First Time Predicta Owner

[.Mark Steven]

I just purchased my 1st Predicta. The Debutante model with the 11L43 chassis. It was just down the road, so I couldn't pass it up. I'm excited to have a project to play with although I fully understand these tvs aren't recommended for a rookie. I want to give it a go.
Got it home and immediately removed the chassis. Hoping the set wasn't tampered with too much, the first thing that caught my eye was the modification that a previous owner had done to it. See photo below. It's supposedly been in storage for 20 years and the replacement electrolytics seem to be larger than currently available.
Let me know your thoughts on this beast, and thanks in advance for any help you provide as I start to dig into this set. The pics may be difficult to see what was done. Basically it looks like he snipped one end of the ceramic resistor added his electrolytics and another ceramic that runs down to ground. Ugh. I don't like bodged repairs.


Can anyone tell me what this modification is and what would make someone update the electrolytics like this. I'm still familiarize myself with the boards, but it appears only the largest value electrolytic caps were updated, but the cans haven't been touched. Except for repacing C1 with a 200v 470 electrolytic. 20241026_132238-1.jpg

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20241027_200624-1.jpgThank you.

[Electronic M]

Besides those ceramic resistors (tracing out where they go on the schematic is necessary for full understand) everything else looks like standard electrolytic replacement... Maybe not the cleanest workmanship, but not necessarily a problem either.

For a long time nobody made FP twist lock style electrolytics so the only option was modern individual caps mounted like that, to an add on terminal strip, or to the circuit board (there's actually some good empty spots on the circuit boards for some of the lytics.

There is a company that makes reproduction can lytics but they're several times more expensive than replacing with individual modern lytics so few are OCD enough to spend the cash.

These sets aren't terrible to work on if you can figure out access. Most caps you can get at through chassis holes under the PCB, if that isn't good enough you can unscrew a couple of the transformers and a couple of the wires with the least slack and hinge the board up to improve the poor access.

All the paper dielectric caps (including the ones hiding in plastic shells) need to go, the couplates probably need to be replaced (I've gotten away with keeping them in most of my predictas), change off tolerance resistors, and keep in mind the circuit board mounted miniature tube sockets suck ....they will go open with too many in and out cycles so unless you want to change them try to only have any tube out once for a test.

[Alex KL-1]

Welcome aboard!

Good luck with you restoration!

[zeno]

Watch some of Bandersons U-tubes. He has probably restored more
of these than anyone. The go to man.

Zeno

[.Mark Steven]

Thanks for the input guys. I've almost completed my mouser order for all new caps,resistors, electrolytics and the diodes. In the process, I'm familiarizing myself with the board and schematics. Other than those electrlytics, and that weird mod, I don't see anything bad or touched. I've ohmed out a few things and so far they seem ok. Using the schematics, I went back to that mod and can see what the guy did, but I don't understand why he tapped into the circuit where he did. I'm assuming he was replacing the 200uf cap from C2-B, but it's definately not connected to the same line in the circuit. I can't believe that's an appropriate place to replace the electrolytic. I would think that not having C2-B where it's supposed to be would screw up everything else after it (but then what do I know). Just seems really odd and I have to wonder if/how the set worked. I don't expect anyone to dig out the schematics, but if someones familiar enough with the circuits maybe you can take a look. The photo is a diagram that I believe shows what he did.
The other reason for modding this might be to fix a problem and isn't related to the C2-B replacement. I haven't pulled the board yet as I'll wait for new components, so I'm not able to do a better trace of the wiring. I'm sure many things will be easier and clearer after pulling the board. It just bugs me that I don't see why he stuck that wirewound resistor and 2 caps where he did.
Just to be clear. The 4100 7W resistor is the original on board component and the 1k wirewound and the 2 caps are added components. Maybe I should dim bulb this thing before sending my mouser order off and see what happens.?.

Thanks for all the advice. I'v watched many many Predicta rebuild videos and learned a lot in a short time. One piece of advice from Jordon Pier that I didn't follow was to not use a Predicta as your first rebuild. LOL! I like a challange.

[Alex KL-1]

Strange, this network are feeding something, or the previous tech cut it?
Anyway, the caps are in series, to cope with the voltage here. But, they need a bleeder resistor (220k in // with each one).
Really better to wait schema and parts, for subbing at least the critical ones, before more testings.

[.Mark Steven]

Originally Posted by Alex KL-1

Strange, this network are feeding something, or the previous tech cut it?
Anyway, the caps are in series, to cope with the voltage here. But, they need a bleeder resistor (220k in // with each one).
Really better to wait schema and parts, for subbing at least the critical ones, before more testings.

Thanks Alex. It seems strange to me too. Yeah, I've found the SAMs for similar model and am familiarizing myself with that. The boards are nearly identical, but the C and R number they used is different. Not a big deal. I'd like to find a Philco Service Manual too sometime. The more info the better.
It's starting to make more sense as I trace things around the SAMs. My parts order is complete so that's been done with Mouser. I'm wondering if the modification was done to make up for not replacing the 4 sections in the big cap can. Just seems like a goofy mod to me but we'll see.
Thanks again!

[zeno]

In the early days SAMS usually had different reference ##'s than OEM.
( R, C, D, V etc) That ended in the 70's. OEM manuals are matching.
But all manuals are subject to the librarian. lost suplements etc.

Zeno
LFOD !

[.Mark Steven]

Needing advice from the experts. I've replaced all caps and resisters on the main board and just waiting on new power resisters to replace the old sand resister that looked ok but obviously toast.
I've checked the power transformer and fly back. Ohms seem reasonable but the vert transformer is funky. SAMS shows 425 ohms between red and blue and 2.5 between the top 2 secondary lines. I'm getting 264 and 3.8 ohms. All board connections are in place. Would that throw off my readings or is my transformer ill? Thankyou for any advice!
Edit- Just pulled the red line off the board and still just 264 ohms.

[.Mark Steven]

Well, as luck would have it, it looks like I have a bad power transformer in my Predicta. I replaced the fusistor since it was bad and replaced with new wire wound resisters. Powered applied and the resisters popped and smoked. Disconnected all transformer leads and things don't look
good. 77v on both yellows, 0v on red and the white with black tracers.
Are there any options to replace this thing short of trying to find an old chassis. Does anyone have a working transformer? I'm out of ideas on how to proceed.
Thanks ��

[Electronic M]

If you have sufficient enginuity and a stock of used pull transformers you can usually make something work electrically if not mechanically. I've done that in some tube audio gear before.

For a perfect replacement look for another rough 17" predicta with a bad CRT as a parts set.