Apple TV Dead Psu

[caphair]

I have an Apple TV 3 with no output voltages from the psu.

This Psu is very tightly packed and seems impossible to troubleshoot but I would like to fix it if I can.

I've included pics of top and bottom in two different posts because my phone only allows one upload per post for some reason as I'm not on a PC.

I measure 54v on one end of the fuse on the hot side with negative probe on - of the capacitor on hot side.

[caphair]

Re: Apple TV Dead Psu

And the bottom side

[budm]

Re: Apple TV Dead Psu

You can start by checking the DCV between the two legs of those two black electolytics can laying on their sides in the hot side of the circuit to see if you do have Voltage on them.
That red rectangular box part hanging off the board looks to be the main AC fuse.

[caphair]

Re: Apple TV Dead Psu

Yes there's 163v and that's also fed into ic31

Then with black probe on negative of hot side and + probe on ic33 I see 3.7v and 2.2v on ic32. I originally thought those were on the secondary side but don't get a reading off them with ground on cold side

[budm]

Re: Apple TV Dead Psu

That unit has 3 OPTOs, 1 on the top side and 2 (IC32, IC33) so one of them is for Voltage regulation and other 2 are probably for turning on the rest of the power supplies.
What DCV and resistance do you get between the two legs of those two white electrolytics caps in the cold side?
You also check some of the Diodes on the cold side?

[caphair]

Re: Apple TV Dead Psu

On both capacitors I get .480 ohms one way and .880 ohms the other. And 0vdc across both

[budm]

Re: Apple TV Dead Psu

On both capacitors I get .480 ohms one way and .880 ohms the other. And 0vdc across both

<1 Ohms? that is not good. I would check out the rectifier diodes.

[caphair]

Re: Apple TV Dead Psu

Oops the decimal was on the meter so 480-880 ohms on both

[budm]

Re: Apple TV Dead Psu

Oops the decimal was on the meter so 480-880 ohms on both

OK, that is better, probably bleeding resistors reading.

[budm]

Re: Apple TV Dead Psu

Are you able to get the P/N of the SMPS IC 3?

[caphair]

Re: Apple TV Dead Psu

Also no voltage out of the packaged diode on cold side. Would the anode or cathode of diode be connected to positive of capacitor. Cathode right?

Here's IC3 is the middle number the part #?

[caphair]

Re: Apple TV Dead Psu

Actually pins 1 and 2 of the opto on top side of the board measures 0ohms both ways. Would this be the problem? All 3 optos are same part #'s EL3H7

[budm]

Re: Apple TV Dead Psu

Actually pins 1 and 2 of the opto on top side of the board measures 0ohms both ways. Would this be the problem? All 3 optos are same part #'s EL3H7

No it should not show 0 Ohm.

[caphair]

Re: Apple TV Dead Psu

If that's shorted what are chances other components in line are? There are smd components under the diodes/transformer that I can't get to for testing. Curious if simply replacing that opto will bring psu back to life

[budm]

Re: Apple TV Dead Psu

Pin 1 and pin 2 are for the LED inside the opto, You can try lifting one pin off the board and check the resistance between pin 1 and 2 again.

[caphair]

Re: Apple TV Dead Psu

Will do. Do you know any part stores in the US that carry these in stock? Digikey only allows minimum order of 1000 and mouser has them on back order. Found some on eBay but from China with a month delivery time

[budm]

Re: Apple TV Dead Psu

Mouser:
Stock: 933 Can Ship Immediately.

http://www.mouser.com/ProductDetail/...2bY05EmQ%3D%3D

[caphair]

Re: Apple TV Dead Psu

So got a chance to remove that opto and off board it measures fine. Does this indicate there's a short somewhere else on the primary side?

[budm]

Re: Apple TV Dead Psu

If the empty pads where the opto legs were soldered to show shorted then yes there is shorted circuit on the board that you will have to trace out to see where the connections go to.

[caphair]

Re: Apple TV Dead Psu

That's the interesting part. The empty pads show infinite resistance. Would that indicate a leaky opto or?