Wow. Got the 10BP4…need a 12JP4 for The Doghouse! Also need a 17DKP4. Do these rarer tubes ever turn up in decent condition with any regularity? I’d also love to find a new or close to new 17 inch for the Predicta. I’d open the bank account for that one and the 12JP4!!!!!!

Yeah...but I think my wife would have the same reaction!

I've got a healthy 17" tube that will fit a predicta. The neck is about an inch longer so you'd have to mount the back hatch on standoffs. $150 local pickup or delivery to the ETF only (I don't want to box it).

I’m amazed it has FM. RCA wanted it killed, per Sarnoff’s orders.

Not really - Predicta compatible CRTs get snatched up quickly.

Are you sure you want a 12JP4? Remember it has no ion trap and will develop an ion burn. I'd suggest going with a 12QP4 to avoid this. 12LP4, 12KP4 or similar might be possible, but they have a different anode connector and are longer.
https://live.staticflickr.com/542/31...0c520182_z.jpg

Wow...same melt on mine. What a mess. Yes, I saw some threads regarding the 12QP4 substitution. Are the required changes fairly simple? FYI I have the Predicta tube wrong. The Princess is the 21" version so I will need to source a 21EAP4

Thanks Tom but I made an error. The Princess has a 21" screen so I need a 21EAP4. Unfortunately, I don't think electronic swap meets happen very often in my area so old and working CRTs are hard to come by. I have purchased 2 from the ETM but, right now, they don't have anything I need in stock.

Chris

I've never tried it, but it's my understanding the 12QP4 is a drop in substitute. Others will require you to cut off the anode connector and install a different type. The longer CRTs might not fit in the cabinet with the back on or require you to move the focus coil/yoke assembly further back.

The Princess, Debutante and Siesta have a 17" screen. Holiday, Pedestal and Tandem are 21"

If you need a 21", you are much, much better off with a 21FDP4 (or equivalent) than the original, flawed 21EAP4.

No, you're making an error now. The Princess is a 17" set. I know because I used to own one (I could also find some service info to quote if you don't believe me).

The only 21" table set is the wood cabinet Holiday model.

The only way a 21" Princess exists is if an owner swapped a Holiday or console headshell onto a princess (the top halves of the swivel collars and electrical connections are the same so the swap only requires 1 screw and 4 wire connectors be interacted with).
Philco never sold a 21" princess new.

So... what you are saying is, that a 21" Princess is a Philco Predicta Frankenstein!:D :scratch2:

I believe they made a 21" Princess model in Brazil. I don't think the 21" head will fit on a Princess cabinet. The CRT also has different specs.

Oh dear Lord what a mess I've made! I need to not post these things when I'm not fully engaged! This is what I bought. It does have a 21 inch 21EAP4

Philco Predicta TV Holiday In Mahogany G4242

I'm just looking for a straight substitute but I have heard the cathode emissions on these prematurely fail. So Bob, you're saying a 21FDP4 or equivalent would be the best way to go???

Never underestimate the power of kludge! :)
In the HS electronics lab, I bodged a 21 inch screen onto a 19 inch RCA tv using some old 2x4s I found laying around, it was literally an open chassis stuck on to the back of a frame holding the picture tube, but it worked! :D

LOL! :P

I'm starting to remember that crazy set now, it was a insane mishmash of what ever I found laying around, 21 inch BW, with a RCA chassis, it sat on my dresser, but I could control it from my bed, as I took the remote control servo motors from another dead set I found and tacked them to volume (on/off) brightness, tint & channel controls and had a long multi wire run to my bedside with all the buttons for it, it was truly a Rube Goldberg machine!

I used it until I was able to find my first color set.

ISTR someone on that predicta Facebook group you're part of sticking a debutante head onto a pedestal cabinet, so the reverse should be possible.
As for CRT compatibility the only difference is heater voltage. A series chassis doesn't even notice that, but a parallel heater chassis like the princess can be adjusted to compensate...In the princess and the similar chassis in the continental console all you have to do to compensate for a different heater voltage is swap the heater hot lead between the 2V tap and the 6V tap on the power transformer.

I've ran 17" headshells as test jigs for 21" chassis before so this can be done.