Sony PVM spot killer circuit

[Initial-d]

Could any one possibly highlight the 'spot killer' circuit for a Sony PVM-20L4 as I get some interesting patterns from the RGB during shutdown, they move and fade in a couple of seconds, but I would prefer the white raster during power off. I've looked over the schematics but its way beyond my cap swap expertise! I expect it is a cap, but short of swapping everything on the board I don't know where to start tbh.

If someone could point me in the right direction it would be so helpful, I ask Pat in the US about it but haven't heard back.

[Dochartaigh]

Could any one possibly highlight the 'spot killer' circuit for a Sony PVM-20L4 as I get some interesting patterns from the RGB during shutdown, they move and fade in a couple of seconds, but I would prefer the white raster during power off. I've looked over the schematics but its way beyond my cap swap expertise! I expect it is a cap, but short of swapping everything on the board I don't know where to start tbh.

If someone could point me in the right direction it would be so helpful, I ask Pat in the US about it but haven't heard back.

You're talking about the kinda cloverleaf (~4x circles) rainbow pattern which happens when you turn off the PVM? Just making sure you know this is pretty normal behavior... at least in the ~8ish+ similar 800TVL 14/20M4's and 14/20L5's I've owned (couple which were supposedly backup units and rarely if ever used).

I do remember somebody posting a 'fix' (possibly a slight tinkering/redesign of the original circuit to be different than it was originally engineered) on one of the FB groups I'm on, but do not remember what exact part it was (want to say the neckboard, but I could be totally off).

[Initial-d]

Yeah that's the RGB pattern, RGB moving outward it briefly looks like, I have a 20M4 and a 20M2 which don't do it, just a white flash and fade.

I had a 20L4 a few years back but can't remember it doing it. Would be interesting to see the possible mod for it if you by any chance can locate it. Good to know its not a big issue at least, phew!

[Dochartaigh]

Yeah that's the RGB pattern, RGB moving outward it briefly looks like, I have a 20M4 and a 20M2 which don't do it, just a white flash and fade.

I had a 20L4 a few years back but can't remember it doing it. Would be interesting to see the possible mod for it if you by any chance can locate it. Good to know its not a big issue at least, phew!

FB search sucks SO bad... but if you join the "Professional & Broadcast CRT Monitors" group and search for "Rainbow" you can find some posts on it.

Also seems like when they flash white - that could very well be an issue which WOULD be good to look into (not to worry you... just some comments about that being the bad behavior, not this rainbow one perhaps).

Also found a post that I forget even making lol, but ~3 years later a guy I sold a 20L5 to, with the rainbow, and his is still going great... so not something I personally worry about.

[Initial-d]

Thanks for the tigon the FB group I'll join and take a look.

Interesting about the shutdown aspects rainbow vs white flash. I'll look into it more.

[Dochartaigh]

Thanks for the tigon the FB group I'll join and take a look.

Interesting about the shutdown aspects rainbow vs white flash. I'll look into it more.

Just approved you for that FB group (if that was you, mentioned 20L4...) so you can search now, and if you find anything relevant please post here as well so the information is more out there for all!

[Initial-d]

Thanks for the tigon the FB group I'll join and take a look.

Interesting about the shutdown aspects rainbow vs white flash. I'll look into it more.

Just approved you for that FB group (if that was you, mentioned 20L4...) so you can search now, and if you find anything relevant please post here as well so the information is more out there for all!

Thanks! Yes that was me

[matt]

My 20L5 does that, I'm not especially worried since the beam is pretty diffuse at that point and doesn't seem likely to burn a spot in the tube (which is what the spot killer circuit is supposed to prevent).

Personally, I think it's probably a tube issue vs a chassis problem. I've seen this pattern appear in tubes (not Trinitrons) shortly after rejuvination. Also, I once had a Samsung monitor that showed this pattern. I swapped the tube into another monitor and the rainbow pattern persisted on the new chassis.

The real test would be to do a tube swap between a rainbow shutdown PVM and one that doesn't. But I don't feel like it's important enough for me to take apart my L5 just to find out.

[PleGuS]

Matt is right. I had a 14M4U with the rainbow problem during shutdown, everyone thinks it is due to a malfunction of the spot killer (and it is true) but not due to a defective electronic component such as an IC or a capacitor. The problem with the spot killer not working is due to a short in the tube. The barrels are slightly shorted due to residual carbon from the cathode. This, apart from generating the rainbow effect on shutdown, normally ends up lifting a color over the black, obtaining a slightly greenish or reddish or bluish black. It starts with a very subtle tone and gradually increases with the use of the monitor. There are two solutions: 1. Replace the tubi CRT, this I did and the problem was completely solved. 2. Use a tube rejuvenator in short clean mode, risky but sometimes effective. Anyway, that rainbow is a symptom of an aged/short tube.

[Initial-d]

That’s good to know the cause, thanks for the detailed explantion.