CRT experts please

[stromberg6]

Perhaps there is a filter cap in the high voltage cage under or around the 1B3. Agreed that it's strange that other tubes of that type have aquadag and yours doesn't. Only had one Muntz in my life, and it was a later model with a 21" tube, a two IF urban special. What's your model or chassis number? Maybe someone with Rider TV books or SAMS can look it up to find out how it was configured. Good Luck! Sounds like an interesting challenge.

[stromberg6]

Just found this online. It says that there is supposed to be a coating. Hope it helps!
Kevin

[radio nut]

Originally Posted by stromberg6

Perhaps there is a filter cap in the high voltage cage under or around the 1B3. Agreed that it's strange that other tubes of that type have aquadag and yours doesn't. Only had one Muntz in my life, and it was a later model with a 21" tube, a two IF urban special. What's your model or chassis number? Maybe someone with Rider TV books or SAMS can look it up to find out how it was configured. Good Luck! Sounds like an interesting challenge.

Yes there is a high voltage cap below the high v rectifier...... Like you, I too looked up the 16rp4 specs and yes it shows a coating....

But this muntz is working....no coating on crt or grounding strap.........no where on chassis...now what. use another crt and put my own grounding strap on or what. I will recheck what model number it is and post it here.I just dont know which way to go,The set works well but the crt is weak and has the classic "indian" test pattern burned onto the screen....... So I would like to do something

[earlyfilm]

Originally Posted by radio nut

. . . the crt is weak and has the classic "indian" test pattern burned onto the screen. . . . .

Sheesh! I don't think I've ever seen test pattern burns except on TV station monitors, and no TV station would use a Muntz!

(Well, I once worked at a TV station that had Crosley monitors in the Lobby, but WLW-A, now WXIA, was owned by AVCO at the time, and boy, did they go away the moment the station was sold.)


On the conductive coating, a more logical guess is that someone cleaned off the old flaking paint not realizing that it was part of the tube.

However, I've seen a few rebuilt CRTs that had an external conductive coating where one was not specified (and if they do, you must fabricate a ground or it will bite you) and much more commonly, a new-out-of-the-box rebuilt CRT that was missing the coating.

A peculiarity of the CRT that you have is both the 16RP4 and 16RP4A require an ion trap while the 16RP4B does not! Back in the late 50's I replaced a CRT, I can't remember the tube number, but it was an all glass B&W roundie, where this tripped me up, and the rebuilt tube actually looked dimmer than the one it replaced until my boss removed the old ion trap that I had transferred to the new CRT! I felt like an idiot for not catching this, and he never let me forget it. I noticed the ion trap never had a brightest spot, even if reversed, and that should have been a clue, but I slept through it.

James

[earlyfilm]

Originally Posted by radio nut

. . . . . . . . . . .Yes there is a high voltage cap below the high v rectifier . . . . . . . . .

The most common basic 1951 Muntz chassis was used in set model M31 and a bunch of other adjacent numbers indicating cabinet variations . The M31 schematic in Beitman's 1951 page 101 does NOT show a 500mmF underneath the 1B3, but it does show an aquadag coating on the CRT. To lessen horizontal streaking on a CRT one needs some HV capacitance. This could be either an early repairman's fix or a factory modification to use some 16DP4A's that Muntz or the repairman happened to have.

When one looks at the three alternate CRTs used with this chassis, one will see both the 19DP4A and 16RP4A carry an aquadag coating while the 16DP4A has no aquadag! So, this chassis could be a production line substitution where Muntz used a different CRT that they purchased for a few cents less than the cost of a 500mmF doorknob, or it could be just a serviceman's replacement CRT because he could not quickly locate a correct tube.

Jas.