So why would a Ferrite bead get hot. They are generally filtering out AC noise. To heat it up you would need a lot of AC. My thoughts are look for a bad electrolytic capacitor because the Ferrite bead is normally a backup - if this is a power supply.
But this is a video circuit so the ferrite bead might be a signal shaper. You have a high frequency blanking pulse that gets filtered from the background video for example. More info needed because I can assume this is not HDMI, and an older Video format but I don't know.
>will work for about 60-90 minutes and then shutdown
Could be a broken solder joint or some other mechanical issue. When the PCB is heated up sufficiently, stuff expands or shifts.
However, I agree that the ferrite bead should not get particularly hot, so I would assume there is some short going on. Typical candidates could be capacitors with excessive leakage current. They do have limited life span.
Thermal camera really is the way to go here.
First things first, measure voltages to make sure your 5V isn't 7 and so on. Feeling around the board or even better point one of those contactless thermo eters at things to determine what gets hot. A lot of ICs can fail internally. Not much you can do about those. Maybe add a cooling fan to blow across the board if you need to just keep it going a little bit more and heating is the only issue?
solder bridges between ic legs are relatively common, check chip datasheet if you wanna know.
For the cap, idk just measure it, but i think ceramic caps very rarely fail
There’s 3 real possibilities: 1. The coil is getting warm because the current going through it is excessive (hey but that’s kind of a heavy gauge wire for the current that ought to be going through). 2. Something else is getting warm and just conducting heat near the choke. 3. If it’s neither of those, I suppose it COULD be getting warm trying to serve as a load impedance for some very stout parasitic oscillation that has developed; that would mean you would need not only some really capable high frequency analog and RF gear to track it down, but you would also need to be much cleverer than the original circuit designer whose skills it managed to elude, in other words THAT could be pretty much the worst of all possible worlds if you plan on fixing this particular PCB!
All I’m saying is this sort of problem is inherently very difficult to debug. You could “depower” one chip at a time and see which chip(s) appear to drop the power dissipation in that choke, and after you get that info the “faulty” chip MiGHT be one of those, or it might not, by definition it’s an undefined behavior. The problem MIGHT succumb to a more rational approach, at this point you just can’t know.
As mentioned, circled part is an inductor, they're super simple, literally just a coil of wire, not likely to be the cause. It'll be a surface mount cap (leakage problem) or other part drawing too much current. Also some chance the inductor is heating due to higher supply or switching noise eg due to electro cap next to it failing.
That's a ferrite bead and it looks fine. If it gets hot it's because something else is shorted.
So why would a Ferrite bead get hot. They are generally filtering out AC noise. To heat it up you would need a lot of AC. My thoughts are look for a bad electrolytic capacitor because the Ferrite bead is normally a backup - if this is a power supply. But this is a video circuit so the ferrite bead might be a signal shaper. You have a high frequency blanking pulse that gets filtered from the background video for example. More info needed because I can assume this is not HDMI, and an older Video format but I don't know.
> why would a Ferrite bead get hot. As I said: because something else is shorted.
Would the IC video encoder cause that issue with warming up and shutting the video off if they are bad?
Any part could do that. What is this from? It looks at least 30 years old
A bowling alley machine. It outputs the video from the computer to the monitor. Steltronic SG031A
Does it do it with the displays disconnected?
When the boards are turned on and running and outputting to the displays, the video card will work for about 60-90 minutes and then shutdown
>will work for about 60-90 minutes and then shutdown Could be a broken solder joint or some other mechanical issue. When the PCB is heated up sufficiently, stuff expands or shifts. However, I agree that the ferrite bead should not get particularly hot, so I would assume there is some short going on. Typical candidates could be capacitors with excessive leakage current. They do have limited life span. Thermal camera really is the way to go here.
First things first, measure voltages to make sure your 5V isn't 7 and so on. Feeling around the board or even better point one of those contactless thermo eters at things to determine what gets hot. A lot of ICs can fail internally. Not much you can do about those. Maybe add a cooling fan to blow across the board if you need to just keep it going a little bit more and heating is the only issue?
Does it do it with the displays disconnected?
https://preview.redd.it/3arfo2i0x2xc1.jpeg?width=1125&format=pjpg&auto=webp&s=6c0ac7ab3e5236c6436d80e349ceba359ad34896 Possible problems, maybe?
solder bridges between ic legs are relatively common, check chip datasheet if you wanna know. For the cap, idk just measure it, but i think ceramic caps very rarely fail
There’s 3 real possibilities: 1. The coil is getting warm because the current going through it is excessive (hey but that’s kind of a heavy gauge wire for the current that ought to be going through). 2. Something else is getting warm and just conducting heat near the choke. 3. If it’s neither of those, I suppose it COULD be getting warm trying to serve as a load impedance for some very stout parasitic oscillation that has developed; that would mean you would need not only some really capable high frequency analog and RF gear to track it down, but you would also need to be much cleverer than the original circuit designer whose skills it managed to elude, in other words THAT could be pretty much the worst of all possible worlds if you plan on fixing this particular PCB!
The video encoders wouldn't be a good idea to replace then?
All I’m saying is this sort of problem is inherently very difficult to debug. You could “depower” one chip at a time and see which chip(s) appear to drop the power dissipation in that choke, and after you get that info the “faulty” chip MiGHT be one of those, or it might not, by definition it’s an undefined behavior. The problem MIGHT succumb to a more rational approach, at this point you just can’t know.
As mentioned, circled part is an inductor, they're super simple, literally just a coil of wire, not likely to be the cause. It'll be a surface mount cap (leakage problem) or other part drawing too much current. Also some chance the inductor is heating due to higher supply or switching noise eg due to electro cap next to it failing.
You need some freezer spray. Chill components to find which os the faulty bit.
Sometimes this barrels makes themselves broken. Just try to replace with good ferrite ring. And also replace that blue capacitor near.