IMAC 24 PSU Bad Caps replacement

[bosscharles]

Re: IMAC 24 PSU Bad Caps replacement

Oops sorry, yes that is what I meant to say uf readings were very low.....

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

[QUOTE=bosscharles;467405]>>...I'm not sure what you mean by load it with a lamp or two? or how I would go about doing this?<<

See Post 94 for an explanation. Those bulbs across the output when out of computer. That way you can see if it runs properly on the bench; the lamps come on when you plug it in. If so and it won't start in the computer, the computer is the problem, not the PSU.

T

[bosscharles]

Re: IMAC 24 PSU Bad Caps replacement

I've actually got two white imac 24's. I'll swap the psu and post results.... If it still takes 10- 15 seconds we'll know it's a psu gremlin....

[bosscharles]

Re: IMAC 24 PSU Bad Caps replacement

Same happened on the other imac 24 so it's something in the psu..... no biggie

[BadCapCop]

Re: IMAC 24 PSU Bad Caps replacement

When i plug in the power cord i hear a high pitch squeal coming from the power supply. The diagnose led lights only light on led #1. When i press the power button led #2 and #3 flash then everything shuts down, then no lights are present.

Exactly my experience yesterday.
No solution yet.

BCC

[stj]

Re: IMAC 24 PSU Bad Caps replacement

does anybody actually look at the boards they work on?

the acbel foto in the start of the thread had loads of cracked solder joints including on the opto.

[mveplus]

Re: IMAC 24 PSU Bad Caps replacement

Hello guys,

I found this forum and red all posts about this PSU!
Because I was looking for more clues and Google brought me here.

PSU details: Acbel Polytech Inc., Model No: API5ST06 , Apple P/N:614-0402, Input: 100-240V, Output: 12V / 10.3A, 24V / 4.0A, ID:291G , Date code: 0717 Rev.A

A year and half ago a friend brought to me iMac 24-inch (MA456LL) Late 2006, because it was dead. I found out the problem is it's PSU and more specifically the Caps in the 12V/24V rail, changed these with KY, WX, the PSU started working again and my friend was happy! But after a few weeks he called me again and it was the same PSU problem but this time no bad Caps, changing the caps did not help! I did not have much time back then so I got the power wires out and connected external PSU,made from what I have available in my boxes ( Old Dell 20V PSU for the screen and old computer ATX PSU) iMac still works fine, but this bugging me.... a lot...

So I was happy to find this forum and I can see I'm not alone , I found some very useful info here.

About the "the cold joints" this was the first thing I looked the second time when this PSU came in and re-flow hot air and resolder all majoir IC and bad looking solder joints.

Original PSU now still works! But when I load it over 3 Amps, no matter where 12V or 24V rail the overload protection kicks in and it shut itself down. So It can't power iMac.

So far I followed some directions found here and I changed again all CAPS on the secondary side. Including TL431. And C32 & C29 in primary side. Checked all Transistors, Diods, (Zeners), Resistors, i.e. some I needed to unsolder to make sure they have proper readings. R83 is a bit smoked around but has proper readings ~470 Ohms, according what i red here.
To be honest I did rotate VR1 in the secondary side - which is for fine tuning the output voltage ( affects both 12V and 24V), but I left it as it was. Hoping this will change something...

So PSU is working but can't provide full load. Unfortunately here I don't have Scope and "I'm blind", the only equipment I have available is Multimeter UNI-T UT61E and LCR Meter UT612.
I hope to get a Scope in January but till then if anyone have some thoughts about it will be very helpful!

Thank you!

[stj]

Re: IMAC 24 PSU Bad Caps replacement

work out how it senses the load.

[mveplus]

Re: IMAC 24 PSU Bad Caps replacement

work out how it senses the load.

Thanks for the TIP, will look closer and inspect the load protection circuit.

[budm]

Re: IMAC 24 PSU Bad Caps replacement

You should look up the spec sheet of the SMPS IC to get the application notes n how it is used, it will give you some ideas on how your power supply works.
Good clear pictures of both sides YOUR board?

[mkinn]

Re: IMAC 24" PSU #614-0387 - Bad Caps replacement

Power supply 614-0387
When it gets hot, you have to unplug it to get it to start up again.
When cool, it always starts up and runs fine. Sometimes if I leave it on for a few days, it will shut off by itself.

I know these power supplies are cheap on ebay, but I'd like to know if it's an easy fix.
I can buy these imac's CHEAP and would like to fix them for a profit.

Usually, it's the startup caps, C131, 132 - 33uf 35V 105° green Taicon, but these check fine, .5 ESR, most of my other new stock are at 2 ohms or worse.
I think these are low ESR caps. I can't find any other caps that check even slightly bad, and all look fine, no leakage on the leads or swelling of the case.

Please recommend Mfg. Types and sources for parts if you know about this problem.

[stj]

Re: IMAC 24 PSU Bad Caps replacement

caps improve when warm - it's not a cap issue. (not electrolytics anyway)

check the soldering wih a magnifier

[Philip43]

Re: IMAC 24 PSU Bad Caps replacement

Hi guys!
I'm new to this too, so please go easy!!
I have an iMac Intel core 2 duo, with the 614-0387 power supply. It's faulty, in that when powered on it works ok, but after about 5 mins, the computer hangs and requires a restart. When I do restart, the computer hangs after a shorter period of time, and after restart, the hang happens even sooner. I'm assuming that the capacitors are bad, even though there is no visible damage. No bulging, and no leaks. Do capacitors always display these symptoms when bad, or is it possible that they could be bad without displaying these symptoms? Thanks for your help.

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

Perfectly good -looking- caps can be completely weak/bad/open.

Consider that you could have an issue with the motherboard.

T

[Philip43]

Re: IMAC 24 PSU Bad Caps replacement

Perfectly good -looking- caps can be completely weak/bad/open.

Consider that you could have an issue with the motherboard.

T

Thanks for that Toasty!!
I have checked the voltage outputs on the PSB, and only 3 are giving any readings. There are 12 in total. Of these, 2 readings are 1.2v, and one of 4v. Is it safe to say the caps are shot, even though they look fine??

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

??? >>There are 12 in total.<< ???

I only count 8 output pins. This is the Delta SADP-220AFB version, correct?

There are 2 output voltages, 12V & 24V.

Are you bench testing this, or in the machine?

Low outputs such as those lead me to believe you don't have a 12V load attached. When bench testing, you have to apply a small load to the 12V to get this to come on. Usually a 194 bulb (auto marker lamp) or equivalent will do.

T

[Philip43]

Re: IMAC 24 PSU Bad Caps replacement

??? >>There are 12 in total.<< ???

I only count 8 output pins. This is the Delta SADP-220AFB version, correct?

There are 2 output voltages, 12V & 24V.

Are you bench testing this, or in the machine?

Low outputs such as those lead me to believe you don't have a 12V load attached. When bench testing, you have to apply a small load to the 12V to get this to come on. Usually a 194 bulb (auto marker lamp) or equivalent will do.

T

There are 8 output pins on the board, but I checked them from the attached lead which has a further 4 for the HD power. I also checked from the 8 pinout connection, both tests carried out in the machine powered up.

I have just checked the PSB caps with a multimeter, out of the machine. 3 appear good, but 11 are reading down to zero.

[juicer]

Re: IMAC 24 PSU Bad Caps replacement

In case anyone is interested, I had a 614-0402 power supply that was also suffering from swelling/ruptured caps. I replaced all 7 caps with the following:

C4, C2? (next to C4)
original: 1500uF 16V, LTEC LXY
replacement: EEUFR1C152 panasonic, element14 1800639

C44, C45
original: 1000uF 16V, LTEC LXY
replacement: EEUFR1C102 panasonic, element14 1800637

C46
original: 680uF 16V, LTEC LXY
replacement: EEUFR1C681 panasonic, element14 1800636

C55
original: 220uF 35V, LTEC LZG
replacement: EEUFR1V221 panasonic, element14 2217565

C39
original: 1000uF 35V, LTEC LZG
replacement: EEUFR1V102 panasonic, element14 1800671

But the supply would still not start. The PFC appeared to be working (gate drive pulses to fet). The NCP1381 had a supply voltage on it when measured with a meter. R83 was toasty but still measured the correct 475R.

Anyways looking into the supply to the NCP1381 with a scope, and lots of drop outs (below 10V which I think is the under voltage lock out). So traced this back to a mains resistor diode fed capacitor supply that was faulty. It is C32 47uF 35V LTEC, replacing this brought the PSU up but then it shut down. Next to C32 is C33, the same cap but a different rail, it tool was also faulty. Replacing this cap also returned the power supply to normal operation. The two caps are located under a heatsink near the fet for the PFC circuit. They were both covered with lots of grey silicone.

Hope this might help someone else.

Same here. Replaced the 5 swollen caps first and didn't solve the problem. Followed the above directions for replacing C32 and C33 (didn't appear damaged or swollen) and all is well.
Thanks @2lostkiwis for the tip.

[Fundy21]

Re: IMAC 24 PSU Bad Caps replacement

Hi!

You would not be able to tell it what would be his accurate type how it "ic31"-nek,or since it would be possible to substitute?