Apple MDD G4 PSU (AcBel API1PC36) - Recap question

[jantoman]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

Not sure that you do have the same symptoms as me... for me the fans did not twitch, they all started, and went top speed while the machine had no video output, and no start-up chime

Same symptoms here. The funny thing is that I replaced the original PSU with a brand new one... Apple had a "quiet fans" program for the MMD and his owner bought the whole set (PSU + fans) sometime ago "just in case". Last week his G4 stopped booting; we replaced the PSU with the new one, but the computer refuses to boot almost always. Maybe a cap was DOA.

I checked the original PSU but I didn't notice any bulged cap: I'll give it a closer look with the help of your pictures.

[Agent24]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

Not all failed capacitors bulge. Only way to know for sure is to test with an ESR meter.

It's possible the capacitors in the 'new' PSU went bad just sitting there unused. Doesn't happen always but it can if they are bad quality enough.

[Didius]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

Apologies for bringing the thread back to life.

I've recapped the same Acbel PSU (exept the three big ones). Before the recap pressing the power button didn't do anything. (no light, no fan movement, etc..)

After recapping the PSU , I get the +5V TRKL and te +25V standby.
If I jumpwire pin 11 the fans briefly spin. If I jumpwire pin 11 repeatedly and fast about 10 times then the PSU is alive, and all the readouts are fine.

Trying the same using the power-on button when connecting it to the motherboard doesn't work. No fan movement when I connect it to the motherboard.

any ideas?

These were (or seemed) the faulty caps on my PSU:

C21 TEAPO 3300uF 10V, my ESR meter reported: "leaked, 0,92 Ohm"
C32 LTEC 47uF 25V, ESR meter reported "35.2uF, 13.3 Ohm"
C53 LTEC 4.7uF 50V, ESR meter reported "3.9uF, 10.5 Ohm"
C45 LTEC 10uF 50V, ESR meter reported "7.1uF, >20 Ohm"

[domas]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

+25V standby?
you mean before rectifier?

or this is normal for apple computers?

[goontron]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

+25V standby?
you mean before rectifier?

or this is normal for apple computers?

there is a 24v line, but it likes to run at 23v to 25.23v which is fine since its just a backlight inverter power source (which i have seen run from 12v)

[Toasty]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

@ Didius:
- Did you do the 100/25 C43?
- What caps did you do and with what brand/series?
- +5V TRKL...? - You mean 5VSB, yes?

It sounds as though one of the startup caps is not correct. The rapid pulsing you do -evntually- makes it work. Please provide more info as requested regarding the caps you used for recap.

@ domas:
This power supply and others for the G4 series have a 25v line for the system. The voltages this one outputs are 5VSB, 3.3V, 12V, -12V, and 25V.

@ goontron:
I believe you have your systems mixed up
This PSU has 25VSB, not 24VSB. There is no backlight inverter on the G4. That's on the iMac G5 series AiO's.

T

[Didius]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

I've replaced all the caps except the 3 big ones.

Here's an overview

C29 & C16 => Panasonic FM 2200uF 6,3V
C13 => Panasonic FC 2700uF 6,3V
C59 & C60 => Panasonic FM 1000uF 10V
C21 => Panasonic FM 3300uF 10V
C10 => Panasonic FR 2200uF 16V
C8 & C32 => Panasonic FR 47uF 25V
C43 => Panasonic FR 100uF 25V
C35 => Panasonic FM 470uF 35V
C7 => Panasonic FM 220uF 35V
C41 => Panasonic FR 680uF 35V
C55, C56 & C30 => Panasonic FC 1uF 50V
C53 & C45 => Panasonic FC 10uF 50V

I mean pin 1 (+5V Trkl Standby)

[Toasty]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

Cap brand/series is okay.

Some differences -

C55, 56, 30 - I have as: 0.47/50

C53 - I have as: 4.7/50

C57 ? - I have as: 4.7/50

43 & 32 are the usual trouble caps. Try a lesser series there such as FC or PW. FR may be "too good".

T

[Didius]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

Thanks for the cap review.

About the differences.
I couldn't get a 0,47uF/50V cap at my cap store, I thought 1uF/50V would be okay?
The same for C53

I didn't recap C57, where can I find that one? Is it on the daughterboard? Should I replace those caps to?

[Agent24]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

You can't power up this Mac PSU the same way with a normal ATX. One of the lines needs a small load on it as well. I used a 15 ohm 5 watt resistor. I forget which line though. I found it on a website detailing how to convert the PSU to a benchtop supply.

But then, if it won't start in the Mac, I guess there is something else wrong anyway.

[Didius]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

I discovered something new today.

After connecting the PSU to the motherboard, i tried shorting 2 power contacts (S5) on the board. (neard the PMU reset)


The powermac booted right up. Does that mean the PSU is fine, and the power button board is toast?

[Agent24]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

The powermac booted right up. Does that mean the PSU is fine, and the power button board is toast?

That could well be the case. It's not unheard of for power\reset buttons to fail on standard PCs at least.

[Toasty]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

...or the cabling or the motherboard...

[Scruffy]

Re: Apple MDD G4 PSU (AcBel API1PC36) - Recap question

Alrighty, yet another wake-up for this thread. I re-capped my AcBel Rev. B with suitable caps I sourced locally, this was sometime around last Christmas.

Tried to power on the PSU stand-alone on the desk by shorting the power-on line, but no go. Decided to put the whole project to rest and the PSU ended up more or less disassembled in a drawer, but with brand new caps. Then I moved to Germany for work.

Fast forward until last weekend, home for Christmas, I decided to try again. Looked on this thread and noticed that one line needs a load for the PSU to actually start up, so I decided to hook it up to the G4, and whadya know - started up like a charm. Time for some OS9 nostalgia!