MS-7548 Replaced Caps - No Fix

[ferbfletcher]

I replaced caps on a MS-7548, as indicated in the other MS-7548 thread. https://www.badcaps.net/forum/showthread.php?t=14659

However, after replacing all of the TK caps, it still won't post.

After pressing the power button, the CPU fan spins for about 1 second and then it stops. No post, no beeps, no video. The power supply turns on and the hard drive spins up. I also tried another known-working power supply.

This was the same symptom before replacing caps.

Are there any components that could have gotten damaged by the bad TK caps?

For pictures, see https://www.badcaps.net/forum/showthread.php?t=14659 my board and caps look exactly like that.

I replaced all the ones around the CPU, then there were some on the other sides that got replaced as well. They were all 6.3v 1800uf brown TK caps.

Any ideas?

[mockingbird]

Re: MS-7548 Replaced Caps - No Fix

1) What did you use to replace them?
2) Did you address all the other off-brand caps on the motherboard, and not just the VRM caps?
3) Seeing as how this motherboard comes off an HP Tower, I'm assuming that you have a Bestec PSU in there... Given the age of this machine, you should really have a look inside the power supply, or consider getting a brand new power supply completely.

If you don't want to fiddle with the power supply, Newegg has the Seasonic S12-II 380 for $50 shipped: http://www.newegg.com/Product/Produc...82E16817151072

[ferbfletcher]

Re: MS-7548 Replaced Caps - No Fix

I replaced all of the TK 6.3 1800uf caps, as they were all buldging and leaking badly. I replaced them all with Panasonic FL 6.3v 1800uf.

i replaced 9 around the CPU, and 6 elsewhere on the board.

All the other caps appear to be okay, and they are not TK (except for some very tiny one's that might be, but they are not buldging or leaking.) Those would be quite difficult to replace, as they are very small.

About the power supply... I have another known-working power supply that I am also trying on it, so the power supply is not the issue.

The board is getting power, because the CPU and other chipsets warm up, but the CPU fan stops after 1 second, and there is no post, no video. Monitor stays asleep.

The power light comes on, and I can power off the power supply by holding the computer power button in for a few seconds.

[mockingbird]

Re: MS-7548 Replaced Caps - No Fix

Does the fan twitch, or does the fan spin and then stop after one second? Where did you get your Panasonic FL from (Important to know, since you may have bought fakes)?

[c_hegge]

Re: MS-7548 Replaced Caps - No Fix

I think he is saying that the CPU fan stops after a second, but the PSU and other parts like the drives keep running. I doubt if it's a shorted FET.

[ferbfletcher]

Re: MS-7548 Replaced Caps - No Fix

Does the fan twitch, or does the fan spin and then stop after one second? Where did you get your Panasonic FL from (Important to know, since you may have bought fakes)?

When I plug in the power cable, the fan spins for just a tiny instant, as it does on many computers.

When I push the power button, it spins for a bit longer, like a full second, then it stops spinning (as though it started to run, but then something causes it to power off).

If I power it without RAM, it does the exact same thing. I've tried other ram sticks in other slots to eliminate the chance of bad RAM.

Where did I get the Panasonic FL from? I don't remember. They are some I had, they came from some electronics store.

They are black with gold printing.

Some of them have a "squished" [M] logo, like it is much shorter than it should be. The same width, but not as tall (the logoo). They aren't all that way, but some are. Does that definately mean fake? Or do real ones sometimes vary in printing like that? They are all in the same cardboard roll, so they all came together.

They all have a strip of red lettering down the side, it says 47VVK


Anyway, is there somewhere on this motherboard that I should check for certain voltages?

[mockingbird]

Re: MS-7548 Replaced Caps - No Fix

Whichc electronics store would stock Panasonic FL? Most likely they are fake, but post a picture.

[ferbfletcher]

Re: MS-7548 Replaced Caps - No Fix

Here are the pictures.

[mockingbird]

Re: MS-7548 Replaced Caps - No Fix

In my opinion, they're the real thing. The next thing which comes to question is the quality of your work. Did you do a good job? Did the solder take? Also, check the other caps on the board... I notice a variety of caps scattered throughout, but what I'm particularly interested in are those Toshin Kyogo caps near the memory slots.

[ferbfletcher]

Re: MS-7548 Replaced Caps - No Fix

In my opinion, they're the real thing. The next thing which comes to question is the quality of your work. Did you do a good job? Did the solder take? Also, check the other caps on the board... I notice a variety of caps scattered throughout, but what I'm particularly interested in are those Toshin Kyogo caps near the memory slots.

There are 4 TK by the memory slots, they are the same as the others, 6.3v 1800uf. I replaced those along with the ones next to the CPU.

Also, there are 2 TK to the left of the CPU, and 1 TK to the right of the CPU. Those are also the same, 1800uf 6.3v and I also replaced those at the same time.

About the quality of the job. I looked over them all again, and the solder appears to have taken on all of them.

I measured the voltage at each cap.

At all the ones around the CPU, it was 1.1v

The voltage on those around the ram was 1.8v

The remaining was 5 volts.

[mockingbird]

Re: MS-7548 Replaced Caps - No Fix

Good, you did indeed get them all.

1.1v on VRM in or out... Anyone else care to pitch in on this? That doesn't sound right. RAM voltage sounds OK.

[Player2]

Re: MS-7548 Replaced Caps - No Fix

Did you ever get anywhere with this board ferb? I'm having the exact same issue- recapped and it still spins the CPU fan for about a second then stops, no POST, no beeps, etc. Will not spin up again until I unplug/replug the PSU.

I'm using a known good PSU, CPU, and RAM (all working on another AM2 board.) Replaced the VRM caps with polys, others with Nichicon HZ and HN, everything 6mm and larger were replaced. I also had some FETs that were shorted or reading off, both in and out of circuit. Replaced those, still no change. Any ideas on other things to check? Components that often fail along with FETs?

Thanks!

[momaka]

Re: MS-7548 Replaced Caps - No Fix

I'm having the exact same issue- recapped and it still spins the CPU fan for about a second then stops, no POST, no beeps, etc. Will not spin up again until I unplug/replug the PSU.

Going by that description, there must still be a short circuit somewhere on the board. Check your MOSFETs again. If none appear to be shorted, then the best troubleshooting method would be to start disabling voltage rails on the motherboard one by one (by removing certain MOSFETs or certain pairs of MOSFETs) until the board starts. Shorted ceramic caps can also be responsible for this.

[Player2]

Re: MS-7548 Replaced Caps - No Fix

Well I got it running... Turns out that the CPU fan I was using was not turning enough RPMs (it's an oversized fan/cooler) and the mobo was kicking off immediately- no beeps, no error messages, etc. Once I plugged another fan into the CPU fan header and plugged the CPU fan into the system fan header, it came up and immediately gave me a message that the system fan was failing. Anywho, it's running great now. Guess I missed this because the other board I was using to verify the components had no problem with the CPU fan running 800-1000 RPM.

Thanks for the help Momoka, glad it turned out to not be a huge problem! And Ferb, if you're still around, try plugging a different fan into the CPU fan header.

[momaka]

Re: MS-7548 Replaced Caps - No Fix

Thanks for the help Momoka, glad it turned out to not be a huge problem! And Ferb, if you're still around, try plugging a different fan into the CPU fan header.

Well, nothing to thank me for. This is definitely a case where I am glad that you actually didn't follow my advice . Congrats on the fix too!