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Television Service Question

Outland

Outland

Active Member
Hello all,

I'm not really sure if this is the right place, so if it's not, please move it or let me know.

My CRT television, bought during 1994 or so, has been having some problems.

The picture and sound are fine, but more often than not, after 20 or 30 minutes, the picture compresses vertically to almost a 16:9 ratio. A stout whack fixes it right up. I'm getting pretty tired of getting up and whacking it every 20 minutes, so I was wondering if this is fixable? It's also pretty sensitive to stomping and whatnot. For example, jumping around the TV makes the image jump vertically.

I took it apart (bear in mind, I don't know what I'm doing) and saw that it was dusty beyond recognition. So I set to work trying to clean up everything with about a million moist Q-tips. After two hours or so, I got most of the obvious patches of dust clean, but there's still some parts that have plenty of dust, mostly around capacitors and hard-to-reach places and such.

While it was open, I noticed a few pots, two labeled 'screen' and 'focus'. I didn't touch them.

I couldn't find a service manual, so I was wondering if you guys could help?

I guess I could just keep on whacking it. I really like this television and would love to have it keep working.

Thanks all, and sorry if this is in the wrong section.
 
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try compressed air for cleaning out the dust .
most problems stem from the h.o.t . "horizontal output transistor " and the flyback transformer . that's the one with a lead going to the side of the crt "picture tube " p.s don't touch the lead or anything else for that matter even whilst turned off . electric shock hazard ..
going from you diagnosis you have a bad contact somewhere . try pull off connector plugs and put back on to clean them . also look for a dry joint by the flyback transformer plus the h.o.t . it is a biggish transistor right by it .also try pull the circuit board on the rearmost of the picture tube and put it back .
if it has lots of dust inside it can lose lots of power through it . my uncle worked out the loss for me when i was about 12 and learning.. .tv.s were black and white and full of tubes back then mind .
don't touch the pots until stable .. screen is voltage to screen .focus is obvious . you may need to adjust them both slightly . i would make a tool though out of plastic .. like i say high voltage around the flyback .
 
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Rich: Wow, I didn't even know that site existed. Since I already started here, I'll just finish up here. If this bothers anybody, please let me know.

Pete: I'll try compressed air to clean out the dust (of which there is an unreal amount might I add, where did it all come from?!).

On the right side of the board, I see the letters 'H O T' in big letters, is that it?

I don't see anything going into the side of the tube, but I see a big 'heart monitor' patch going into the top of the tube.

Thanks for the advice. I'll reseat any of the connectors I can find. There's one connector going from the circuit board to the actual tube, maybe that's the one?

I'll try that. Next time I take it apart, I can take some pictures if you like, will that help?

I don't think I can take out the board at all as it's connected to the buttons, which are on the front and right under the tube.

Thanks all.
 
You do know that there's potentially deadly voltages in there even with it turned off and unplugged? Stay away from the heart monitor patch thingy.:nono:
 
if you could post pictures it would help . . the mainboard should unscrew and pull out enough to work on it . that's what i always found anyway . just don't go near that lead that goes to the tube it can and will bite you even through its insulation .
 
Jesus, maybe I should've asked here before taking it apart. I cleaned the heart monitor patch thingy with a moist Q-tip. :sigh:

I'll clean out the dust and reseat the connectors tomorrow, as I don't have compressed air available right now. I'll take pictures then as well. Should I take pictures of anything specifically?
 
Any internal adjustments labelled "vertical height" or "V. Height"? It could be a dirty potentiometer.

If it's sensitive to vibration, try (CAREFULLY) poking around a bit to localize the sensitive area.
 
unlikely to be any adjustment in a modern set . maybe wrong though ..
a good to excellent site is here ..http://www.avrepair.info/ . its helped me a lot in the past ...its been a while since i looked at a crt set .
you need to find out the mainboard manufacturer ,,a popular one is vestel
 
Alright, I just took it outside and cleaned all the dust out. After bringing it back inside, I turned it on. For the few minutes it was on, it didn't compress, but it's still very sensitive to any kind of vibration (whacking it, walking around it, etc.). I tried to reseat the connector I had found, but couldn't get it out, so I didn't risk it.

I also took some pictures for you guys, so maybe that will help. I didn't find 'vertical height', but I did find 'V-SIZE' (Image 62). I also took some pictures of the mainboard, including the 'H O T'.

What should I do now?

At least it doesn't compress within the first few minutes now.

Thanks all.
 
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Outland said:
Alright, I just took it outside and cleaned all the dust out. After bringing it back inside, I turned it on. For the few minutes it was on, it didn't compress, but it's still very sensitive to any kind of vibration (whacking it, walking around it, etc.). I tried to reseat the connector I had found, but couldn't get it out, so I didn't risk it.

I also took some pictures for you guys, so maybe that will help. I didn't find 'vertical height', but I did find 'V-SIZE' (Image 62). I also took some pictures of the mainboard, including the 'H O T'.

What should I do now?

At least it doesn't compress within the first few minutes now.

Thanks all.
Click to expand...

good pics. yank the plug and pull the board all the way out. flip it upside down. etching side up. look for bad solder connections. looks like its silk screen on the component side. so look for the vertical out amp. check for bad conns around there. luck
 
as above ..if that fails mark the vert size pot and rotate it back and forth a few times and put back to the mark .
 
Oh wow, I don't think I have the care needed to take out the board without touching the heart monitor. Maybe I should take it to a professional tech? Jesus, who works on CRT televisions these days.

I tried messing with the V-SIZE pot but it didn't seem to do much of anything.

One thing I noticed is that it only jumps if the vibration is 'vertical'. For example, if I whack it on the top, it jumps like crazy even from light tapping. If I whack it on the side however, nothing happens. Does that mean that it's connected with the flyback thingy (which is right under the top plastic case, the circuit board is on the bottom)?
 
This is where you might put a mirror in front of the set, so you can see it from behind. Then you use something non-conductive, like a wooden dowel or something along those lines, and tap around different areas of the set to see if you can isolate where the impact is having an effect. If that's not something you're comfortable doing, then don't do it.

If you're not familiar with CRT sets and their high-voltage sections, then you most definitely avoid that area you mentioned that was marked as HOT. And don't stick your hands in there with the set on. Or even off, for that matter. As others mentioned, high voltages persist in CRT sets.

Edit: As a matter of fact, you don't really want to stick your hands anywhere with the set even PLUGGED IN. Most televisions have areas of the power supply that are HOT - i.e., not isolated from the AC line.
 
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Outland said:
Alright, I just took it outside and cleaned all the dust out. After bringing it back inside, I turned it on. For the few minutes it was on, it didn't compress, but it's still very sensitive to any kind of vibration (whacking it, walking around it, etc.). I tried to reseat the connector I had found, but couldn't get it out, so I didn't risk it.

I also took some pictures for you guys, so maybe that will help. I didn't find 'vertical height', but I did find 'V-SIZE' (Image 62). I also took some pictures of the mainboard, including the 'H O T'.

What should I do now?

At least it doesn't compress within the first few minutes now.

Thanks all.
Click to expand...


Yes, V-size is what I meant to say. V-height is stupidly redundant now that I think about it.
 
adam-ads said:
Yes, V-size is what I meant to say. V-height is stupidly redundant now that I think about it.
Click to expand...

Yeah, I think 'size' and 'height' were used interchangeably. The other pertinent vertical controls that might be available were 'position' and 'linearity'.
 
Adjusting the vert size isn't your problem.

It would be a good to let a technician work on the set if you are a novice. First and formeost you could harm yourself. Playing around with pots just to see what they do is not a good idea either.

Cold solder joints are fairly common issues with newer CRT sets.Could also be power supply related (caps maybe).

If you haven't done so, try going to Videokarma and post your problem in the Rectangular Tube & Solid State forum. You may get some advice or they may be able to steer you to a good repair shop.
 
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