Main > Monitor/Video Forum
FIXED - CRT Top of the screen folding over?
Zebidee:
I'm having trouble aligning all the parts I see on the photos with your schematic. For example, I can't see where those transistors are. Maybe I'm tired, or going blind, or maybe it is not exactly the right one for your TV.
In any case, the prefix "L" indicates that it is an inductor. Blue suggests "high-voltage"? To identify, there should be a three-color coding, 2 dots on top and a stripe.
For example, as described here: https://coil32.net/design/color-marking.html
These inductors would be of simple coiled wire construction inside. It is uncommon for inductors like this to fail, but when they do they can create a lot of heat.
You can test inductor vs capacitor, without removing from PCB, by using multimeter in ohms mode. Inductor should show low resistance, a few ohms, capacitor should show high/infinite resistance (OL). I also use a "Multi-function Tester T7", which can be purchased cheaply from your favourite online retailers. You'll need to remove it from the PCB for this. Here is a video:
Having a second look at your photos, I also see the blackening/carbonisation occuring on the underside of the PCB at the same spot.
LTC:
--- Quote from: Zebidee on July 02, 2025, 12:30:20 pm ---I'm having trouble aligning all the parts I see on the photos with your schematic. For example, I can't see where those transistors are. Maybe I'm tired, or going blind, or maybe it is not exactly the right one for your TV.
In any case, the prefix "L" indicates that it is an inductor. Blue suggests "high-voltage"? To identify, there should be a three-color coding, 2 dots on top and a stripe.
For example, as described here: https://coil32.net/design/color-marking.html
These inductors would be of simple coiled wire construction inside. It is uncommon for inductors like this to fail, but when they do they can create a lot of heat.
You can test inductor vs capacitor, without removing from PCB, by using multimeter in ohms mode. Inductor should show low resistance, a few ohms, capacitor should show high/infinite resistance (OL). I also use a "Multi-function Tester T7", which can be purchased cheaply from your favourite online retailers. You'll need to remove it from the PCB for this. Here is a video:
Having a second look at your photos, I also see the blackening/carbonisation occuring on the underside of the PCB at the same spot.
--- End quote ---
I don't think the schematic is correct for the chassis. Here's a closer look at the area in question
Zebidee:
--- Quote from: LTC on July 02, 2025, 01:17:57 pm ---I don't think the schematic is correct for the chassis. Here's a closer look at the area in question
--- End quote ---
Reckon so too, and thanks for the new pic.
Don't want you to break anything, but maybe you could pull it off to get a closer look? There could be markings on side/below we cannot see from above. You could also possibly measure it using one of those meters.
You can confirm if it is an inductor by just using your DMM in ohms mode, as described above.
If it is an inductor, the red dot suggests "2" but without more markers or clues we wouldn't know if it is 22mH or 2200mH, for example.
OTOH, on your latest photo I see there is a dot on the PCB that aligns with the red dot, so possibly just a polarity marker?
You might want to check how hot it gets when TV is powered on. In the ideal world you'd have a thermal camera or a thermal probe for a multimeter, but realistically you probably don't. Failing that, and if you are feeling brave, maybe you could carefully hold a finger nearby.
LTC:
--- Quote from: Zebidee on July 03, 2025, 12:05:09 am ---
--- Quote from: LTC on July 02, 2025, 01:17:57 pm ---I don't think the schematic is correct for the chassis. Here's a closer look at the area in question
--- End quote ---
Reckon so too, and thanks for the new pic.
Don't want you to break anything, but maybe you could pull it off to get a closer look? There could be markings on side/below we cannot see from above. You could also possibly measure it using one of those meters.
You can confirm if it is an inductor by just using your DMM in ohms mode, as described above.
If it is an inductor, the red dot suggests "2" but without more markers or clues we wouldn't know if it is 22mH or 2200mH, for example.
OTOH, on your latest photo I see there is a dot on the PCB that aligns with the red dot, so possibly just a polarity marker?
You might want to check how hot it gets when TV is powered on. In the ideal world you'd have a thermal camera or a thermal probe for a multimeter, but realistically you probably don't. Failing that, and if you are feeling brave, maybe you could carefully hold a finger nearby.
--- End quote ---
I do actually have a thermal probe for my multimeter. I'll dig into this issue again sometime this week.
LTC:
I am getting an open circuit when measuring across the blue component.
My temperature probe is unfortunately not working. The readout stays on 80*F no matter where I place the probe. I will need to get a replacement.