Power Mac G4 Mdd Acbel power supply (not Samsung)

[falcontech]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

so maybe it is shutting down from it thinking it is a over / under voltage condition?

I don't know but when I try to turn it on the only thing powered is the motherboard and the video card

[CapLeaker]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

Don’t try the PSU in your computer. Just force it on manually. If the diodes and fets aren’t shorted on that heat sink, that switching them won’t make a difference. Change C43.

[falcontech]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

ok in a while I will try to change that capacitor

[CapLeaker]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

In general: Capacitors near a heat sink are always suspect!

[falcontech]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

I inverted the diodes with the heatsink and they work on the other power supply, now I change the only two capacitors that I had no substitute and let you know let's cross our fingers

[falcontech]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

nothing to do, same story, now I'm trying to reverse the transformers because I'm really getting angry

[CapLeaker]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

Hmm... I did figure that switching the diodes on the heat sink won't help. So that capacitor didn't help either. As long as the transformer windings measure low resistance on both sides (primary and secondary), things are good.
There is still a possibility, that one of the Mosfet's like Q1 or Q4 isn't switching. For that you need to check the Mosfet and the whole gate drive circuit. Could be a gate resistor gone high or open, or no output on the gate drive IC. No Vcc to the Gate Drive IC... etc. Problem is, that you have to be really careful working on the primary mains circuitry.

[falcontech]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

Ok now I'm reversing the transformers, I have already dismantled them, I understand which are q1 and q4 and I can control them, I have not understood what are the other components you say, if you make me understand with the map I sent you I would be grateful
thanks

[falcontech]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

I inverted the transformers and that's not the problem, on the one hand I'm happy because I think it's the only component that I wouldn't have found to replace it ... ok I await your instructions

[R_J]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

the daughter card should take care of the fans I don't think that's the problem, what type of power supply do you say ac or dc? and how many volts?

The daughter card does more than fan control. There is a WT7515, this ic monitors the output voltages, (12,5,3.3) and provides protection as well as a power good signal to the motherboard.

[CapLeaker]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

O.k. lets make it easy. Try switching heat sink 1, same way you did with heat sink 2 from the good PSU to the bad PSU.
Look at your picture number 4, there is a green vertical circuit board and next to it is a small capacitor, change both.
I cant see under heat sink 1, where the transformers are. The same area is covered on the bottom picture.

[CapLeaker]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

thats what i was thinking first place that so called fan control board on the secondary. It has too much stuff on it just for a fan control.

[falcontech]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

Ok guys tomorrow I will do all these tests, I will keep you updated ... I am going crazy, I have already dismantled one of the heatsinks on the primary and it is really a mess for the heatsink anchors tomorrow, I checked the mosfets with the tester and they look good

[falcontech]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

can you recommend an equivalent of the WT7515 I looked at Google but I saw that no distributor appeared in the search that had it, I did a quick search and I didn't apply much

[CapLeaker]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

Don’t make yourself go crazy... take a breather, if you have to. A step at a time.

[falcontech]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

In a few hours I will do the other tests that you have recommended, in the meantime can you tell me what I can replace (If it were needed) that wt7515?

[CapLeaker]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

switch out the whole board.

[falcontech]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

I did not understand sorry

[falcontech]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

before putting the heatsink back I have to check something else

[falcontech]

Re: Power Mac G4 Mdd Acbel power supply (not Samsung)

Guys then I'll update you, we managed to get it turned on, I didn't change the daughter card I only inverted the heatsink with the mosfets and replaced that small capacitor that Caps told me and now they both work ... Thanks for everything and for your patience! !! I have to repair a common atx, can I write to you here if I have problems or have to open another thread?