Yet another Predicta Holiday restoration

[DaveWM]

another great job Bob. Now on to the Princess!

[bandersen]

Not so fast!

First off, I got a new tripod and better lighting on my workbench


Next, I wasn't really happy with having the electrolytics scattered around the chassis. So I found an old cap of the proper size, restuffed it and restored the original wiring.

I also added another 10 ohms to the filament dropped to compensate with the higher line voltages encountered today.


I also rebuilt the old dual diode assembly with modern diodes.


Then the "fun" process of installing the chassis. Remember I was just sent the chassis. The cabinet and CRT are from my set.


It played fine for a few minutes then the horizontal collapsed to a vertical line then disappeared altogether The sound is still good though.

I pulled the chassis back out and wiggled some wires. That seemed to fixed the problem at first, but after about 30 seconds it collapsed again. I pulled the chassis twice more with the same result.

So it seems to be an issue with a loose yoke connection or possibly over heating. I'm not so sure about heat though because once the problem occurs, letting the set cool down does not help.

[bandersen]

It was a pain to pull the set apart again, but I think I found the problem.

When the picture goes out, it collapses to a vertical line then quickly fades away. So I figure it must be an issue with the horizontal circuit.


Sure enough. A scope confirms that although the hor. oscillator is running just fine, there's no signal on the 12DQ6 HOT grid.

After a little poling around, I discovered that putting slight pressure on the K5 hor, network in just the right spot restores the raster. I figure there's a cracked PCB trace or bad solder joint under that network.

I wedged a bit of foam against the network and the sets has been running fine for a bout 30 minutes now. Next, I'll pull the board out and fix it properly.

[Phil Nelson]

Originally Posted by bandersen

I wedged a bit of foam against the network and the sets has been running fine

When I restored my Siesta, I found the plastic cap from a Bic pen wedged tightly between the main board and the chassis. At the time, I wondered whether it fell there by accident or it was purposely stuck there to "fix" an intermittent connection on the board. The TV worked fine after I redid the board, anyhow.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[bandersen]

It helps if you remember to actually solder the leads

[DaveWM]

I know this already but sometimes forget and then have to "re remember", but I am adding to my check list is a good magnifying glass and strong light, and just go over the pcb/wiring as part of my normal check out.

[bandersen]

I recently added some Xenon under cabinet "puck" lights. They get kinda hot but do kick out a lot of light and they're cheap

[NoPegs]

Based on his performance of the miracle of healing upon a severely stricken chassis, I believe Bob should be canonized henceforth as Saint Predictia IV.

[bandersen]

Well I don't know about all that I still have several Predictas to restored so we'll see.

I soldered up that open joint and reinstalled the board. The task was made easier because I happened to have another 9L37 chassis nearby for reference.


Viola! It works and has been running for 30 minutes without any more problems popping up

[ed857]

Bob,
Would you be interested in selling the round bezel + dial glass from your extra RCA 222 cabinet?

I sent you a email.

Thanks

[Notimetolooz]

[/QUOTE]

That's a nice bench setup, Bob.

Tim

[bandersen]

I recently received this photo from the owner showing the restored Predicta running in his office

[Down Under]

Looks great, but I definitely prefer the factory stand.

[Kevin Kuehn]

Hopefully he doesn't leave that test pattern on all the time.