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Electrical engineering questions
I rescued an HDTV a few days ago and have been trying to repair it. While it turns on, it goes to standby after between thirty seconds and three minutes.
Turning it back on again causes it to do the same thing but in only a few seconds, which lead me to think the problem is heat related.
The heatsink on it's processor seemed to have partially peeled off (It looked like a piece of metal tape folded over.) so I replaced it with some GPU RAM heatsinks but this didn't fix things.
I'm now looking at the PSU which is buzzing slightly, trying to find the culprit (I'm trying putting my ear against a very dry bottle and pressing the end against components in the hope that the buzzing component will transmit sound through the bottle.).
My current reasoning is the PSU is cutting out, but, as the power switch circuit is still engaged, it comes straight back to standby.
Any ideas which component causes this kind of fault? The buzzing seems to be coming from the top right of the PSU board. I'd have suspected the capacitor, but that seems to be glued to the board, so it wouldn't vibrate.
Turning it back on again causes it to do the same thing but in only a few seconds, which lead me to think the problem is heat related.
The heatsink on it's processor seemed to have partially peeled off (It looked like a piece of metal tape folded over.) so I replaced it with some GPU RAM heatsinks but this didn't fix things.
I'm now looking at the PSU which is buzzing slightly, trying to find the culprit (I'm trying putting my ear against a very dry bottle and pressing the end against components in the hope that the buzzing component will transmit sound through the bottle.).
My current reasoning is the PSU is cutting out, but, as the power switch circuit is still engaged, it comes straight back to standby.
Any ideas which component causes this kind of fault? The buzzing seems to be coming from the top right of the PSU board. I'd have suspected the capacitor, but that seems to be glued to the board, so it wouldn't vibrate.
Comments
Seriously though, we had a dodgy DVR that was having heat problems and after long and arduous googeling I finally managed to track the problem down to a ¢15 thingamajig on the circuit board that should have been a ¢50 thingamajig unless you want the DVR to fail after a year or so. The guy who tracked the issue down was an electrical engineer who designed similar DVR circuit boards.
Hopefully this guy will have the whole PSU board, which will mean just unplugging and screwing without need for soldering.
I'm stumped for now. I'll work it out in time.
One paper listening trumpet later and it's definitely the top right transformer making the buzzing noise.
Transformers especially tend to buzz, as can capacitors and thats not particularly unusual.
If you have some components getting particularly warm look up the serial number on it for it's operating temp. Chips and transformers can get reasonably hot, capacitors generally shouldn't unless they're high voltage even then they shouldn't be more than warm to the touch.
Beyond that check for solder breaks or melts. A decent multimeter should be able to do a continuity test. On a break often just reheating it will fix the problem.
Going to have to look into where to buy capacitors.
When I say I rescued the TV, I literally found it face down in someone's garden. They'd thrown it out when they moved.
The titles are chopped off, It's placement --> Capacity in uF and Voltage in V.
My problem is C853 (160V 1uF); I've bought all the others but I can't find a radial capacitor that fits it's specs without ordering from the US. Can I use a ceramic capacitor or do they behave differently?
Also, what's good for removing rust from circuit boards?
I have a replacement light switch to install. The current one looks like a standard wall switch dealie.. it's in a little metal box, etc. I can post pictures if anyone wants them.
The one I want to install is a "deep socket" switch. Basically a rocker switch with some stuff over it.
What should I know going into this? Since my arm is currently all tingly I realized quickly that I will need to turn the power off prior.
EDIT: more detail, less snark. I do appreciate the help.
Essentially three sets of headphones in one housing. The rear left speaker is no longer responding, I took them apart and it seems the problem is a break in the wire somewhere according to the multimeter.
I'm suspecting the jack is the culprit, what are other people's experiences with headphones breaking?
It's the middle one. Do people still think it's the most likely break point? Problem is the three cables fuse into one shortly there after so once cut, there's not a huge amount to work with.
One problem I find with them is that any sudden loud sounds or really bassy noises cause the volume to drop for a short time and then fade back up.
This has only become a regular problem with the shotgun in BF3 which sounds like a beast but drops the volume for a split second each time it's fired.
So, would putting a capacitor in-line with the batteries allow for the sudden power drain without causing the volume to drop out?
I'm going to go remind myself how amps relate to farads.
The bad news: AAA batteries can have varying discharge rates.
Good news: There is probably a capacitor already in there I can swap out for one with a greater capacity.
The batteries seem wired in series so a 2.4v current but I can't work out the power draw as the drain isn't constant. I've seen it at 100mA idle.
For future reference:
Another thought I've had is using this video with full and mostly empty batteries to see if it's taking it's time to come back depending on available charge.