Hello all.

I recently got a couple Philco Predicta Holiday's (one in fair shape, one in parts only condition). Both have rebuilt 6.3 volt 21FDP4 CRTs.

I'm planning on bringing the one I'm restoring up on the variac soon, just to see if I can get the CRT to show signs of life. If I can, it'll help me justify the electronic restoration time that will surely be involved. Both CRTs register on my Sencore Big Mack, not perfect, but they do show signs of usability.

The main concern at the moment is a wire which connects from pin 7 on the CRT to the chassis. The wire is separate from the others, and not part of the two main connectors. Since both sets came with the wire disconnected, I don't know where it's supposed to connect on the chassis side. Anyone know?

Is there anything else I should be aware of before bringing up the voltage? All tubes check out fine, the filament resistor shorting jumper (added when the set was modified for 6.3v CRTs) has been removed as per some recommendations, and I'll double check that there are no shorted filter capacitors. I plan on replacing all the paper and electrolytic capacitors, but I'd like to see if I can get the CRT to at least glow before I put in that kind of time. Let me know if that is a bad idea.

I'm aware that the chassis is tied directly to one side of the AC line, so I'm going to make sure that's the neutral while I'm working on it, always testing before touching.

I am looking for a copy of the schematics as well, if anyone can help me out there. I can no longer read the magenta colored stamped number on the chassis which listed the number, and I'm missing the back, so is there any other way to identify the chassis model?

Am I missing anything? I usually bring up the voltage in increments of 10v every 10 minutes. Should that method be modified for this set?

Any other Predicta related notes would be very helpful.

Thanks!

I am not a big fan of bringing up TV's that slowly with the HOT in circuit. I cant prove it, but I don't like the idea of med low voltages there, just in case the horz osc fails to work and then the HOT draws too much current (granted its also going to be lower voltage so it may not matter).

I generally pull the HOT out of the circuit and then do a slow start, while monitoring the the AC currrent and voltage, and the B+ current and voltage (would not work of course with string series filaments).

Before starting any of this I will check the B+ resistance to see if there is any shorts, esp in the filter caps. I use a reg old analog VOM and just hook up at the input of the filter cap, should see a somewhat low reading to start then a swing back to around 10k-15k as the cap charges. If it passes this then proceed with the slow monitored power up.

You could be extra careful and just disconnect the doubler (since its a line set I assume it has to use a doubler power supply) caps and check them as well as the filter cap. Might save the choke if the filter cap is shorted, but a careful watch of the B+ current and well as checking for (caps and choke) will do that as well. I have a variac that also has a isolation trans which take care of the hot chassis. Be ware, the only real safe way to make sure a chassis is not hot is to use a poloarized plug, with a polorized chassis plug, and then make sure the not side goes to the switch and the return from the switch is NOT to the chassis. I have seen some AA5 radios that just had ther switch connected to the to the chassis, so the chassis was hot either when the switch was on or of depending on how it was plugged in. The saftey was from the interlocks and plastic case allowing no metal to come into contact with the chassis.

The yellow lead from the CRT socket connects to a terminal lug on the PC board. It is on the edge of the PC panel near the video amp, below the maroon Erie Pac.

The correct lug will have nothing else connected to it. Important; dress the lead away from the yoke and HV wires to avoid sync jitter and horizontal foldover. Don

Thanks for the advice. I'll take my time and check everything before attempting power up.

I noticed that the yellow lead is routed through the case in such a way to keep it as far from the other wires as possible, so I'll be sure to keep it that way. I noticed that pin on the PCB with no other wires connected to it, but I thought it might have been for the speaker (don't know where that connects either, but that's not a concern at the moment).

I found a copy of the Sams Photofact, so I finally know what I'm looking at.

Another quick question:
I know the 2.35v 21EAP4 CRTs were very unreliable, but how does the 6.3v 21FDP4 compare? I assume they're probably more reliable, but how much more likely are they to work today?

The speaker connects to L-7 and L-8. They are on the same board edge below the video connection close to the 9BR7 tube. They should be a black and a green wire if they are still there.

The 21FDP4 will work OK in place of the 21EAP4. Heater current is the same, 600 ma. The voltage will be fine. The 2.35 vs the 6.3 will even out over the string with no problem. Don't waste any time trying to recover the four volts. The set is designed to work over much greater variations.

The CRT Screen grid connection may need to be moved, depending on how the socket is wired. If so, the best way is to carefully drill out the socket rivets and move the connection from pin 2 to pin 6. If it is already on pin 6, it will work. Reassemble the socket using small nuts and screws.

Overall length is about 1/4 inch longer. There is normally enough clearance in the CRT housing if the tube is mounted correctly.

In short, with attention to details it will be fine. Don

Thanks for the reply. I have one intact speaker out of the two sets I have, but it's a different size than the one that was in the cabinet I'm restoring, so that's going to be addressed later on. Good to know where it connects.

As for the CRT, I should have clarified:
The 21FDP4s I have were installed years ago, either from very good repair shops or by the factory by the looks of the installations. The wiring difference has already been implemented, and the series filament resistor has been bypassed in that area (a modification which I have removed).

I was inquiring more as to the reliability/lifespan of the 21FDP4 compared to the 21EAP4 CRTs. I'm assuming they're more reliable than the 21EAP4, since they were replaced for some reason, but how much so, and should I expect problems with them down the line?