachment points.

I find it surprising that you are working on the MOSFETs here without removing the heat sink assembly as a whole. Very difficult, no maneuverability, and near zero clearance. Coupled with the fact that 4 caps need to be replaced between the heatsink and the small upright board adjacent to it.

If you decide to remove it, be sure to be -VERY- careful with the temp thermistor. By your picture, it's located on the left side of the heat sink, the 2 vertical connections to the left of the marking r122a. Make sure the wires are straightened, the holes clear of solder, and the wires loose before trying to remove the heatsink.

Toast

[uffda_oi]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

!

[uffda_oi]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

agent24 and toasty

I assume you responded to message #73, my sly request for soldering tips. Your replies are most helpful and I learned more about equipment and temperatures. Actually, the job in #73 is after I reinstalled the heat sink. I started at the heat sink single post and my soldering got better as I went. This was done with my 30 watt famous brand iron. It takes awhile to heat up.

Some of the hacking came from the earlier desoldering, done mostly with the famous brand iron with the red bulb. It also takes awhile to heat up, enough to go have a snack while waiting. I now have a hotter iron and the solder wick works. Thanks for the advice. Every little bit helps.

[liko99]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Hello. I have the same problems. My Mac die last week I and wanna fix it. I search here for the supply but nothing. Only I found in ebay for 70 euro.
I cant read anything here because more of the information i don`t understand it.
Thanks
Regards.

[gogo75]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Hello from Bulgaria!
I had to repair one Samsung PSCF401601B(C).Started with "text book"-TH2,Q1,Q2,C122,D101,D102,C129,C130,C135,C137 & CC141.At that point all OK-I got the +5v sb & +25v sb and +3.3v,+5v,+12v,-12v with no load.
With load less than a minimum labeled on the cover no problems,but with normal load it shuts down.
Where I must look?SUB1 with PCF or SUB2 with KA3504?
Some measurement points?

[Toasty]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

What brand and series caps did you use? Numbers don't mean anything without correct replacements.

Is this failing when mounted in the machine, or on the bench testing?

>>but with normal load it shuts down<<
What do you mean by "normal" load?