20" round tube DuMont on the 'bay

[Tom Albrecht]

Bill,

Sure - that would be great to have pictures of. I'll send you a PM with my email address.

Tom

[pallophotophone]

Originally Posted by bandersen

Wow! The winning bid was $932! Wonder who got it

Oh what the heck- I won it.

It's my only Dumont, I presently had a little loose funds, and I'm glad I have it, come what may.

And since it's just down the thruway from me in Syracuse, I won't have to worry about shipping costs or worse- damage.

Hope I can bring it back to life eventually. A little elbow grease should help the appearance for now.

Bob Hodge

[John Folsom]

Way to go, Bob! Hope that 20BP4 is AOK.

[Tom Albrecht]

If that 20BP4 turns out to be bad and you are interested in rebuild... I have a 20BP4 which is bad that I want to rebuild at RACS in France. Shipping is very expensive (as is the rebuild), and pooling several of these large Pyrex tubes in a common shipment would save each person hundreds of $.

Shipping within the U.S. by FedEx Ground is very cheap. The problem is overseas shipping, and that is where we can save by pooling. So we should ship within the U.S. to one location and send combined to France by overseas freight.

I've mentioned this on many occasions, and I'm reasonably patient to wait for a plan to come together, but I don't want to wait for ever...

[pallophotophone]

Originally Posted by Tom Albrecht

If that 20BP4 turns out to be bad and you are interested in rebuild... I have a 20BP4 which is bad that I want to rebuild at RACS in France. Shipping is very expensive (as is the rebuild), and pooling several of these large Pyrex tubes in a common shipment would save each person hundreds of $.

Shipping within the U.S. by FedEx Ground is very cheap. The problem is overseas shipping, and that is where we can save by pooling. So we should ship within the U.S. to one location and send combined to France by overseas freight.

I've mentioned this on many occasions, and I'm reasonably patient to wait for a plan to come together, but I don't want to wait for ever...

Thank You, John and Tom !!

And if it needs to be rebuilt, I'll keep your offer in mind! Any idea of the cost of the rebuild? Could it be rebuilt if it has gone to air?

I will have a tempered moment of rejoicing if the getters are still good.

Very Cordially Yours!!

Bob

[leadlike]

I'm curious-with the larger crts, did they take the same gun as what went into a 10bp4, for instance? If so, did that mean the 20" tube would wear out faster as the cathode had to emit more material to cover the larger screen area?

[jr_tech]

Voltage as well as current density affect brightness, so if the larger tube is run at a higher voltage, decent brightness could be produced without increasing cathode "loading". There is a limit to this, however, especially in un-aluminized crts.

jr

[Tom Albrecht]

RACS rebuild is somewhere in the 750 Euro range for a Pyrex 20BP4. I was hoping people would get mobilized earlier this year while the dollar was strong so that the price wouldn't be so high in dollars, but alas that didn't happen and the dollar is falling now. So that's about $900-1000 at the moment for the rebuild.

RACS does a full rebuild with new phosphor and aluminization, so there is no problem with rebuilding tubes that have gone to air.

Shipping, if you try to ship just one tube yourself, is somewhere in the $600 - $1000 range. That's why we have plenty of incentive to pool. The total shipping price will be the same, pretty much regardless of the number of tubes, since it will be an overseas surface freight shipment on a pallet. It will be cheaper if we pool our tubes and ship from the east coast or Great Lakes region, rather than the west coast.

Obviously this isn't cheap, but if you have a valuable Pyrex tube to rebuild, it's the only game in town -- or more precisely, in the world.

[Tom Albrecht]

That's probably a matter of taste. I'll probably go with aluminized, but one could presumably have the option to choose no aluminization and bent gun for more historical authenticity.

[jeyurkon]

Originally Posted by Tom Albrecht

That's probably a matter of taste. I'll probably go with aluminized, but one could presumably have the option to choose no aluminization and bent gun for more historical authenticity.

Or, you could go for aluminization and bent gun. Some other CRTs were done that way for increased brightness, such as the 12LP4C. It still required a double field magnet.

The lower cathode current might mean longer life. Especially for a larger CRT like the 20BP4. Given the expense of rebuilding one that might be desirable.

John

*** Oops! Chuck pointed out that the 20BP4 is a straight gun to begin with. ***

[ChuckA]

Originally Posted by Tom Albrecht

That's probably a matter of taste. I'll probably go with aluminized, but one could presumably have the option to choose no aluminization and bent gun for more historical authenticity.

Tom,

20BP4 is a straight gun, it's a screen burner. All of mine show ion burns on the screens.

Chuck

[Tom Albrecht]

Mine has a big blast spot of missing phosphor in the center, so I think I never had an opportunity to notice the ion burn!

Aluminized sounds like the way to go.