Re: bad cap? (slightly high ESR reading, slightly low capacitance reading)
thank you for the info.
I guess the part I did not understand is how when you look at the "in circuit ESR values", we can clearley see that cap 11 is unusually high compared to the others, followed by cap 13. But if you look at the ESR value for out of circuit (where the reading SHOULD be more accurate) they all show the same reading of 0.10. So in other words it seems the reading is more accurate when the chips are in circuit. Or could that be a coincidence maybe?
kq702
Member
Last Activity: 11-25-2012, 06:31 AM
Joined: 07-03-2012
Location: auburn ma
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bad cap? (slightly high ESR reading, slightly low capacitance reading)
Hi I had a circuit board that had a problem with the monitor not turning on. Sometimes it would turn on, other times it would stay black and would not be detected by the computer. The problem got worse and worse, eventually the monitor did not turn on at all when connected.
I recently purchased an ESR meter and was testing the caps on this board, and I came across two posable caps that may be bad, (though no physical damage shows).
Below is a chart I made with all the info I gathered. Note all caps are rated at 6.3 volts, 1000 uV.
[ATTACH]51613[/ATTACH]... -
Re: did I kill the board? too much heat decapping :-(
Thank you for the info. I was going to try to make sure no leads were shorting before I powered it up, so I removed the cap and cleaned the board and after I did that it does not look as bad, but clearley damage is done to 4 wires. Still have not powered it up but I think I am going to attempt to repair the damaged leads. I never did any repairs like that before but I think I will give it a try. Gonna start researching how to do that next! I know its difucult but its worth a try.
[ATTACH]51422[/ATTACH]
...Leave a comment:
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Re: did I kill the board? too much heat decapping :-(
Oh yeah one more question- is that a bad method that I used does anyone think? (trying to heat the pins by adding hot solder to the bottom of the board right over the pad).
Something else I did several times is get a big glob of solder and hit both of the cap leads, and put the solder iron in the middle. The liquid solder will heat legs of the capacitor and eventually it will slide right out.
Is that a bad method? I it seemed to work for me for a while (untill I ran into this one today).Leave a comment:
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Re: did I kill the board? too much heat decapping :-(
Hi again! I only saw a partial pad left on one of the holes :-( But they may just be covered in the black smog I am not sure.
After taking a closer look I noticed multiple wires torn in that area as well :-(
For anyone intrested in seeing better photos- them photos I uploaded in my original post came out so bad and I got so sick of my camera that I decided to go buy a better one tonight so the first test shots were of this board. This camera is much better!
[url]http://img.photobucket.com/albums/v229/mds33200/DSCN0005b.jpg[/url]...Leave a comment:
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Re: did I kill the board? too much heat decapping :-(
Darn, not a good sign when a badcaps veteran says its gone. I have done several boards before and I did not have trouble like I did with this board- it seemed the normal temp I usually use didnt even melt the solder. I tried a new method (putting solder on the desolder iron, and letting the liquid solder do the melting arround the cap legs). It seemed to work on most of the chips, but this one I had it on a little bit too long cus it would not budge.
Is it better to use hot air? or any other sugestions?Leave a comment:
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did I kill the board? too much heat decapping :-(
I can see an area where atleast one wire is ripped (and the connection is broken). I noted that wire with the red arrow in the pic below. Should I even try to reinstall the board to see if it works, or did I kill it?
[ATTACH]51093[/ATTACH]
Here is another angle. the red dots are the terminals of the capacitor that I reinstalled.
[ATTACH]51094[/ATTACH]I can see an area where atleast one wire is ripped (and the connection is broken). I noted that wire with the red arrow in the pic below. Should I even try to reinstall the board to see if it works, or...Last edited by kq702; 11-17-2012, 04:51 PM. -
question about installing a cap rated for a lower temp
Hi I have a motherboard which is untested however I can see it has one visibly bad cap. It is 6.3 V, 3300 uF, and the temp is rated at 105 C.
I have a spare cap laying arround that is the exact same physical size, and has mostly the same specs. The only difference is the spare one is only rated at a temp of 85 C, not 105.
I understand that installing this one is not a good long term solution, however if I install it will it work for even a small amount of time? I just want to test the motherboard. If I install it and the motherboard works I will remove it and order... -
question about solder paste (cell phone board)
Hi I have several very small components on some cell phone boards that have to be replaced (surface mount) and I think the best way to apply the part it is to use small drops of liquid solder paste and place the component down then heat it up with hot air nozzle but I am not sure what the best type of solder paste to use? Lead or lead free solder paste?
The stuff I got is no clean lead free OM-338 but I have to ordre more since my stuff is expired, but I was checking if lead solder paste would be better for my application? -
Re: question about reflow- it it ever a long term solution?
I couldn't find the Kester 951 no clean flux here locally so I ordered it from ebay. I got a needle dispenser bottle to dispense it too- its much cleaner then using a dropper. I just feel like it evaporates way too fast though, but I am new to this. I feel like by time the temp gets up all the flux has evaporated off. Is this normal?...Leave a comment:
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Re: question about reflow- it it ever a long term solution?
Thanks for everyone for the feedback and suggestions. What type of flux do you suggest using? I have some Kester 951 no clean flux, would that type be good? Or would a more tacky flux be suggested?Leave a comment:
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question about reflow- it it ever a long term solution?
Hi I did a reflow on an HP laptop a while back- it was a DV6000 series. The original problem was the internet stopped working- turns out the south bridge chipset was causing the issue (its a very common issue I found out after searching online). Some people said they did a reflow on the south bridge chipset and that fixed it, but lots of people warned that it will not last. They said the only true solution was to reball with lead solder. So I gave the reflow a try- it worked but they were right it only lasted about a month.
So I recently had a customer bring me a mac book...
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