iMac 24 PSU LITEON PA-3241-02A1 250W

[Toasty]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

What type/brand caps did you use for replacements? (C214 & C215)

>>I've heated all capacitors with a hairdryer.. No effect, so i dont think a capacitor is defective.<<

--> Not a method to verify a capacitor. You need an ESR meter. <--

All the output caps need replaced. All are in parallel with at least one other so not possible to accurately tell which are failed. They all are from known problem series from United-Chemicon KZH & KZE in that manufacturing time frame. Multiple failures seen in my experience. Later versions are fine.

Qty - Value - Replace with (match sizes)
3 - 2200/16 - UCC KY
1 - 2200/16 - UCC KZH
2 - 470/50 - MAT FM

Inspect the chip side of the board for an burned/open resistor. Looking at 2x1mm and 3x2mm chip resistors, you'll need a jeweler's loupe and a good strong light.

With an LED glowing, apparently you have standby voltage. Review post 67 above and see if you can get this working while disconnected from the motherboard.

T

[koektrommeltje]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

What type/brand caps did you use for replacements? (C214 & C215)

>>I've heated all capacitors with a hairdryer.. No effect, so i dont think a capacitor is defective.<<

--> Not a method to verify a capacitor. You need an ESR meter. <--

I know, but most of the time a good manner to get an idea. Higher temperature = lowering the ESR and bringing back capacitance for some time.. But not 100% reliable.

I replaced C214 und C215 with 16V of 25V low esr capacitors, Ltec RXK',s i'm using on a regular base for repairing. Will do, other devices repaired with those capacitors are working again for multiple years. Don't see any problem in that, they're OK.

I have an ESR meter, but need to desolder some of the capacitors to check them. Not yet done.

All the output caps need replaced. All are in parallel with at least one other so not possible to accurately tell which are failed. They all are from known problem series from United-Chemicon KZH & KZE in that manufacturing time frame. Multiple failures seen in my experience. Later versions are fine.

Qty - Value - Replace with (match sizes)
3 - 2200/16 - UCC KY
1 - 2200/16 - UCC KZH
2 - 470/50 - MAT FM

Inspect the chip side of the board for an burned/open resistor. Looking at 2x1mm and 3x2mm chip resistors, you'll need a jeweler's loupe and a good strong light.

With an LED glowing, apparently you have standby voltage. Review post 67 above and see if you can get this working while disconnected from the motherboard.

T

Haven't checked the other capacitors, but will do. Have most of the capacitor on stock, so will replace them or measure them. Never seen any failed chemicons by the way..have been using KZE's for years. Green ones..these are brown.

Resistors i will measure.. but they don't seem burned.

[koektrommeltje]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

Can't check the capacitors with my ESR-meter.. Seems like it's on the end of it's life. It's giving strange values.. (Just like some weeks ago)

Dont have 50V/470uf.. 35V is to less i assume?

[Toasty]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

Yes, 35V is too much under voltage. 560/50 perhaps? Even 680/50 as temporary.

Fix the ESR meter...

Ltec/Lelon are the bane of many problems from before and are ROS (Replace On Sight) for me. Can't speak to their current production, however.

A visual is all that's needed on resistors. As long as you can read the number, they are typically fine.

T

[koektrommeltje]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

The resistors seem to be OK. Measered the most of them and they all seem to be ok. All numbers can be read.

For the ESR-meter; i've sent an email to Russia (it's an ESR Micro from Mike Klykov) to buy two new ones. It really behaving strange, even though i've changed the batteries for new ones I see the battery indicaties switching from 3 stripes to 1, giving really strange worths, calibrating suddenly, etc.. Don't know what's wrong with it, and too bad, i don't know how to repair it.

Don't have 50V capicators, so i have to buy new capacitors first, even though i dont think it's te capacitors. But swapping them won't do any bad and since it's allready 9 years old or so, it's not a bad idea.

Later more.. Will try it with the 1k Ohn resistor (or, 940Ohm, since i dont have a 1K )
I appreciate your help

[Toasty]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

Yeah, I tried his unit too as a comparison to my Anatek Blue ESR meter. Had issues in about a month. I think I tested a small charged cap at some point. It now resides in a junk box around here... The Anatek Blue is only $20 more and a solid performer.

You can also get the DIY kit Blue ESR Meter Kit which is only $5 more than Mike's.

T

[LuisJCC]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

Are you testing this on the bench, or are you testing it in the machine?

Did the fuse blow when you plugged it in or when you turned it on?

Looks like you used a glass body fuse...? Did it just open (overload), or did it blow violently and leave black and silver inside the glass (dead short)?

Check with an ohmmeter across the mains power leads to see if you have a short. One leg is Common (blue), the other is Hot (brown) and goes through the fuse. Use the Common and test on opposite (circuit) side of fuse. Remember to reverse the leads when testing as some defects show on the opposite polarity.

The "usual suspects" here are the bridge rectifier, switching triacs, or one or both of the mains caps.

T

Ok master, thanks for all. About the question if I´m testing the PS in bench or computer, I don´t have the computer in the laboratory, I´m working with it on the bench.

Other, I´m using this class of fuse because is impossible to find the original (same like original) in this moment... what is the different between both?

I've checked the comon and hot and don´t have shorcut, but... testing and testing arrived to a 6R165P of Infineon... and it has shorcut in all his legs. It is near of the bridge rectifier with the metal cooler. I changed for a new one, but... is it ok if we have shorcut between legs 1 and 2 (gate and drain)?... when we test with multimeter, have "beep" between 1 and 2 of the mosfet...

I´m afraid to connect to the 220v and check it...

[Toasty]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

Make sure you are using a Digital Multimeter (DMM) in Diode Test mode.

It sounds like the replacement 6R165P is defective. These are static sensitive, so replace it again, and test it -before- you install it in the board.

In Diode Test, mine shows no resistance between all legs, except for 2 & 3. On 2 & 3, I get 0.6Ω one way and no resistance the other.

You should also be using a incandescent lamp in series with the power when testing. Saves components, especially MOSFETS & fuses. See this post. Adjust voltage for your region (220V).

T

[LuisJCC]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

Ufffff difficult to understand (sorry for my english)...

when you say "It sounds like the replacement 6R165P is defective. These are static sensitive, so replace it again, and test it -before- you install it in the board."... what does it mean? I extract the 6R165P an check it out of the pcb, and all the legs have shortcut (1-2, 1-3, 2-3) "beeep" in diode mode... I think it´s bad, then change it for a new one.

Then you say "In Diode Test, mine shows no resistance between all legs, except for 2 & 3. On 2 & 3, I get 0.6Ω one way and no resistance the other."... you mean test the new mosfet... why? and, in the board or before fix it.

[LuisJCC]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

thanks for the bulb suggest ¡¡ cool. Last question, how can I try to switch on the PSU an check the volts in pinout? Do you know where can I check volts in the pinout?

Thanks master ¡¡¡

[LuisJCC]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

Hi ¡¡¡ I tested all the diodes of the PCB and change two diodes which have shortcut (BEEP¡), then I fix two new ones and... still shortcut. I tested the diodes out of the board and was OK...





what do you think about this? Thanks for all ¡¡¡

[Toasty]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

I've attached your photos to the thread. Using "photo-sharing" services is not advisable. If they should delete the photos or go out of business, the next person looking at the thread will not see your pictures.

Use the "Go Advanced" button anytime you have a picture or file to attach. When in "Advanced" mode, use the "Manage Attachments" button, lower down on the page, to do so.

By using this method, you photos & documents become a permanent part of the forums.

T

[Toasty]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

re: your Post 89 questions -

1) You said in Post 87: >> I changed for a new one, but... is it ok if we have shorcut between legs 1 and 2 (gate and drain)?... when we test with multimeter, have "beep" between 1 and 2 of the mosfet... <<

to which I replied: >>It sounds like the replacement 6R165P is defective. These are static sensitive, so replace it again, and test it -before- you install it in the board. <<

Yes, test it BEFORE you install it to verify you don't have a bad one. See this YouTube video on testing a MOSFET.

Regarding your diode replacements: Those diodes on my unit read "shorted" as you indicate, but that is because they are "in circuit" and are affected by other components, such as the transformer. They are not shorted. Make sure you replace them correctly with the cathode mark (band / line) properly oriented. Pic 1 it is at the top, Pic 2 it is at the bottom. I marked the attached pictures for reference.

Turning on these power supplies: They are always "on", but require a small load to make them turn on completely. The use of a small incandescent automotive style bulb (marker lamp or interior bulb) across the 12V output will cause them to come on fully.

In your picture #1 - The 2nd transistor above and to the right of the resistor marked R0102, and just to the right of the tan capacitor, seems to have a hole in it. Is it just the picture or angle? Or is there a hole in the device? Yellow Arrow

There also seems to be a piece of solder between pins 2 & 3 of the 6R165P...? Red Arrow

T

[LuisJCC]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

OK, thanks ¡¡¡ I didn´t know it. And about the theme...

*Sorry, our posts cross them.

[LuisJCC]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

Hi Master, I prefer to answer you quoting

re: your Post 89 questions -

1) You said in Post 87: >> I changed for a new one, but... is it ok if we have shorcut between legs 1 and 2 (gate and drain)?... when we test with multimeter, have "beep" between 1 and 2 of the mosfet... <<

to which I replied: >>It sounds like the replacement 6R165P is defective. These are static sensitive, so replace it again, and test it -before- you install it in the board. <<

Yes, test it BEFORE you install it to verify you don't have a bad one. See this YouTube video on testing a MOSFET.

OK master, I´ve extracted the mosfet of the pcb and checked it (same the video you link me), and the mosfet (out of the pcb) is OK. It isn´t shorted between source and drain, and using the dischard mode, is ok too. If I try in the holes (pads) of the pcb where the mosfet is fixed, is shorted the holes where insert pins of gate and drain (1 and 2)... ¿? I didn´t check it before fix the new one (remember old mosfet was completely shorted)

Regarding your diode replacements: Those diodes on my unit read "shorted" as you indicate, but that is because they are "in circuit" and are affected by other components, such as the transformer. They are not shorted. Make sure you replace them correctly with the cathode mark (band / line) properly oriented. Pic 1 it is at the top, Pic 2 it is at the bottom. I marked the attached pictures for reference.

OK, thanks for the info. I checked the position of the two new diodes, and it´s ok, cathode is in the same position of the "star" marked in pcb.

Turning on these power supplies: They are always "on", but require a small load to make them turn on completely. The use of a small incandescent automotive style bulb (marker lamp or interior bulb) across the 12V output will cause them to come on fully.

Ok, I would like to connect and try to turn on: where can I connect the 12v bulb? I have in home old bulbs of this class. I will try connecting the 220v bulb in series (no break components) and then, where can I connect the 12v bulb? And... imagine that the bulb light on... does it mean it works fine? Do you know thw volt which we have in pinout pins?

In your picture #1 - The 2nd transistor above and to the right of the resistor marked R0102, and just to the right of the tan capacitor, seems to have a hole in it. Is it just the picture or angle? Or is there a hole in the device? Yellow Arrow

There also seems to be a piece of solder between pins 2 & 3 of the 6R165P...? Red Arrow

T

It´s perspetive and shadows. It´s OK hehehe.

Thanks master.

[Toasty]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

Please refer to the attached picture and 2 PDF's.

If you have a short between 1 & 2 (gate & drain pads) with the MOSFET -removed-, then there is a SERIOUS issue with the board.

There is really no way for a short between 1 & 2 to happen. The Gate (1) gets it's drive from the IC TEA1750T, pin 13, FBDRIVER. It's a direct connection with just that 1 diode and 0Ω jumper between it and the MOSFET gate.

Please confirm the short on the board without the MOSFET -IS- between 1 & 2.

T

[LuisJCC]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

Please refer to the attached picture and 2 PDF's.

If you have a short between 1 & 2 (gate & drain pads) with the MOSFET -removed-, then there is a SERIOUS issue with the board.

I know ...

There is really no way for a short between 1 & 2 to happen. The Gate (1) gets it's drive from the IC TEA1750T, pin 13, FBDRIVER. It's a direct connection with just that 1 diode and 0Ω jumper between it and the MOSFET gate.

Please confirm the short on the board without the MOSFET -IS- between 1 & 2.

T

Yes, the short is between 1 and 2, I just check one more time. What do you think?

NOTE: I´m checking the circuits you draw in green which run 1 and 2 and It´s correctly: could be the TEA1750T ??? A short between pin 13 and 16 ??? It´s the only option, I think...

NOTE 2: NEWS ¡¡¡ NEWS ¡¡¡

I´ve tried to extract the TEA1750T because all the "checks" in the circuit between 1 and 2 is clean (no shorts), and I thought "if I extract the TEA.. maybe the short is the IC"... YES ¡¡ There is a short between pin 13 and 16 in the IC and reading the datasheet... it has different functions and shouldn´t be in short...

What do you think about this? I check the IC out of the board and short between 13 and 16 ... new one?

Thanks ¡¡ Thanks ¡¡

[Toasty]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

Excellent! Yes, that's what I would have done next. It's the only place a short could be between those pins. That's why I drew the trace lines on the picture and sent the IC electrical PDF. Once you examine the circuits they show, it was the only logical explanation.

You figured it out, and that's great!

I hope you can acquire a new one. If you need help finding one, use this link to the Find Chips website - findchips.com .

Good Job!

T

[koektrommeltje]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

To come back on my defective power supply:

according to the post 67 of "Toasty"

[koektrommeltje]

Re: iMac 24 PSU LITEON PA-3241-02A1 250W

I connected pins 1 and 4 with a 1k resistor. Now the output is as follows:

pins 2, 8, 9, 10 give 12.25V. Others all 0

over pin 1 and 4 is 0.5V. No display or motherboard was connected.

I think this is ok and will mean something in the start circuit is defective or the condensator is defective and gives too low energy for starting up?

(with motherboard and LCD connected before the following things happened: diagnostic led 1 was on and stayed on,
leds 2 and 3 come on, the fan turns 5-10deegrees, the diagnostic leds 2 and 3 fall out, I heard a click, 2and 3 come on, fan turns 5-10degrees and stop, 2 ad 3 fall out ,
and so on and so on.)

After rechecking output voltages, something went wrong and the fuse did blow. I did accidently connect 2 pins or a pin and something directly next to it with my multi-meter. I was measuring at the back of the power supply at that moment.

Rectifier and the tested diodes are still ok. No visible damage can be seen anywhere. I go buy another fuse and retry.

Any suggestions about what can be the defective component? And what can be damaged after the damaged (before and after the shortcut)?