21fbp22 $59 Bin

[Eric H]

Unknown condition.

http://cgi.ebay.com/Round-Color-Pict...QQcmdZViewItem

[Pete Deksnis]

Interesting. Built by RCA late in 1961 for use by Zenith in their first color sets?

[reeferman]

Dunno. Would the EIA 274 indicate manufacturer or what the product number is? I think it is of RCA mfg cause a Zenith would have the Zenith script with the Rauland name on the tube someplace

[Eric H]

The 274 means RCA, I just read that here:

http://antiqueradios.com/forums/viewtopic.php?t=76947

The post dated 17 Oct 2007 18:43

[ChrisW6ATV]

Seems like a good deal even for a rebuild dud, but the local pickup limits it.

[freakaftr8]

How the heck do you ohm test a CRT?

[jpdylon]

Even if you do get heater continuity, you still don't know if one of the heaters is out, nor gun emission, leakage, gas, shorts, etc.

Its a crap shoot.

[freakaftr8]

My CRT works, but how do you ohm test it?

[jpdylon]

I think the only ohm test you could perform on it would be to ohm out the heater filament. Again, this is really only to tell if a heater would light up, and doesn't tell if all heaters are good nor emission.

The CRT tester is really the only way to test if the CRT is good --and of course seeing if it will hold a good grayscale, and color picture without looking chalky, or defocusing even though voltages are normal.

The tester puts a small amount of current between the gun elements. The amount of current measured in micro amperes is the gun's emission --or at least a way to measure it. More sophisticated testers will detect grid leakage or gassy tubes. How they do that exactly varies by manufacturer --and quite frankly I don't know

[freakaftr8]

got it... Thanks! Just hoping to see my CRT tester soon!! The dude on ebay accidently sent it off to Japan!

[jpdylon]

yikes. If you don't see it in the next 30 days, file a claim with ebay. The seller might have stiffed you.

[freakaftr8]

Yeah, he actually sent me a cheap-o- tube tester instead, he said he was sorry, and wants me to return it asap. Im thinking maybe I should hold onto it until I get the CRT teter...

[jpdylon]

ayup.

[Chad Hauris]

You really cannot rely on an ohm test even to see if the filament will light...have seen some CRT's that had micro-cracks in the glass somewhere and went gassy and even though there is filament continuity, there is air in the tube and it won't light.
If you can put 6.3 volts to the filaments with some alligator clips and the tube lights at least it is likely still under vacuum.