Aluminized 19AP4?
For what it is worth, my old GE tube manual shows the following for the 19AP4:
19AP4; clear glass, single magnet ion trap.
19AP4A; gray glass, single magnet ion trap.
19AP4B; gray frosted glass, single magnet ion trap.
19AP4C; gray glass, aluminized, single magnet ion trap.
19AP4D; clear frosted glass, single magnet ion trap.
I bet that some were also rebuilt with straight guns, as well.

Poor/complicated layout?
To me, it really looks like a "factory kludge"... The chassis still has the punch outs for the (5) 25Z6 rectifier tubes used in the 10 inch models plus other unused punch outs. :scratch2:

jr

I've never seen an aluminzed one either, but the Tung Sol data sheet does say
19AP4C - Grey Filter Faceplate Aluminized Screen

http://frank.pocnet.net/sheets/127/1/19AP4.pdf

For what it's worth, I had a necked 24AP4A that had an aluminized screen, so at least some metal cone tubes were being aluminized either by the manufacturers or the rebuilders.

Aluminized 24AP4?
For what it is worth, my old GE tube manual shows the following for the 24AP4:
24AP4; gray glass, single magnet ion trap.
24AP4A; gray glass, aluminized, single magnet ion trap.

I doubt that rebuilders normally aluminized or even redeposited screens, anybody know of one that did? :scratch2:

jr

RACS in France was still aluminumizing and phosphoring until they closed. Hawkeye was doing it in the early days when Scotty's father was still running the company. After the move to the final location that Scotty ran, they no longer did either process. At the new location all they did was re-gun the tube.

Short of breaking one open and checking how would you know if a metal cone tube was Aluminized?

You can tell on a glass tube because you can see it from the back side, no such luck on a metal tube.

For the moment, I'm going to assume that the last guy who had this set knew something about the components that I don't, and replaced some stuff or something that required the caps and resistors that don't show up in the schematic. I mean, you usually don't throw what looks like expensive high-wattage resistors into a set without a good reason, right?

You're right though, the wiring is kind of like a rat's nest, but I've dealt with a lot worse. My plan at the moment is just to finish up recapping, and see where we're at. After I got everything hooked up that wasn't, and got a lot of the caps in, I pulled the 5U4 and bench tested the chassis to see if the transformer was good. Ran nice and cool and all the tubes lit, so that's a good sign.

With an image on the screen, you can tell by looking down the neck of the tube. On tubes that weren't aluminized, you will be able to see the screen image reflecting off the gun assembly. At just the right angle, you can usually see all the way to the screen.

Clinton electronics did. Each of their rebuilds went through the oven 3 times.
They were North of Rockford, IL.

The early chassis, you're referring to, used in the 10" model with the 25Z6's was a totally different layout.
This chassis was used in the slightly newer models, with CRT's from 10" to 19", some with AM-FM radios. The front right corner, looking from the rear, had all kinds of knockouts for the radio IF transformers and tubes. It was cheaper to use the the same tooling, than to make up new.

Thanks for the correction, I have not seen a 25Z6 powered set in years and there is indeed a strong "family resemblance" , especially with the pattern of holes approximately in the area where the 25Z6s would have been.

jr

Think about it logically...Back in the days of monochrome sets being more common than color 'bright spot' suppression on power off was often lacking, and customers often listened to their sets after deflection failure resulting in horizontal line burns (not to mention possible ion burns). All of that was common back then, and not all of that is easy to check for when accepting rebuilds, but it will make the finished product unsellable (especially if they handle enough of the CRT type that clients are not necessarily getting 'their' CRT back). It is relatively cheap to rephosphor monochrome CRTs (compared to color CRTs). So something that would fix those issues would be a money maker. Once color CRTs that are mostly not able to be economically rephosphored became the most common rebuild jobs the monochrome rephosphoring stations likely became a waste of space.

Makes sense! The only rebuilder operations that I remember seeing were doing mostly color CRTs at the time and had no phosphor deposition facilities. They could however, re-bond the safety shield on color CRTs, (another time consuming, tricky process).

jr

It goes to the yoke socket for the picture tube. This is Sams 126-5, same as yours.

I have to say that the quality of this set compared to others I've worked on of this era isn't anything to write home about. Cheap parts, crappy sloppy wiring.

What pin #? ... Perhaps we can reverse engineer the resistor connections and figure out what they were trying to accomplish. :scratch2:

jr