IMAC 24 PSU Bad Caps replacement

[bottleneck]

Re: IMAC 24 PSU Bad Caps replacement

Thanks for replying!

So do you believe the caps look bad? I know you cant always tell by looking but im not real experienced when it comes to these. It appears that this is the information on the caps (below). my measurements appear to be different than TBI's (above) but the board numbers match what he had so I could be off a little. Please let me know if you need any more additional information. I would appreciate if someone could suggest the replacements that would be best.


680UF 16v LXY 10mm x 14mm
1000UF 16v LXY 10mm x 17mm
1500UF 16v LXY 13mm x 17mm

[bottleneck]

Update:

I just wanted to update this as I have made the repair. Thanks to Sam Sam for his reply and a somewhat confusing scour of Digi-key's website I was able to purchase these items for the previously mentioned board.

(2) P12368-ND CAP ALUM 1500UF 16V
(2) P14398-ND CAP ALUM 1000UF 16V
(1) P14396-ND CAP ALUM 680UF 16V

I was hoping to get more direction here as to which model numbers would be the best, or recommendation of items from badcaps to order. I didn't, so I just made a selection after a lot of reading. As I stated previously my experience with brand preference and series understanding is limited.

The IMac is now functioning however and am thankful for the one response I did get. The other information in this forum was helpful in this process! I hope that this could help someone else out there in a similar situation.

Thanks,

Bottleneck

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

FM & FR are just fine in this application. But I only see 5 out of 7 that could(should) be replaced...?

T

[bottleneck]

Re: IMAC 24 PSU Bad Caps replacement

Thanks for adding that,I appreciate all the helpful information on this forum! What would be the best replacement for the remaining 3?

They are:

22uf 50v LZG
220uf 35v LZG
1000uf 35v LZG

Would you use a different series than fm or fr?

[sam_sam_sam]

Re: IMAC 24 PSU Bad Caps replacement

They are:

22uf 50v LZG
220uf 35v LZG
1000uf 35v LZG

Would you use a different series than fm or fr?

I will use FR FC FM and some time these two KY KME

P15374CT-ND = 22uf 50v

P10297-ND = 220uf 35v
Size / Dimension 0.394" Dia (10.00mm)
Height - Seated (Max)
0.492" (12.50mm)

OR

P10296-ND = 220uf 35v
Size / Dimension
0.315" Dia (8.00mm)
Height - Seated (Max)
0.591" (15.00mm)



P15382CT-ND = 1000uf 35v

[bottleneck]

Re: IMAC 24 PSU Bad Caps replacement

I appreciate all of your help! I have run into another issue.

The power supply worked for a short time and then quit. I have replaced the other 3 caps as Toasty suggested and it resulted in it working again. I could hear a high pitch noise coming from a section of the psu while it was plugged in but turned off. It worked for a couple of days and then dead.

It keeps killing the 22uf 50v cap.

Any ideas??

Thank you!!

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

How do you mean "killing" it?

T

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

Are you installing it correctly, polarity-wise?

.

[ben7]

Re: IMAC 24 PSU Bad Caps replacement

So, all the caps are replaced?

It seems like the whine is coming from oscillations in the PSU circuit, which could be causing too high a voltage on that capacitor. I think the IMAC PSU's are VERY picky about the ESR of the secondary capacitors :S

[Francisco.s]

Re: IMAC 24 PSU Bad Caps replacement

So, all the caps are replaced?

It seems like the whine is coming from oscillations in the PSU circuit, which could be causing too high a voltage on that capacitor. I think the IMAC PSU's are VERY picky about the ESR of the secondary capacitors :S

Anyone has the squematic diagram for this PSU?
Thanks ind advance.

[bottleneck]

Re: IMAC 24 PSU Bad Caps replacement

I apologize for the delay in getting back to you guys and appreciate your feedback!

I have installed the caps correctly polarity wise. I am limited in understanding the theory behind cap series differences and ESR levels. I have an interest in this level of troubleshooting and read as much as time allows.

I replaced the 22uf 50v cap with the recommended P15374CT-ND panasonic it lasted about 2days then the computer wouldn't startup.

I checked the cap with a volt meter(I know its not accurate) its all i have now. I switched legs of the meter back and forth on the legs of the cap to see if it would charge and discharge. It showed no response...I would like to get a blue esr meter or any other recommended devices? I just don't have the money right now.

I then ordered 565-3341-1-ND KMG(I should have came back here with the results first). Then it worked for about a day (could hear the noise coming from the power supply when in standby. now it wont power on again. suspect the same cap not working, as it is completely quiet(dead) imac diag lights show no power from psu. Same results as before!

Any ideas?

please let me know if you would like me to clarify anything more!

Thank you!

[bottleneck]

Re: IMAC 24 PSU Bad Caps replacement

Anyone has the squematic diagram for this PSU?
Thanks ind advance.

I did email them for a schematic of this psu. I didn't receive a response and wasn't successful in finding one. From what I have read, they don't typically give them out... Any suggestions?

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

Anything of interest on the trace side of the board? No one has posted a pic of that yet.

I'm thinking a bad rectifier somewhere, passing AC to this cap.

T

[bottleneck]

Re: IMAC 24 PSU Bad Caps replacement

Anything of interest on the trace side of the board? No one has posted a pic of that yet
T

Wow! after some inpection i noticed what appeared to be an area that got hot.This is the general area i thought i heard the noise comming from on the other side though. If you look at the pictures one of which i have an arrow pointing to the componant. Is this a resistor? The numbers appear gone now, i cant make anything out.

With my meter set to ohms it reads .472 k both directions. Is this right, or is there another way to check this?

Do you have any ideas as to what to check next or what the replacement would be?

Thanks!

[mockingbird]

Re: IMAC 24 PSU Bad Caps replacement

I would not use HZ or MCZ class capacitors in a PSU... You should replace those with suitable caps and replace all the capacitos in the PSU and not just the ones that are bloated.

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

R83 is toast.

Check D9 near the cap that keeps blowing.

What is the device in the gray goop next to that cap? 3 legged, TO-92 package.

Identify (case markings) M6, M9, M10?

T

[Francisco.s]

Re: IMAC 24 PSU Bad Caps replacement

R83 is toast.

Check D9 near the cap that keeps blowing.

What is the device in the gray goop next to that cap? 3 legged, TO-92 package.

Identify (case markings) M6, M9, M10?

T

I have the same PSU, and r83 is also toast.
Meter also set to ohms, and it reads 15 kohms also both directions, and I can`t find D9 in the PCB.
This PSU (in my case) has cero voltage in its ouputs, but the mosfet (q13) has little pulses in its gate (and very narrow) and doesn`t work, probably because the pulses doesn`t reach the minimum level.
The mosfet (q2)at the PFC circuit, has good pulses and works properly.
The main problem for me, is the schematic diagram. (seems difficult to get a copy)
Your comments and suggestions would be greatly appreciated.

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

D9 is right above the lightning symbol on the trace side. It is directed at bottleneck because of its proximity to the cap that self destructs.

Schematics are proprietary. Not available.

Caps replaced? Photos?

Get the info about the IC's near the burned resistor. There are 2 Zeners nearby and several transistors and M11. Draw out the circuit with R83 in it and see what it's attached to.

T

[Francisco.s]

Re: IMAC 24 PSU Bad Caps replacement

There seems to be a protection diode conected to pin 9 (mosfet output driver) of the NCP1381, and it was bad. (leakage)
Now, it has drain pulses. One burst of pulses, and then it autoprotect.
I dont know if it is due to r83 in bad condition. (altered value) This resistor goes to pin 3 (DMG) of the same NCP1381 through another resistor, that is in good condition.
Step by step to the solution.

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

Where is the NCP1381?

I attached the datasheet.

T