K7000 19" cap question

tester007

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I got a nice 7000 monitor. It worked great on install, but when I went to adjust the horizontal position it started to crackle and go in and out of shutdown with the screen looking like it would collapse to a vertical line in the center. Eventually it wouldn't come back on. I took out the chassis and re-soldered a ton of areas. The caps on it look like they were redone, and I took a few off and checked and all were good. I still replaced those I took off though. The board was ak, but it may have been coincidence, but when I wiggled the aluminum heatsink on the right side (when looking from the back) it started doing it again. So I reflowed all that area. Now the monitor seems to be ok. I have run it for a long time without the problem. But when checking around afterwards wiggling stuff to see if it was a short somewhere causing the issue, I noticed that the 47uf cap at c37 (I think thats the location) is warm to the touch on the top.
I don't poke around monitors much once they are running, so I don't know is this is normal or not? All others seem cold or room temp to the touch.
 
well, you shouldn't be poking around monitors when they are running - especially with your fingers. Get a plastic tool for that.

It's not uncommon for big parts to be warm when current is flowing through them. That's why they're big, to handle the load and dissipate heat. If you got the issues fixed with your solder repairs, and it's working good now, I'd leave well enough alone and quit messing with it unless you have further issues...
 
I'm not confident the issue is solved. It wasn't there until I went to adjust the horizontal, then went away after the first reflow, then came back. If this was to be my machine I could have a wait and see attitude but its not so I want a certain level of confidence in it... which involves checking for bad connections via wiggling things or putting pressure in areas to see if its a trace. I have a plastic tool as well, and caps don't have a charged casing, or know of any charged heatsink in any application.

Resistor size as far as heat dissipation makes sense as the casing size can be adjusted without affecting its core value. A capacitors size on the other hand is more a result of the manufacturing to meet a certain capacitance, and to a lesser effect, voltage rating. Larger the capacitance the more wraps, therefore the larger it is. I don't think there is any thought to heat dissipation as I have never seen any spec on that.

But back to the original question, I know some things get warm, but specifically asking about electrolytic caps. I have never seen it before, but maybe I just never noticed. If a typical cap was put in that place a factory 85 degree spec, then I would think it shouldn't be warm. Room temp is 22c so if I touch it and its warm, its generating heat higher than that itself let alone any ambient raising it more while in use. I'll put the fluke temp probe on it today and get an acurate temp. From what I know, heat should only be generated when exceeding ripple tolerance. So for this specific cap, either something is wrong (maybe?) Or its normal in that spot. Its not exactly high precision stuff we are working on which is why I am considering it 'could' be normal..

Thanks
 
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i would still look for some cracked traces around the vertical IC to make sure they are ok. that heat sink gets handled allot when taking it in or out of the frame.

as far as the cap getting hot i would run it for a fuw hours and see what it does. if it is stable then leave it be.

Peace
Buffett
 
Its run for 2 days now with no issue... I just like to be sure if its going to someone else. All caps measured in the low 20's all the time it ran. That 47uf one was around 45 degrees or so all the time so well within its range. But every 10 degrees halfs the life. I measured the big 560 cap in circuit and it was about 20% off so this could be the reason for the 47 warming up. I don't really want to change anything else if I can avoid it since the picture is awesome on this. So I think I will just leave it be.

Thanks
 
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