Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

[Miragui]

Hi all. I need some help with this PSU. There is no output to the computer no and standby voltage at all. No burn or overheating marks.
The fuse is not blown.

Where would you guys look first?

[R_J]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

What is the 16 pin ic in picture #1 lower left, half way under the black bar? that could be the standby drive ic. The voltage on the main caps is low because the pfc is not running yet likely due to being in a standby condition.

[Miragui]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

The 16 pin ic is a NCP1605BG.

[R_J]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

Do you have any voltage on pin 16 of that ic? This ic should be on the HOT side so use pin 9 for ground or (-) side of large cap for ground

[Miragui]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

There is 150V on pin 16.

[R_J]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

Is there any voltage on pin 11? If not I suspect the ic is either not working or is being shut down, Page 2 of the pdf has a partial schematic.

[Miragui]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

Pin 11 is oscillating between 7.5V and 14.5V.

[Miragui]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

I think I found something right next to the chip that doesn't look right.

W2X 25 doesn't look to healthy and the small cap next to it either.

[R_J]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

If that voltage is jumping around, that means the ic is starting up and shutting down, which means it is likely ok. and the fet it drives is also ok.
That almost looks like water damage, try cleaning that white corrosion and see if it starts up.
Transistor could be a PMBT4401

[Miragui]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

So I should find out why it's shutting down right?

[Miragui]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

I cleaned and resoldered the corroded pins but it's still doing the same.

[R_J]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

That ic drives the fet, which switches the dc across the transformer, the transformer has at least 2 secondaries. one that feeds back to supply Vcc for the ic,(pin11). since that voltage is there but pulsing, means the circuit is trying to operate. so on the other side (secondary) of the transformer you should have a diode that supplies the standby voltage. If there is a short on the secondary, that would load the standby circuit causing it to oscilate.

If cleaning did'nt help, check the transistor to see if it is ok, It should be a npn

[Miragui]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

The transistor is ok.

[R_J]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

I'm just not that familiar with this apple power supply, I could'nt even find a pinout for it
are you sure there are no voltages on any of the plugs? It almost seems like there should be a power supply on pin somwhere.
There is a small electrolytic cap in that area, did you check it?
What are the 3, 8 pin ic numbers?
Red =
White =
Blue =

[isolutionmac]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

Hi R J verify or substitute the bridge refiner on secundary power supply.

[R_J]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

Hi R J verify or substitute the bridge refiner on secundary power supply.

Its not me working on this. I eat Apples I don't repair them.

[Miragui]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

Here are the ic numbers

1=DA501A PZZB
2=SRK-2000D 6B323
3=AP4310 AM-G1 314J18

I checked the small electrolytic cap and it's fine.

[Miragui]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

Hi R J verify or substitute the bridge refiner on secundary power supply.

Hi isolutionmac can you show me what part is the bridge refiner please? Thank you.

[R_J]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

I think he ment bridge rectifier, if it was bad IE: shorted, it would blow the main fuse, The fact that you have 160 volts on the main filters means the bridge rectifier is ok
I thought maybe knowing those 3, 8-pin ic's would help, but it did'nt so far.

There are 2 diodes mounted to the heatsink near the output, they should be checked, they are likely 2 diodes in a single package with the center pin common.

There are other diodes on that board that should be checked to make sure none are shorted. Having only a picture and the fack that the board is double sided makes it hard to trace.

[einst]

Re: Need some help diagnosing iMac 21.5 A1418 Delta ADP-185BF T PSU

non si trova lo schema dello alimentatore?

grazie