I have a Panasonic 27" CRT from 2001 (Model CT27D11E) and I took the boards out to clean them. I noticed that 3 different parts of the main board were a much darker brown than the rest of the board. More specifically, this was in the power supply section and vertical and horizontal deflection areas. I'm assuming this is from when the board would heat up during use and eventually it got hot enough that it darkened the PCB in those areas. I will note that in the areas where the PCB is darkest, that is were the components are really crowded and packed into a very small space.

When a CRT PCB gets darkened areas like this, does it mean that the TV was used a lot? How many hours of operation would it take for a PCB to get darkened areas like this? The tube in this set is still bright and sharp and the colors still look vibrant.

I've encountered sets that were fairly clean inside (but not so clean that they had clearly been washed up) with burned up resistors, etc.

Some TVs just had kind of bad power supply designs.

However, if you're seeing dark spots in the deflection area, that kind of sounds like high hours.

In general, the amount of soot on the flyback and the bell housing of the CRT is a much better indicator of use because the high voltage attracts the soot.

If it's got a lot of soot, and it has dark spots on the boards near big power resistors and the deflection, you are looking at a high hour set.

"Soot" is different that "dust" in that it's very fine and usually black. The high voltage attracts tiny particles in the air and they stick directly to the internal surfaces. The "dust" will just be solid dirt and bunnies inside the thing.

Likewise, if there's a lot of soot and no burn marks, it's also probably high hour. Not all sets had power supplies that burned up the PCBs. Personally, I see that a lot more in sets from the 80s where the part count is started to get reduced, but they don't have the simplified and optimized designs that started to appear in the mid 90s.

I've encountered sets that were fairly clean inside (but not so clean that they had clearly been washed up) with burned up resistors, etc.

Some TVs just had kind of bad power supply designs.

However, if you're seeing dark spots in the deflection area, that kind of sounds like high hours.

In general, the amount of soot on the flyback and the bell housing of the CRT is a much better indicator of use because the high voltage attracts the soot.

If it's got a lot of soot, and it has dark spots on the boards near big power resistors and the deflection, you are looking at a high hour set.

"Soot" is different that "dust" in that it's very fine and usually black. The high voltage attracts tiny particles in the air and they stick directly to the internal surfaces. The "dust" will just be solid dirt and bunnies inside the thing.

Likewise, if there's a lot of soot and no burn marks, it's also probably high hour. Not all sets had power supplies that burned up the PCBs. Personally, I see that a lot more in sets from the 80s where the part count is started to get reduced, but they don't have the simplified and optimized designs that started to appear in the mid 90s.

How many hours would you consider high hours? Chances are that my Panasonic set is a higher hour set. There was some soot on the tube and on the flyback but not a huge amount. I will say that the picture still looks very good. I always thought it was a low hour set until I took the back up. One other thing is that this TV has 1 composite input on the front and on the top of the PCB where this composite input is, the PCB is black around some of the components. It's not charred by there is a black color. The bottom of the board is not black at all. I'm wondering if the set is still safe to operate if there is a little bit of black on the PCB?

How many hours would you consider high hours? Chances are that my Panasonic set is a higher hour set. There was some soot on the tube and on the flyback but not a huge amount. I will say that the picture still looks very good. I always thought it was a low hour set until I took the back up. One other thing is that this TV has 1 composite input on the front and on the top of the PCB where this composite input is, the PCB is black around some of the components. It's not charred by there is a black color. The bottom of the board is not black at all. I'm wondering if the set is still safe to operate if there is a little bit of black on the PCB?

I never really though about it tbh, but if you consider that a high hour set could have been used for 10 years, for 3 hours a day, maybe 5 days a week or more, that's 7000-10,000 hours.

One of the older members here that did professional repair work would have a better answer.

Yes, it can be bad or dangerous in some cases to run a TV that has obvious black charring on the PCB. The black stuff is carbon, and carbon is conductive. If there's enough electrical potential on the carbon burn mark, it can cause arcing. I've never had it happen to me, but I've seen videos on YT that showed it happening.

Generally though, mild darkening or discoloration isn't a problem, just actual carbon burn marks or charring. There's stuff you can do to cover it up. When I find areas like that, I typically replace the resistors with something beefier with longer legs and solder them off the PCB a good ways to allow the heat to dissipate better. Not sure if that's the best thing to do, but it makes me feel better.

There were some people who used their sets 8+ hours a day every day until it wasn't repairable or they upgraded. Some places were even worse. There's a thrift store here that used to be a large supermarket (there's one or two other businesses that have similar) and at the entrance leftover from the supermarket days is a 90s-00s era Sony consumer TV hooked to a camera that captures everyone walking in so you can see them filming you...That thing still works, and I don't think they ever turn it off...It must have an impressive hours count.