iMac G5 17' ALS Aus psu

[ubermoo]

Hi all,

i need some help with diagnosing an australian "DD" imac power supply (Part number to follow when i find it's case)

Pic

I have replaced all the caps indicated, all of them had visibly failed, but the iMac still has the same problem it started with-
When plugged in to the midplane, the 5VSB is fine, but the 2nd led flickers and goes out when power button is pushed. (Single flash ~50msec duration) This is accompanied by a small high frequency squeak from the PSU.

I bench tested the PSU, i get +5VSB and +23V, but the power supply keeps turning on and off every second or so, giving a single squeak each time.

The rails all get power, the multimeter reading indicates that there is voltage on 3.3, 5 and 12 but due to the PSU turning off so quickly the readings never stabilise on the meter.

Is there a protection circuit that is kicking in? a bad diode to check? i would really appreciate a hand with this one.
i had a look at other threads but the only thing that is mentioned is ZD4, mine is fine.

thanks guys.
Matt

[PCBONEZ]

Re: iMac G5 17' ALS Aus psu

Here Toasty!
Here Toasty!
Splssssssplt
- I never could whistle.

Welcome to the forum.

Toasty knows the inside of MAC PSU's pretty well.
He should trip through shortly.
.

[ubermoo]

Re: iMac G5 17' ALS Aus psu

hey thanks pcbonez

i've made some pictures of the powersupply, since there doesnt seem to be that many photos of this variety of the PSU on the internet machine. i've attached them, i hope they display

it's an AC BEL 614-0325.

i've included a couple of closeups of the diodes around the join between the primary and secondary side.

the coils don't look damaged and have very marginal resistance between the windings but infinate across and to the chassis, i think i can rule them out.
none of the toroids are heat damaged.

would it be a fair guess that replacing the voltage regulators on the heat sink is a prudent idea?

[PCBONEZ]

Re: iMac G5 17' ALS Aus psu

> replacing the voltage regulators on the heat sink <
Should at least check them.

Those two caps with the 'barbed wire twist' vent stamp in the top are probably either craps or counterfeits.
No respectable brand I know of has ever used that pattern.
.

[kc8adu]

Re: iMac G5 17' ALS Aus psu

samwha?
i have seen a few sanyo with that vent too.

[PCBONEZ]

Re: iMac G5 17' ALS Aus psu

According to the Sanyo Rep I sent some counterfeits to for validation any Lytic marked Sanyo that doesn't have a K vent is a fake.

[Toasty]

Re: iMac G5 17' ALS Aus psu

*Pavlovian response*

Whistling typically begets a New York salute from me. With that attempt, a poncho was required. Is it raining??

Coffee works much better. Now where the hell did I put mine...?

Greetings ubermoo!

The tick-squeal of death syndrome, eh? Problem occurred due to bad original caps, but remains after recap which indicates it took out a component *somewhere*. It has been tough to narrow down. Plus, yours presents yet another variation to the circuit layout. Oh Joy!

The 14 pin chip on the back is a WT7515 pin out variation type 141WT. It is a 3.3/5/12v over & under voltage and over current monitor. Pin 3 is its output. If anything goes out of range, it shuts down the 3845B PWM(s) back under the bigger transformers. The 3845Bs run the (4) 11N60C3 MOS transistors on the 2 heat sinks between the transformers. A power cycle is usually necessary to reset at that point.

The voltage regulators are most likely fine. I'm thinking one or both of the 3845B PWM's is/are bad or the WT7515. If it's the WT7515, they are not available. If the output on pin 3 is constant high, it's a likely culprit. All the other chips are available.

Also, check the transistors in the PWM circuits (solder side). Usually marked 1P and 2F. Jeweler's loupe or electron scanning microscope necessary to read numbers... Going left to right with single lead on top - Base - Emitter on bottom, Collector on top. 1P is NPN, 2F is PNP. Should be 4 around each 3845B and 2 near each set of 11N60C3's.

I'll try and do some digging on the next model up ALS unit I have (614-0326) and see if I can find more info.

Toast

[techcaps45]

Re: iMac G5 17' ALS Aus psu

Are Rubycon PX series ok to use in the apple power supplies? The RX30 are too wide and MCZ/MBZ do not come in 10v or 16v 3300uF.

[relkin67]

Re: iMac G5 17' ALS Aus psu

Are Rubycon PX series ok to use in the apple power supplies? The RX30 are too wide and MCZ/MBZ do not come in 10v or 16v 3300uF.

I have a 4700uF/10V Ruby PX in the PS of my repaired iMac G5 17" rev A. Been there for months with no problem.

[Toasty]

Re: iMac G5 17' ALS Aus psu

>>Are Rubycon PX series ok to use in the apple power supplies?<<

Imac G5 supplies? Or another type? If Imac, what's the PSU's Apple part number? i.e.- 614-????

What was brand/series of the original cap you're replacing?

One type that was used there is(was) the Ltec LXY series. If that's the same cap, then PX is not good enough.

LXY - 3300/10 @ 12.5x25 = 2780mA / 17mOhms
Taking the more likely size of 10mm, the next closest in size down in LXY 10v is 10x23. Based on can size from that info, the cap is still 2170mA / 22mOhms. A PX in 10x20 is only 1100mA and there is no listing for the ESR.

Toast

[PCBONEZ]

Re: iMac G5 17' ALS Aus psu

Agree. - PX is a GP cap. - Not a good idea.

Rubycon ZL - 3300/10 @ 12.5x25 = 2770mA / 19mOhms
Chemicon KZE - 3300/10 @ 12.5x25 = 2770mA / 19mOhms
And better
Panasonic FM - 3300/10 @ 12.5x25 = 3190mA / 15mOhms

[Player2]

Re: iMac G5 17' ALS Aus psu

ubermoo- I just got done messing with a G5 that had the exact symptoms you were having. Did you remove the logic board to recap it? If so, make sure it is not shorting on anything. Loosen up the screws, reset the SMU, and try again.

It's kind of a longshot, but it's something quick, easy, and free that you could try.

[Sustain26]

Re: iMac G5 17' ALS Aus psu

Hi,
Newbie here; my ps from a G5 ALS 17" iMac died. I followed Apple's help file. The p/n is 614-0325, rev. A. Is anyone selling a replacement, or can repair mine (closest to Montreal, Canada or Vermont)? I can post pictures, just tell me what components to take a picture of.
Much obliged!

[Quasar]

Re: iMac G5 17' ALS Aus psu

Ebay has many. Most all of the iMac G5 PSU's are interchangeable, depending on the voltage you get from the outlet. If you're 115v, then any will work. If 220v, then ask what the unit is rated for on the label before you buy. Some are only good up to 125v.

Keep the ALS from yours (it just snaps on or off the PSU case) and get any other. It is not connected to the PSU in any way. I understand that you should stay clear of ones made by Celetronics. It's in a thread here on the forums somewhere.

Search the forums for imac G5 power supply and you'll have a lot of reading to do. Some of them are quite lengthy.

If you're considering fixing this yourself, you might want to begin a new thread.

Q

[timBe]

Re: iMac G5 17' ALS Aus psu

hello everyone,

ubermoo, did you finally fixed your PSU?

I started to fix an ACBEL 20" PSU PN 614-0326. Firstly recaped (secondary side), I had a bumped 2200uF bad cap (on 3.3V circuit), I measured 650uF only. All other caps where replaced but measured values were OK:
3200uF - 3140uF
1200uF - 1245uF
1000uF - 945uF
1000uF - 990uF
1000uF - 950uF
1000uF - 930uF
1000uF - 920uF
330uF - 355uF
120uF - 127uF
However, I also found Q1 slightly burnt, so I replaced all marked 1p transistors (2N222A CMS) around 3845B PWM driver. No other visible failed component on the board so I plugged the PSU: 5.1Vsb is 5.173V, and 24V is 20,528V. Good start.

Grouding the ON/OFF pin 15 to start up the PSU, it would go into protection after 1 sec because of votlages higher than required on 5V, 12V and 24V outputs. 3.3V is 3.31V, 5V is 5.86V, 12V is 13.4V and 24V is 26V.

Then I found I could get the PSU working with a small load of 100 ohms on 5V output (50mA load). I then replaced R95 (62 ohms) 5V output load by 33 ohms in order to have permanent internal load (150mA) to make the PSU working with no external load.

The problem is that my PSU is currently very limited. VoltageS are not well regulated. Loaded separatly, I have :
-> 3.3V output 3.26V@0.25A and 2.53V@0.54A
-> 5V output 5.08V@0.1A and 4.5V@2A
-> 12V output 11.76V@0.5A and 10.98V@3A
I have attached the full UI characteristics below.

Loading 12V output at 3A, I am able to sink 1.5A on 5V output (voltage is then of 5.061V), and I can sink 2.24A on 3.3V output (votlage is then of 3.2V). Hence I would say my PSU is limited to 41W output and voltage rails regulation are not independant at all.

Could someone tell me if it might be a bad current or voltage feedback? or a bad transformer?
Does anyone knows what are the approximate nominal loads of an imac G5 ?

[Toasty]

Re: iMac G5 17' ALS Aus psu

Unnecessary to replace all those 1P's. Only 1 fails.

Supply must be cross loaded. Not intended for 1 rail operation.

Please supply API number from board (not from casing). API #PC##
That identifies the board. Many were factory or aftermarket repaired, so cases and boards have been swapped along with 17" & 20". All the same.

Toast

[timBe]

Re: iMac G5 17' ALS Aus psu

Thank you Toasty for your fast reply. PCB is API4PC46-290 03L66-000
Do you need a picture of it?
Do you know what a typical cross load is for a 20" imac g5 ?
Anyway I will plug it back to the iMac tomorrow and see what happen !
I think I won't dammage the mother board electronics with under voltages.

Tim

[timBe]

Re: iMac G5 17' ALS Aus psu

PSU repaired ! imac is working fine now. Toasty was right to say it must be cross loaded. I still don't know what are the classic loads but I can tell you the following to summarise my findings:
- PSU was repaired by replacing 2200uF and Q1 (1P)
- full secondary side recap was done to avoid later capacitors issue
- my PSU (PI4PC46-290) is not working with no load (overvoltage protection), minimal load is 100 ohms on 5V output (50mA load).
- I replaced R95 (62 ohms) 5V output load by 33 ohms in order to have permanent internal load (150mA) to make the PSU working with no external load. However this was probably not essential. It is just more convenient for test purpose.

Thank you for everyone contribution here on badcaps.net, and thank you Toasty for your time and feedbacks.
See you

Tim,
a french guy that does not want to waste electronic products as recycling is an issue for today and tomorrow.