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

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

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.

thanks

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.

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

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.

.

.

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

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.

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

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!

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

[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" :-)

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

I don't think there is any issue with allowing the HV supply to run with no load. In normal operation with CRT connected, if you turn the brightness down to the point the picture is black, there is no load on the HV. I'm sure none of us would think of turning the brightness down as something that would harm a set, so I would not be concerned about running the set with the HV active, but disconnected from the picture tube.

Running it into a HV probe can be nice simply to keep an eye on things, but it's not necessary.

A glass jar as an insulator is good. Usually I simply prop the lead in a manner that the end is not close to anything, but it is a bit precarious that way.

While working on a CTC-11 RCA color set I disconnected the plate cap from the 3A3, then wrapped two layers of black tape around it, being careful to not pull on the cap or the flyback connections. The sweep sections and the neck components remained in-circuit with the power supply only "up" by a few volts due to the CRT not drawing HV current. Did what I had to do, carefully removed the tape, and hooked it up again, and all was OK. Might not be the best method for all. I DO like the HV lead in plastic or glass, too.
All the best!!!
Kevin

like Username1 suggested, i just hooked up the hv wire to a hv probe and kept it a distance from anything-just rested the connection on a piece of plastic-worked well over the years.