CRT monitor gone AWOL(please help)

[stj]

Re: CRT monitor gone AWOL(please help)

i dont know how it damages diodes, i just know it can because i'v seen it.

the 2-screwdriver or crewdriver & wire with crock-clip trick goes back to b/w and probably valve days.
it was always a bodge for people without a high-voltage probe.

[budm]

Re: CRT monitor gone AWOL(please help)

that stupid trick can damage diodes in the lopt.

if you need to discharge a tube, get some 1meg high voltage resistors and solder them in series , put them in something like a plastic pipe for safety with some high-voltage wire coming out of each end to short under the cap with.

How? I don't see how the diodes can be damaged, you are not discharging through them or anything - worst I can imagine is arc damage to the anode connector\screwdriver, but please tell me if there's something I've missed!

Of course one should use the proper tool, but this thread is about a crusty old 17" CRT that's been outside for 2 years...

i dont know how it damages diodes, i just know it can because i'v seen it.

the 2-screwdriver or crewdriver & wire with crock-clip trick goes back to b/w and probably valve days.
it was always a bodge for people without a high-voltage probe.

That is funny, I worked on thousands of CRT TVs (100% tube and SS) and CRT monitors in my life time. RCA, ZENITH, PHILCO, MAGNAVOX, QUASAR, CURTIS MATHIS, SONY, PANASONIC, MITSUBISHI, WELL-GARDNER, JVC, iiYAMA, NEC, Viewsonic, KDS, etc. and never once damage the Voltage multiplier on the FBT.
RCA supplied us Plexiglass rod with sharp metal tip at the end which attached to the drain ground wire with alligator clip at the end.
It is just B.S. to me. It is funny to hear these kind of stuff from younger generation.
No you did not miss anything.
It is like saying you will damage the rectifier when you discharge the filter caps in the power supply, it is just high Voltage power supply.
Do you damage the rectifier when you discharge the filter caps? NOPE! CRT is just a big high Voltage cap.
BTW, you have to discharge it more than once.

[kaboom]

Re: CRT monitor gone AWOL(please help)

BTW, you have to discharge it more than once.

Yes you do! Dielectric absorption.

It's also a very good capacitor- just rubbing the front of a disconnected CRT with a towel, in dry weather, can charge them up a little.

I've always discharged the anode to the DAG GND. Never blew diodes in the multiplier/rectifier or focus/screen block.

[stj]

Re: CRT monitor gone AWOL(please help)

moving on, do we have a schematic to isolate the psu section?

[budm]

Re: CRT monitor gone AWOL(please help)

Gateway 2000 VIVITRON full model number?
CPD-??????
I.E.:
http://www.ecrater.com/p/14542471/ga...monitor-17-cpd ??????

We need good clear pictures to see what condition of this monitor is.

[stj]

Re: CRT monitor gone AWOL(please help)

looks a bit like a sony.

[momaka]

Re: CRT monitor gone AWOL(please help)

^ Well it is a Vivitron... hint hint hint .

Seriosuly, at this point, we need pictures to troubleshoot the monitor. The OP seems inexperienced (sorry TechGeek, no offense here) so a schematic won't do as much good IMO...

And no, plugging in the monitor again and filming a video won't be any good either, unless you just want to finish burning it up and throw it away after that.

See this thread and use the incandescent bulb trick next time before you power it on:
https://www.badcaps.net/forum/showpo...4&postcount=70

As far as discharging the tube - that likely isn't necessary as Trinitrons have a built-in discharge mechanism. That said, if you will be removing the anode cap to get the boards out, then do try to discharge it, just in case. I usually use the aligator clip and screwdriver trick, but with one addition: I have a 4.7 KOhm 5W resistor to limit the current so that I don't get a huge spark. You don't need to have exactly that kind of resistor. Any resistor that is 1 KOhm or more and rated for at least 1W of power or more will do. But again, this is not necessary. As agent_24 noted, it's a "crusty" 17" CRT .

The thing you should be most worried about is the large bulk cap on the input. That one can store 170V to 340V (depending on your line voltage, but since you are in the USA, it would be the former). You definitely don't want to touch its leads or anything that is connected to them. It likely won't kill you, but it will hurt enough to remember it, especially if you discharge it through your entire body (i.e. current entering through one hand and exiting through the other). I discharged those kind of caps through my thumb a few times before and IT HURTS! Best case it will feel like a nasty bee sting. Worst... it hurts okay.
So anyways, as you are taking the board out, avoid touching the primary side or any components on it. Better yet, if you can discharge that bulk cap before you begin taking out the board, that would be even better.

I myself was working today on a 17" Sony CRT with a PSU problem. Will be discharing the bulk cap tomorrow before pulling out the boards. There's a way, but you need to know what you are doing. And without pictures, I can offer you zero advice on that.

[TechGeek]

Re: CRT monitor gone AWOL(please help)

I'll try to get good pictures tomorrow.