Whats the best way to run a set and remove the high voltage ?

[kramden66]

Have to touch up the sound and can't get to the adjustments without risking contact with the metal cone of the crt , so what is the best way to run the set and remove the voltage ?
do i just remove the 1B3 and it is safe to run the tv that way or do i remove other tubes ?
mike

[N2IXK]

Pulling the 1B3 is probably best, as it will disable ONLY the HV, not the horizontal sweep. Make sure the 1B3 plate lead is well clear of anything (including the tube socket), so it doesn't arc over. You don't actually need to remove the tube, just disconnecting the plate cap is sufficient, as it will keep the 1B3 filament load on the flyback.

Pulling the horizontal output tube as many recommend removes a substantial load from the B+, and will also kill the boost voltage. This may cause a problem for other circuits in the set.

[kramden66]

thanks

[NoPegs]

Originally Posted by kramden66

thanks

You could also just pull the anode lead and put a bottle over it...

[Tubejunke]

Originally Posted by NoPegs

You could also just pull the anode lead and put a bottle over it...

Now there's a workable idea that I bet few people would have come up with. Ultimately I would feel better removing the plate cap of the h.v. rectifier(s) as God forbid that bottle move and snap crackle pop with your head in the cabinet! The only DuMont I ever had bore 2 l.v and h.v. rectifiers which is why I referenced 2 of them.

[cwmoser]

I've always pondered on this question too thinking it would be nice to
not have that HV when working on other circuits. I have a Philco 48-2500
that appears to have an RF issue that I'm stumped on. I might try removing
the 1B3's to avoid potential radiation and HV issues. BTW, no chance of shock
touching that glass jar when power is removed?

Carl

[Username1]

Remove plate cap, or be very careful and wear good insulating gloves.

If you absolutely have to run it with no picture tube attached, and I can't think of
any reason where that is the only option, I would attache the HV wire to a hv probe
like a voltage probe, and tape it off and put it inside a bicycle tube or similar rubber
protection boot. That way you have a load of some kind, you don't want that voltage spike
reflecting back onto the primary of the HVT.

.

.

[miniman82]

Why leave the horizontal section running at all? Pull the horizontal output tube and damper, 100% safety.

[cwmoser]

Originally Posted by miniman82

Why leave the horizontal section running at all? Pull the horizontal output tube and damper, 100% safety.

So, just pull the Horizontal Output Tube and Damper Tube?
Should the 1B3 be pulled to?

This bearing in mind that the B+ might be somewhat unloaded.

Carl

[N2IXK]

If you pull the HOT and damper, then no need to pull the 1B3, as it won't be seeing any plate or filament voltage.

But as you say, this will take a significant load off of the B+. This will increase voltages throughout the rest of the set, and will kill the boost voltage, which is needed in some sets to run things like vertical sweep.

When doing an alignment or other critical adjustments, you want the set in as close to a normal operating condition as possible. The least "invasive" way to disable HV is just to disconnect the 1B3 plate cap.

[old_coot88]

Originally Posted by N2IXK

...This will increase voltages throughout the rest of the set,

...and will kill the boost voltage, which is needed in some sets to run things like vertical sweep.

Not to mention AGC keying pulse (though it's doubtful the set under discussion has keyed AGC).

[NoPegs]

Originally Posted by Username1

Remove plate cap, or be very careful and wear good insulating gloves.

If you absolutely have to run it with no picture tube attached, and I can't think of
any reason where that is the only option, I would attache the HV wire to a hv probe
like a voltage probe, and tape it off and put it inside a bicycle tube or similar rubber
protection boot. That way you have a load of some kind, you don't want that voltage spike
reflecting back onto the primary of the HVT.

.

.

Bicycle tubes are conductive. Well, at 10kV and up they're not good at insulating, under 250v they're fine. Just letting everyone know.

Concrete is conductive too!

[Phil Nelson]

Originally Posted by cwmoser

BTW, no chance of shock touching that glass jar when power is removed?

I have taped the 2nd anode lead inside a jar a bunch of times. The jar won't shock you. Glass is a fine insulator.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[cwmoser]

[QUOTE=Phil Nelson;3117637]I have taped the 2nd anode lead inside a jar a bunch of times. The jar won't shock you. Glass is a fine insulator.

Just double checking that we are not making a "glass jar capacitor" :-)

[old_coot88]

Originally Posted by cwmoser

Just double checking that we are not making a "glass jar capacitor" :-)

Not unless you line it inside and out with foil.. whut would be a Leyden jar.