Are there aluminized versions of the 16GP4 and 16AP4? I have two sets that use these tubes and both are dead. :tears: Might as well replace them with the aluminized versions...

I don't believe that the flash vaporization process they used to aluminize glass CRTs will work on a metal CRT envelope.

Are there aluminized versions of the 16GP4 and 16AP4?

You could get them in Tinted, Frosted, or Clear, but not aluminized.


Chuck

The frosted ones are good for cutting glare. They never offered aluminized versions. I think the metal bell made that impossible.
Bill Cahill

What do you mean by dead? Is the filament good and there is no emission? Or are there other faults?

Filaments are fine, zero emission though and I'm afraid to try rejuvenation.

Cook it at 8 volts for a while, it might come up.

Just out of curiosity, what exactly would cause a tube to "wake up" like that? What physical change would take place to make a tube work after just heating?

knocking off the corrosion and flashing/welding the getter from setting up:yes:
used my Sencore CR-161 it woke up a suposed dead 21ALP4...back over into the green

Just out of curiosity, what exactly would cause a tube to "wake up" like that? What physical change would take place to make a tube work after just heating?

I suspect that the major effect is to evaporate contamination that has built up on the surface of the cathode after sitting cold in a not perfect vacuum.

Some other possibilities:
Bring fresh emission sites to the surface of the barium carbonate cathode coating.
Release "co-activators" from the nickel cathode sleeve into the barium carbonate cathode coating.

See "Process for Activation of Cathodes" in this link near the bottom of the page:

http://www.transene.com/cathode.html

Step 1 & 2 occur during initial processing of the CRT, on the vacuum pumping station, I believe that step 3 & 4 are repeated during the 8 Volt "hot shot" and subsequent operation of the cathode at normal (or slightly elevated) temperatures.

Try it, it usually works for me, and if the "tube is dead" you don't have much to loose.

jr

My RCA 16AP4 had absolutely zero emission. When I collected the set, it had a brightener on the tube. The brightener simply runs the filament at a higher voltage and the extra power is to heat the cathode to bring up emission.

The earlier CRTs like the 16AP4 have fairly substantial cathodes and so I was not worried about rejuvenation. Running the cathode at 8 volts for hours made no change.

The rejuvenation process produces a controlled electrical arc between the grid and cathode to presumably strip the non-emissive and contaminated layer of oxide from the cathode. By a careful use of rejuvenation (one shot) followed by a clean, I brought the tube back up to good emission. It has been consistently good for about six months now and I no longer use or need the brighterner! Do not expect the tube to be as bright as a '60's set but at least now produces a good clean and sharply focussed image on the screen with adequate contrast. I posted some images earlier:

Note the set, an RCA 9TC275 has only 11kV to 12kV Hi-Voltage for the CRT but it is enough to provide a good watchable picture in the living room in the evening.

Remember, over doing the rejuvenation will be lethal. I have detroyed a trinitron tube with rejuvenation: one rejuv shot brought up emission and a foolish second try killed it permanently. I do not think one rejuvenation will hurt the 16AP4. And besides, what else have you to lose?

Looked at the pictures from my earlier thread.
http://videokarma.org/showthread.php?t=251172

I left the tube for six months dormant and when I fired it up again it still worked but emission was down slightly. I simply did a "clean" and it brought the emission up again. I won't be inclined to touch again.

As I mentioned earlier, I believe the tube has some gas (slight whitening of the getter) but it still works okay with no blue purple luminescence in the tube. The evacuation nipple is metal and I would guess that there is a very very slow leak...

One recommendation on rejuvenation. Beg, borrow or buy the most recent Rejuvenator you can find. Something like a Sencore CR31A (Supermack) or CR70, BK 467 or newer, etc. They have much safer and effective rejuvenation functions than the older units out there. The older units simply charged a large cap and you let 'er rip with the 'rejuvenate' button with next to no control.

However - I personally do like to keep one of these old units (a BK 445) in my car for spot testing a CRT when visiting potential candidates for my hobby. The 440/445 is small, cheap and great for a quick check of emissions, shorts, etc. I also use it to wake up CRT's (running the filaments at normal voltage) for periods of time - or in some cases running the filaments of suspect tubes at slightly higher voltages. Saves wear/tear on the more expensive testers for this function.

My 2 cents!

Mark

One recommendation on rejuvenation. Beg, borrow or buy the most recent Rejuvenator you can find. Something like a Sencore CR31A (Supermack) or CR70, BK 467 or newer, etc. They have much safer and effective rejuvenation functions than the older units out there. The older units simply charged a large cap and you let 'er rip with the 'rejuvenate' button with next to no control.

Mark

This a very good point. I fully agree. I used a BK 467 and would have been hesitant to use anything older.

The 19AP4C is supposed to be aluminized, and that's the only metal CRT
that I know of. I did pose that question to an older gent at Clinton years back. He told me that the phosphor required a protective laquer
coating to protect it during the aluminization process. But, due to the tight corner created by the bonded faceplate, the laquer was difficult to remove entirely during final evacuation. I did want him to aluminize a 16GP4 for me,
and he said he would give it his best shot. I would only get charged if it
was successful. But, that was right when Clinton went to new ownership,
and the new owners said no to all metal tubes.