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

[Toasty]

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

20v is quite an improvement.

Test the voltage across mains at standby with no load. Should be ~310v. Then, jumper the unit on and check again. Report.

Low output 3.3/5/12 when on and loaded is indicating PFC not "kicking" high enough. The small caps will affect that.

[gogo75]

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

And the results-nothing changed except 300V on main cap.

Main suply 220V,STW20NM50 are new,from same tube,every replacemant is exact value/may be crap caps,but same value/.
Any ideas ...???
I traced the KA3504-PGin and PGout not connected,+12V current sense too.

[Toasty]

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

280v is low. What is your mains voltage and why is it not filled in in your profile?

Take your mains voltage & multiply by 1.414. That gives you the standby voltage on the main cap. It will rise significantly to 350v or better when powered on, as the PFC comes online.

A weak mains cap is a possibility. Or the switchers were not replaced with the correct part or are not matched to originals.

[gogo75]

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

Thank You!
And what about Rubycon?I have one 470/400V(used) and I'll try it tomorow.Small caps no matter crap or not must work at least 48 hours.I'm gona replace only main,cose see R107-current sensor for PFC.
Bad main cap will draw more charge current,right?

And one more thing:
with those loads except 12V/not load on line 12V/, 5V become 3.8V and 3.3V become 2.98V

[Toasty]

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

Fujicon are crap.
Yageo are crap.

You have replaced crap with crap. No wonder it won't run properly.

[gogo75]

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

All small caps are Fujicon RK,main filter cap YAGEO LG.
PSU is open,on table.Test with resistors(resisitive wire) and with water rheostat.
Voltage acros main cap is 280v-no load,255-260v min. load.

Normal load-acording to label on PSU
3.3V-2.0 to 17A /in my case-2.3A
5V- 1.0 to 20A /in my case 1.3-1.4
12V-1. to 16A /in my case 1.4-1.5
-12V-0 to .4A / abbout 30mA
25Vsb-0 to 4.2A /bulb 24V/5W
5Vsb-0 to 1.5A /bulb 6V/3W

[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?

[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?

[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.

[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.

[uffda_oi]

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

!

[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

[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.

[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.

[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

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

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

Toast

Yeh, me too

Thanks for the feedback.

[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

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

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