My Attempt at Predicta Restoration

[PredictaNoob]

So, I went with a compromise. I moved the electrolytic replacements for E3 off of the MB.


But instead of trying to re-stuff that slender can, I mounted them to a bus bar.



I'll give this a try, and if I decide I just can't live with it, I'll order some radials and restuff the can.
I am re-stuffing the larger 4-stage E1 can.

[PredictaNoob]

I did score a set of the decorative arms and a new replacement cord.


The arms have two small posts intended to lock them in place on the base.



So, now I'll have to drill a pair of small notched holes on the CRT mounting base.

[DaveWM]

Just a thought, its your set, but adding arms to a set that did not have them originally may make it less collectable.

[PredictaNoob]

Originally Posted by DaveWM

Just a thought, its your set, but adding arms to a set that did not have them originally may make it less collectable.

Yes, that occurred to me as well. Two factors swayed my decision: 1) I found several precedence of the same model with these arms, leading me to to believe you could purchase this option. 2) Greatly enhances the WAF

I'm already completely unfaithful to the paint and grille cloth, and since I've no intention of parting with it for the foreseeable future, I'm OK with it.

[PredictaNoob]

Eh, I've been thinking about what you said about the arms for most of the evening. I believe I'll hold off on the drilling. Maybe I'll hang onto the arms for my next Predicta.

I was able the replace the antenna using an original mount (with only one remaining antenna section) and a replacement antenna of similar size. I really had to man-handle the mount to get it open so I could remove the ball and single section, and replace it with the donor. It took a bit of sanding and soft scrub to remove the chrome (so the gold plating would 'stick'). The first session of gold plating turned out about 75%. Once we get back home later in the week I'll attack it again and see if I can get more plating to adhere. Its looking really good so far.

Hopefully the resistors will be here too...

[DaveWM]

nice with the antenna, most I have seen (including mine) are pretty rusty around teh base, but the rest of my antenna is good.

Yes holding on to the arms for the next one is a good idea, as most have very rusty arms, and lots of pitting.

[PredictaNoob]

Granted this has absolutely nothing to do with this thread (or the entire forum, for that matter) but this is why I am on pause with the Predicta project:


View from our gasthaus window, Gasthaus zum Fischerwirt. We're here to see the Oberammergau Passionspiele (Passion Play) that's been acted out here more or less regularly since 1633. The play starts in 4 hours, so I'd better get going!

[PredictaNoob]

I finished replacing all remaining components tonight. Here's a photo of the finished main board:

[bandersen]

Nice job I notice you left the old couplates in. I've heard some guys rebuild them. I just picked up a Predicta and it's running fine with the originals. I wonder how prone they are to failure

[PredictaNoob]

Originally Posted by bandersen

Nice job I notice you left the old couplates in. I've heard some guys rebuild them. I just picked up a Predicta and it's running fine with the originals. I wonder how prone they are to failure

I bought a complete set of good used ones from Ross Marshall, just in case.

[DaveWM]

1st turn the brightness all the way down, and check the 220k resistor that goes to the brightness grid on the CRT to make sure it is not open.

Predictas are known for bad tube sockets, if the vert tube is lighting up, then try it while wiggling the tube around.

Check the primary of the vert out transformer.

check the pin resistance of the 6DR7 tube to the sams values

425 to the 275v
2.1 meg to ground
2.1 meg to ground
.1 to ground
0 to ground
3.5 meg to the 275v will vary depend on control setting
68k to ground
50k to ground will vary depne on control setting
450 to ground will vary depending on setting
1000 to ground



Check voltages at the tube pins, this is where a socket extender comes in handy.

[Phil Nelson]

Originally Posted by bandersen

I wonder how prone they are to failure

I think the answer is "sort of." My understanding is that the capacitors inside are paper. I replaced one (K4) preemptively on my Predicta, having been told it was a troublemaker. The others are working fine, 10-odd years later.

Some folks replace all of 'em, some folks replace none. I guess I would consider [A] how well your set's working now, [B] whether you plan to do other work requiring removal of the big PC board, and [C] how much you hate the idea of possibly removing the board only to replace a failed couplate.

How's that for not really answering your question

Phil

[PredictaNoob]

So, I plugged it in, said a prayer, turned it on, held my breath, and it slowly started coming to life....
sort of.

All I got was a single white horizontal line across the screen. And after about 30 seconds or so, I saw and heard a static discharge coming from the cheesy crimp connector on the HV wire, arcing to the chassis. It scared the crap out of me, so I turned it off.
Since its a vertical field problem, I'm thinking I've got a bad solder joint. Not sure what to do about that HV wire connector though...

[andy]

...

[Phil Nelson]

If they're all ceramic, maybe I should change my thinking. How did you check the resistors before digging them out? (Asked another way, would it have been less work to make a new one?)

Phil