Does humidity effect bad cap symptoms?

[T^2]

I have a Dell 8400 purchased new in October of 2004. Recently it started to shut down sometimes during POST and sometimes while the OS is loading. Usually cycling the power a few times brings it up and fully functioning. Once there it will work fine for as long as I like. Yesterday we had an unusually humid storm come through here and I could not get the machine to come up at all. Today we are much drier and the machine took it's normal 3 times power cycling and came up. Has any one else noticed a humidity and/or temperature factor in the bad cap symptoms or a bad power supply?

Opened the box up and all caps look fine except for one 2200 ufd Nichicon by one of the memory sticks. A mound of brown stuff on top. See my out of focus pic. I am going to replace it but should I replace more of them? None of the others show any sign of leakage or the slightest bulging.

Also noticed all the caps have what looks like a mark on the top made with a blue marker. Is that a Dell production step to mark the caps have been double checked?

[Gianni]

Re: Does humidity effect bad cap symptoms?

Welcome on Badcaps.

About Nichicon they are good caps but in the past (2001-2004 IIRC) they had some problems with some types (HN or HM IIRC).
So I think you have one of them on your board.

If you can list caps/brands it will be useful to have good advice from members.
Some caps don't show sign when they go bad but knowing brand and series you can have an idea about them.
Usually if one caps is dead also the others have problems.

Try to post better pictures.

For PSU you can open it a see if something is wrong with caps.

About blue mark I don't know.
Humidity/temperature? I had never problem with them except with an old Athlon 700MHz that crashed continuously when the ambient temperature was over 35ºC (summer 2003).

Ciao
Gianni

[T^2]

Re: Does humidity effect bad cap symptoms?

Gianni

Thanks for the reply. There is HN(M) on the cap as well as H0428. Lots of Nichicon caps but also Rubycons. Managed to get a better pic of the cap.

[shadow]

Re: Does humidity effect bad cap symptoms?

The HN(M) caps have failed. The ones that you have must have been affected by the manufacturing defect that Nichicon had between 2001 and 2004.

[T^2]

Re: Does humidity effect bad cap symptoms?

I have some more info on this failure. Since it's intermittent I thought I would try an old but effective tool - the hair dryer. I first tried heating up the area of that bad cap in the picture - no change. I next tried the area of the expansion cards - no improvement. I eventually found out if I blow hot air into the power supply for about 3 minutes and then turn it on the machine comes up. So whatever is wrong likely has to do with the power supply. I need to find one I can swap in temporarily to confirm my theory.

[370forlife]

Re: Does humidity effect bad cap symptoms?

Regardless you still need to fix those caps.

[PCBONEZ]

Re: Does humidity effect bad cap symptoms?

H0428 indicates week 28 of 2004.
That was during the run of defective Nichicon HN and HM series'.
You should replace all HN and HM caps on the motherboard.

You may have issues with the PSU too but those bad mobo caps need to go either way.

.

[T^2]

Re: Does humidity effect bad cap symptoms?

Just an update from the bad cap computer no less.

It looks like I fixed it - God willing. Remember I said a hair drier to the power supply would bring the computer up on cold days. Well it occurred to me that with electronics when symptoms change because of temperature it is usually a mechanical connection problem. So I took the power supply out and disassembled it so I can see the solder side of the main pcb. Well I noticed that a small daughter board had some heat discoloration near the edge. I got the old eye loop out and inspected the area. Sure enough there was a small transistor that the solder on all three leads looked like cold solder joints. Two of them were cracked all around the leads - not good connections! I removed the old solder and re-soldered new. I also removed some RTV around the transistor body and stood it straight up so air would flow all around it. I reassembled the PSU, put the computer back together. Crossing fingers I turned it on and it came up the very first time and has been running for a few hours now with no problems.

I probably should still replace the bad cap and a few more on the motherboard when I get a chance but it's nice to have this machine come up when I want it to not when it feels like it.

[PCBONEZ]

Re: Does humidity effect bad cap symptoms?

NICE.
Good thinkin' too!