CRT Maintenance and Adjustment

[maxtherabbit]

Over this past weekend I've been reading everything I can get my hands on regarding CRT work. So far I've really only had some sparse luck on google and primarily my main resource has been a PDF and gray117 was kind enough to link me.

http://www.arcaderepairtips.com/wp-cont ... v1.2.0.pdf

It would really do this community a huge amount of good if there was a wiki or similar resource devoted to these things, because it has become an arcane art. Any search you do on google inevitably just tells people to not try to do anything to their CRTs because of shock danger. Yes, safety is important, but summarily discouraging everyone from learning in the name of safety is counter-productive.

Personally, I've recently gotten up to speed on how to safely ground the anode to the braid. It's not terribly complicated. I have thus far been cautious, probably overly so in poking at my CRTs.

I know retrorgb and others have discussed creating a retro gaming wiki recently, and it would be wonderful to devote a section of that to CRT repair and adjustment. Start people off with a safety primer and then go from there.



So the questions that I have so far from my limited experience:
1) as long as you don't need to touch the anode or the flyback, is there any reason to discharge the tube prior to work?
2) other than mains voltage, what areas specifically are unsafe to contact? is it safe to touch the yoke and neck board (with a charged tube) without gloves?
3) (more specific to my situation) I picked up another trinitron for free saturday, this one just has a bit of horizontal bow that's uniform through the image. I found that by gently prying the top of the yoke away from the tube, I can correct this. Is it safe to simply shim it into the adjusted position without loosening the neck clamp? or is that risking unsafe pressures applied to the neck or yoke over time?

Help me and everyone else make CRTs great again! Thanks

[thebigcheese]

If you (or anyone else) wants to add a section to my wiki, I'm all for it. I also found little to no information about it and that's a big part of the reason I have mostly given up on using my PVM. Even the guy I tried to hire who supposedly fixes and calibrates TVs didn't know what to do with it. I know absolutely nothing about it, but if someone starts a few pages we can figure out what's the best way to add it to the main navigation. www.retromodwiki.com. I am thinking there will be a "CRTs" drop-down, then I'm not really sure what would be in the list from there. I suspect a separate page for each model would be useful, though perhaps a bit overkill. That way we could have service manuals and other model-specific info on the page instead of just having a big list of manuals somewhere. Maybe instead of individual models, could group all models covered by a single service manual onto one page as they would likely have similar info.

[maxtherabbit]

If you (or anyone else) wants to add a section to my wiki, I'm all for it. I also found little to no information about it and that's a big part of the reason I have mostly given up on using my PVM. Even the guy I tried to hire who supposedly fixes and calibrates TVs didn't know what to do with it. I know absolutely nothing about it, but if someone starts a few pages we can figure out what's the best way to add it to the main navigation. http://www.retromodwiki.com. I am thinking there will be a "CRTs" drop-down, then I'm not really sure what would be in the list from there. I suspect a separate page for each model would be useful, though perhaps a bit overkill. That way we could have service manuals and other model-specific info on the page instead of just having a big list of manuals somewhere. Maybe instead of individual models, could group all models covered by a single service manual onto one page as they would likely have similar info.

I'd be happy to help out, but my knowledge is pretty limited. Would be really awesome if we could get some vet arcade tech(s) to dump some knowledge and then let us sort it out

[Syntax]

You seem like you need to know much more than one thing.

I highly suggest spending $10 on a crt repair book.

I went looking for a link to one for you ( I purchased mine from WES components but without an account I cant show you)

But all I found was this crt repair seminar breakdown
http://www.noahtechelectronicstraining. ... onitor.pdf

Bet a few of us would of could of done with being there that day

[BONKERS]

This is a great idea.

I've got 2 VGA CRTs and a flat tube 27" 15khz Phillips CRT (Which needs to be cycled on and off fairly often when used or at least used to. As one section of the screen would get heavily discolored and needed to be degaussed) and I would love to make some adjustments.
I've seen the focus pots on the inside of one of them. But i'm deathly afraid to make other adjustments.

I've heard that using magnet strips placed along the tube in places can help out with geometry, but again kind of afraid to try.

[Syntax]

This is a great idea.

I've got 2 VGA CRTs and a flat tube 27" 15khz Phillips CRT (Which needs to be cycled on and off fairly often when used or at least used to. As one section of the screen would get heavily discolored and needed to be degaussed) and I would love to make some adjustments.
I've seen the focus pots on the inside of one of them. But i'm deathly afraid to make other adjustments.

I've heard that using magnet strips placed along the tube in places can help out with geometry, but again kind of afraid to try.

Do you have a magnetic tipped insulated screwdriver?
Wrap some tape on the steel so you don't scratch the tube and roll it around the back of the tube, working your way from out to centre, to see what effect putting magnets in different spots will do.

Its the way I test before adding magnets to fix geometry

[maxtherabbit]

You seem like you need to know much more than one thing.

I highly suggest spending $10 on a crt repair book.

I went looking for a link to one for you ( I purchased mine from WES components but without an account I cant show you)

But all I found was this crt repair seminar breakdown
http://www.noahtechelectronicstraining. ... onitor.pdf

Bet a few of us would of could of done with being there that day

my immediate need is to know if it's ok to shim the yoke without reseating the clamp

Beyond that, yes I'd like to become fully versed in the trade. Not opposed to buying a book by any means, but I still think an online resource would benefit the community greatly

[Syntax]

The plastic on the yolk will crack before the tube will.
Decide with your ears should be fine though.

[Makinx]

These are pretty good online resources about CRT's with a lot of in depth info:
https://www.repairfaq.org/sam/crtfaq.htm
https://www.repairfaq.org/sam/deflfaq.htm

[maxtherabbit]

The plastic on the yolk will crack before the tube will.
Decide with your ears should be fine though.

awesome, thanks!

These are pretty good online resources about CRT's with a lot of in depth info:
https://www.repairfaq.org/sam/faq.htm
https://www.repairfaq.org/sam/deflfaq.htm

first link 404d, but the second one is good

I'll read over it asap, thanks

[Makinx]

Yeah I screwed up the first link. I fixed it now.

[eccoboy]

I think you should discharge anytime the case is removed. It’s easy to do and no reason not to unless you are doing minor adjustments and know what you’re doing.

Service manuals have a lot of information but I think you need to understand the problem and how to address it before the service manual becomes useful. So yes, a general guide would be helpful.

Another concern is the availability of parts. Even with the skills to repair, are all the parts going to be available for your particular model?

[maxtherabbit]

I think you should discharge anytime the case is removed. It’s easy to do and no reason not to unless you are doing minor adjustments and know what you’re doing.

Service manuals have a lot of information but I think you need to understand the problem and how to address it before the service manual becomes useful. So yes, a general guide would be helpful.

Another concern is the availability of parts. Even with the skills to repair, are all the parts going to be available for your particular model?

the charge stored in the aquadog of the tube body is only dangerous upon contact to the anode or flyback, correct?

[eccoboy]

I don’t know, but I would assume that the charge is present at multiple points on the board. Someone else could provide details. I don’t know why you wouldn’t just discharge properly and not worry about it.

[maxtherabbit]

here's a tangential thought: AFTER properly discharging a tube, if you intended to leave it disassembled for an extended period, could you connect a jumper from the anode terminal on the tube to the chassis to keep it from building charge from the earth's magnetic fields etc.?

[eccoboy]

building charge from the earth's magnetic fields etc.?

What?

[Syntax]

Lol, Earths magnetic field charging your TV? Recon I can charge my phone off it?

Not being rude but that's a bogus idea and shows you need to read a bit more about electronics in general.

Seriously though, the anode builds charge back up because the caps dont fully discharge when you ground them.
You have to go back a few times before they are fully drained.

[maxtherabbit]

Lol, Earths magnetic field charging your TV? Recon I can charge my phone off it?

Not being rude but that's a bogus idea and shows you need to read a bit more about electronics in general.

Seriously though, the anode builds charge back up because the caps dont fully discharge when you ground them.
You have to go back a few times before they are fully drained.

yeah I thought it sounded dubious but voultar said it on the retro roundtable last night

not my own idea, and to be quite honest I don't care to learn enough about physics to be able to refute or prove the claim

I've been working on electronics for decades and never really had cause to give a fuck about geomagnetism before, so forgive me for believing a guy who seems legit

[Syntax]

I didn't watch round table but he was probably referring to geomagnitism effecting the electron guns in a crt.

Later crts had a gravitation field elimination circuit consisting of 2 identical coils around the neck tube.
When charged they create a field that overrides the earth and cancels each other out at the same time giving the electron guns a controlled environment to work in.

You can check if your tv has the coil by rotating it while it's on and seeing if the picture rotates.
Some will even lock color to the direction the tv was last degaused in.

[maxtherabbit]

I didn't watch round table but he was probably referring to geomagnitism effecting the electron guns in a crt.

Later crts had a gravitation field elimination circuit consisting of 2 identical coils around the neck tube.
When charged they create a field that overrides the earth and cancels each other out at the same time giving the electron guns a controlled environment to work in.

You can check if your tv has the coil by rotating it while it's on and seeing if the picture rotates.
Some will even lock color to the direction the tv was last degaused in.

no he specifically said fields can charge a discharged tube, discussion was tube safety not geometry or convergence

again I'm not cosigning it, I don't understand physics - like take inductance for example: I know it exists and how to use it, but if you asked me to explain how current flow in two separate conductors can interact, I would probably say magic

[ChuChu Flamingo]

Calibrations and Yoke Adjustments would be great, especially the latter since you need to do it while powered on to fix tilted geometry. All the videos I've seen don't really show it done live, only the results.

I am surprised it took this long for people to start asking for a wiki. There is a lot of misinformation out there ranging from dual wielding two screw drivers and crossing them to discharge (lol), touching the red anode wire before confirming it is fully discharged is kosher because rubber never ever never cracks, and my favorite is licking the chip ics to find where the rgb points are.