Newbie - Imac 24 - Liteon PSU - no power at all

[StraitNet]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

TELVM..thank you very much, that is a big help. Now once I can function tonight I have some more research and reading to do

Hope you had a happy T-day

[StraitNet]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

So haven;t had much time in pat few days to read up on things..but did get a light bulb in soldered in place of the 5 amp fuse so now I can ass power to the board and check for heat or wait for something to smoke.

Any idea how long I should plug this in for this kind of poor mans test?

And any tips on what to feel or even check would be great. I don't want to touch something that will give me a zap so haven't been playing with this setup until I learn more.

Thank you.

[dyoodekz]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

We have the same power supply, and maybe the same issue. I haven't tested it yet but will do it later. I don't see any burnt FETS or bulged Caps.

What is the model no. of the fuse? Ebay link?

Let's help each other.

Thanks.

[dyoodekz]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

So haven;t had much time in pat few days to read up on things..but did get a light bulb in soldered in place of the 5 amp fuse so now I can ass power to the board and check for heat or wait for something to smoke.

Any idea how long I should plug this in for this kind of poor mans test?

And any tips on what to feel or even check would be great. I don't want to touch something that will give me a zap so haven't been playing with this setup until I learn more.

Thank you.

We have the same power supply, and maybe the same issue. I haven't tested it yet but will do it later. I don't see any burnt FETS or bulged Caps.

What is the model no. of the fuse? Ebay link?

Let's help each other.

Thanks.

[dyoodekz]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

So haven;t had much time in pat few days to read up on things..but did get a light bulb in soldered in place of the 5 amp fuse so now I can ass power to the board and check for heat or wait for something to smoke.

Any idea how long I should plug this in for this kind of poor mans test?

And any tips on what to feel or even check would be great. I don't want to touch something that will give me a zap so haven't been playing with this setup until I learn more.

Thank you.

I just confirmed that the fuse of my PSU is also blown. Can I go lower or higher than 5A fuse? 5A will be coming from Taiwan and I don't want to wait that long. I see 2A and 6.2A fuse that is available in the US.

[budm]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

@DYOODEKZ:
Pictures of your fuse?
http://www.mouser.com/ProductDetail/...ndH1v%252bE%3d

[dyoodekz]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

@DYOODEKZ:
Pictures of your fuse?
http://www.mouser.com/ProductDetail/...ndH1v%252bE%3d

Attached is the fuse. Thanks for the link. I'll drop by our local electronics store before I order online. Hope they have this part. Thanks again.

[budm]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

That one from mouser should work, but 100% you do have shorted circuits some where on the board so you need to really find out where instead of keep blowing the new fuse.
Put 120V 75W lamp in series with the power supply or build something like this:
https://www.badcaps.net/forum/showpo...&postcount=112

[dyoodekz]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

That one from mouser should work, but 100% you do have shorted circuits some where on the board so you need to really find out where instead of keep blowing the new fuse.
Put 120V 75W lamp in series with the power supply or build something like this:
https://www.badcaps.net/forum/showpo...&postcount=112

Thanks for that info. The shorted circuit is in the PSU board only, or is it possible the other parts(mobo, vidcard, etc.) shorts the PSU? or just focus on the PSU. Thanks.

[budm]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

You can test the power supply board by itself without having other boards connected, there is at least one standby power supply on that board which runs 24/7 the minute you supply AC to the board.

[dyoodekz]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

You can test the power supply board by itself without having other boards connected, there is at least one standby power supply on that board which runs 24/7 the minute you supply AC to the board.

Did some testing last night and found that all of the pins of the 6R165P transistor are all shorted. I did an inboard testing, will removed it later to confirm. I need help with equivalent transistor that I can use and available in the US. Thanks.

[dyoodekz]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

Confirmed, the 6R165P and fuse are bad in my PSU. Ordered parts and will update next week. Thanks for the help.

[budm]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

You have to be careful, most of the time when thw MOSFET shorted out it will damaged the IC that drive the signal to the GATE pin of the MOSFET, so when you put in the new MOSFET it will cause the MOSFET to blow up if the Gate drive pin is stuck high and make the MOSFET to be fully on instead of switching the MOSFET on and off at high frequency.

[dyoodekz]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

You have to be careful, most of the time when thw MOSFET shorted out it will damaged the IC that drive the signal to the GATE pin of the MOSFET, so when you put in the new MOSFET it will cause the MOSFET to blow up if the Gate drive pin is stuck high and make the MOSFET to be fully on instead of switching the MOSFET on and off at high frequency.

Update: Replaced the fuse and the MOSFET. Tested, the fuse blew but the mosfet is still OK. now what? I need help what to check? I hope I don't have any issues with the IC's. Thanks.

[Jamieson]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

Similar situation here -- bought a non-working iMac cheap.

PSU is Liteon PA-3241-02A2 REV. A

Blown 5A input fuse on the PSU. Caps look OK. None of the MOSFET pins are shorted. Diodes and bridge rectifier test OK in circuit.

Any suggestions for other things to check?

Since there are no obvious problem components, I'll try putting in a new 5A slow blow fuse and power it up on the bench. Will check for 12V standby power... and check for magic smoke.

jamieson

[budm]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

Update: Replaced the fuse and the MOSFET. Tested, the fuse blew but the mosfet is still OK. now what? I need help what to check? I hope I don't have any issues with the IC's. Thanks.

The bridge rectifier test OK? The new MOSFET could have blown open circuit. That is one reson I do not like to put in new MOSFET unless I am 100% sure the IC is good.
I would put 75W lamp in series with power supply so you do not keep blowing up parts. You can remove the MOSFET, then check the resistance on the two legs of the main filter cap to see if it shows low resistance (load side of the bridge rectifier), than check between the ~ of the rectifier (input side) to see if it shows low resistance.

[Jamieson]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

sorry for the cross posting...

updates are in this thread:
https://www.badcaps.net/forum/showth...t=38233&page=2

[Mrmullad]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

Hi all new member here
Sorry if this is posted in wrong place but as I cannot start new post (being new member) I have no other option so please feel free to move if needed.
I have a 2009 A1225 Apple Imac 24" and the PSU went faulty I found a brand new one from China when it arrived I fitted it and all worked fine for about 4 hours then a loud bang and the trip went out when I removed it I found the fuse had blown , not sure where to go now this unit was brand new so to me this points to another part drawing to much power rather than the PSU but as I am no electronic wiz I am asking the experts.
PS the old PSU had no obvious signs even the fuse was ok.
Thanks in advance Dell

[Toasty]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

@Mrmullad - New from China means "it's been sitting here for 5 years with the bad caps slowly dying". We sell cheeeep!

Will need pics of the board, top and bottom. CLEAR images please and large enough so grandpa can see it -without- glasses.

>>not sure where to go now this unit was brand new so to me this points to another part drawing to much power rather than the PSU<<

No, just bad caps on the power supply, otherwise the fuse would have blown or the unit just would not start.

Please report and confirm that the make and model number are the same as this thread.

T

[Mrmullad]

Re: Newbie - Imac 24 - Liteon PSU - no power at all

Thanks toasty for your prompt reply
Please see attached pics