Hi All,

First time poster and a new Predicta Holiday owner. Before I get into questions, a little background on me. I'm a lifelong electronics tinkerer but have no formal education on the subject. I have a 'scope, variac, isolation transformer, signal gen and know how to use them. I have good soldering/remove/replace/repair skills. However, I have only a smattering of tube experience and no television experience at all. I am aware that the Predicta is a particularly difficult beast to work on. I'm not as worried about removing the PCB as I am figuring out why it isn't playing correctly.

The Predicta I got is in pretty good cosmetic condition. The plastic screen cover has scratches but nothing that can't be buffed out. Looking at the chassis, I see three replacement caps, done from the top and that's it. The power cord is broken and the power switch is broken, so hopefully it broke a long time ago and has been just sitting. The filament series resistor is un-bridged so I'm guessing that it has the 2V CRT tube. The CRT filament has continuity, less than an ohm. I can't see a number on the CRT, I'd have to take it out of the shroud. The flyback looks and smells ok.

Strategy-wise, the first thing to do seems to be to test the CRT, as if I need one of those I might as well wait to dig into this set as it appears it could take a long time to locate one. I don't have a CRT tester. I located a fellow Predicta owner who has one but his can only test 6.3V filament tubes. Can a separate 2VAC supply be used, such as a variac into a 6V filament transformer? Are there common CRT testers that have both 2 and 6v filament settings? Does anyone have one for sale?

Another way for a "proof of life" test might be to replace the caps in the power system, so as to not risk the flyback and CRT and then turn it on. Is this simply insane?

I have a ton of other questions, but for now I just need to test the CRT.

Thanks!

Jonathan

Welcome to the site!!!

CRTs are georgeous..... You will have fun testing them :)

I would just get a cheap bk 465 CRT tester, which can test all voltage crts and only bring $20-40 on eBay. You can usually look inside the housing by removing the rear cover. If you look down at an angle, the original Philco yellow tag will be on it and tell you the model and filament voltage of the CRT. Be careful soldering on these early pcbs. Too much heat and the foil traces will peel off. Check for any cold solder joints on the bottom of the board and make sure all traces are not broke anywhere. These are tricky sets that require patience, but having done a few myself, they're not that bad.

The few Predicta's I have worked have had a tag on the
chassis that says the picture tube is the 6.3v tube. But it may not have one. So you could start with the chassis and go from there.

...

Thanks for the replies!

I don't see any tag or markings on the tube itself. Attached to the shroud is a tag that reads: C 7100199 Part Number 319-2100. It is pasted over another sticker. I'm guessing it is a shroud number and has nothing to do with the tube.

Can the B&K 465 do the 2v and 6v filament? I know you said all voltages but I just want to be sure. I looked for a manual for it but couldn't turn one up. Since I see it recommended here and other places not to use these testers for rejuvenation, it seems that it can be done with the stuff most folks would have laying around, like in this link:

http://www.thevalvepage.com/teletech/crt_rej/crt_rej.htm

I'd use a 6.3VAC filament transformer and use a variac to get the voltage right and use a variable DC power supply for the 100V. Does this seem reasonable? Any tips or words of wisdom or links for rejuvenating?

Just how hard is it to find a replacement CRT for this thing? I could live with one with a too long neck if need be. Hopefully this one is workable but if not how far up the proverbial creek without a motivational device am I?

No one has mentioned the idea of replacing power supply caps to prevent major damage and see if the CRT lights up? Is this because only an idiot would do that? Or because there are just too many things that can prevent raster that it won't mean much as a CRT test?

Thanks for answering my noob questions, doubtless for the nth time. I am reading all the old posts and doing as much RTFM as I can.

Jonathan

No one has mentioned the idea of replacing power supply caps to prevent major damage and see if the CRT lights up?This TV does not have a power transformer, which is a major component that might be damaged by bad filter caps in the power supply. Instead, it uses a "series string" type power supply, where the tube filaments are connected in series.

This article has some restoration notes that you may find helpful:

http://antiqueradio.org/philc12.htm

The article discusses a Predicta in the pedestal cabinet, which uses the same chassis as the Holiday model.

Regards,

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

Phil, I have read your page with great interest before I posted. I have it bookmarked and will re-read. I printed out the PCB layout/xray view that you have their and mine seemed different. I'll look again, maybe I was looking ta it wrong.

Is the flyback vulnerable to damage without replacing some caps? I have located a friend with a tube tester so with any luck will be able to test the CRT this week.

Any thoughts on the rejuvenation plan outlined above?

Thanks!

Jonathan

EDIT: FOrgot to add the model number of the set, G4242-M

If it was me I'd just power the set up through a dim bulb tester or a Variac and see what you got, maybe jump the fusible resistor to prevent burning it out if there's a short, those things are hard to find nowadays.

There's a fairly good chance a set from 1959-60 will power up and give some sort of raster, it's probably been plugged in in the last couple years in any case because no matter what sellers tell you they just can't resist.

Steve, the power cord is borked right where it attaches to the back cover. I just checked and a molex connector has the right size female connector to arrach to the set. I realize this has a hot chassis and that sticking my fingers or tongue into the set with the back removed is likely to be an owie.

The power switch is also borked. It does conduct when pressed but it won't stay in. On top of that, I'm missing the knob, so there is another possible owie. I am quite tempted to jumper the switch and try it.

Is there really no or little chance of frying the flyback or CRT without a re-cap? I'm just trying to follow the physicians code and first do no harm, as I am utterly ignorant in the TV realm.

When ramping up the variac, how slow should I go? Should I ramp it in steps? What size fuse should I use in the variac, 1-2 amps?

Thanks!

Jonathan

The power switch is also borked. It does conduct when pressed but it won't stay in. That switch shouldn't "stay in". It's a "push on-push off" switch.

.

Well, it is acting as a momentary switch at the moment. Press and hold and it conducts but let go and it stops conducting.

Yes, the bk 465 is easy to use and can do both the 6.3, and 2v crts. A lot of these late 50s tvs have open sand coated Fusistors so check continuity on that also. The crts are hard to find unless you find a trashed Predicta. Be very careful testing it, because the socket in these crts use very brittle plastic and easy to bend tiny pins.

You mentioned about rejuvenating the CRT. I'd advise against that for now. Properly testing it is one thing at least to see what you've got. That tube is prone to being weak but it may still be good enough or usable. Unless you have a tester that has a clean function or something mild for rejuvenation don't be tempted. Even some manufacturers of testers warn about these tubes.

Thanks for the tester info. With any luck my friends will do the job. And the plan is to test before rejuvenating and I'll be asking more question here before I do so. However, assuming that it needs it, any guidelines for a mild treatment?

Thanks for all the help, folks.

Jonathan

If you variac it keep ambient light low and watch the plate of the H output tube...If it starts to glow then your fly is in danger.

I normally start the variac at 20-40V and step it up in 5-10V increments every 1-20 minutes....The newer the set/shorter it has been dormant the more aggressively I crank it up.

The CRT ID number will be 2 digits 2-3 letters (ending with a "P") followed by 4 (and possibly another letter)...For example "21EAP4". Most monochrome CRTs end in 'P4' and most color in 'P22'.

Mike, thanks much for the information. Very good to know to watch for the H tube plate and I'll ramp up real slow. First thing is to test the CRT. My buddy with the tester was on his way out of town and couldn't recall the model, so hopefully what he has will work. Once I have some test results I'll report here and see if rejuvenating is recommended.

If it passes I am torn between doing a total recap all at once or seeing if it works and replacing the caps one section at a time. I like the thought of doing it one section at a time, makes it easier to figure out if I screwed something up along the way. If I keep a sharp eye on the h tube plate, have an appropriate fuse inline and watch the current draw, how risky is it to try to light it up?

Also thanks for decoding the tube numbers. However, I'm guessing that not all 21" monochrome tubes will fit the plastic CRT cover. I haven't been able to find a list of Predicta subs. I could live with a tube that pokes out the back if need be.

Thanks!

Jonathan

On PCB sets save your self the trouble of tediously removing and remounting the board repeatedly, and just do the whole board in one go....Resistors that are out of tolerance should go, and maybe the couplates if you are in that camp.

Caps off the board are fine to change in any manner that works for you.

Oops, I see I somehow called you Mike, Tom. My apologies.

And duh, I wasn't thinking of the way the PCB is mounted. So yeah, gonna hafta do them all at once.

What is your take on the couplates?

Jonathan

Another question: Where is the CRT usually marked? I can't see any markings looking in through the back. Might removing the socket reveal them? Or do I have to take the tube out of the shroud?

Jonathan

The tube number is usually on a paper label stuck to the side of the funnel shaped part of the bulb. It is somewhat common for it to have fallen off and be laying loose inside the shroud.

As far as the couplates go, I would recommend replacing them while you have the PCB out. They are cheap enough to rebuild/replace, and saves all the work of pulling the board again. I believe Bob Andersen (bandersenTV) sells reproduction units already built.

Another common trouble spot on these sets are the tube sockets on the board. They are prone to cracking of the metal contacts, resulting in intermittent operation or outright failure. Check them carefully while the board is out and replace if needed.

I have always considered a rejuvination to be the absolute last resort with a CRT. Too many other things that can cause a dim dull picture.

Please resist temptation to do a rejuv. Often, this will destroy the tube.

I have always considered a rejuvination to be the absolute last resort with a CRT. Too many other things that can cause a dim dull picture.

Please resist temptation to do a rejuv. Often, this will destroy the tube.
Absolutely. A full and proper restoration first, then assess the tubes quality.

.

Oops, I see I somehow called you Mike, Tom. My apologies.

And duh, I wasn't thinking of the way the PCB is mounted. So yeah, gonna hafta do them all at once.

What is your take on the couplates?

Jonathan
I've personally never worked on a predicta (I'll explain later), but have worked on a few other period sets that use that style of couplate. Personally it depends on how much I'll use the set and how much money and effort are involved...I'll often just see if the couplates are good (have not had a dud yet), and leave them be if they work. If I was restoring a set for a client I'd probably change them just to lower chance of a call back. I probably would not be as phased about board removal on a predicta as some other restorers (who harp on it), but if it somehow really became a pain I'd just change the couplates to save me a headache.

The CRT ID is usually on a paper tag on the bell of the tube, but sometimes if the tube has a bakelite base the number will be there too.

I don't own a predicta because I feel they are the '57 chevy of vintage TVs....A common average performing set that people buy up and pay stupid money for despite the engineering, etc. being nothing special...Yeah they look cool, but there's a lot of other sets of the day that are cooler, rarer, and don't have a crowd of fanatics driving the cost of one skywards. If I find a cheap one (I do have a lead) or the Penthouse model (which is cool, especially the engineering, and rare enough to interest me) once I have cash, then I'll own one.

Tom, When I was a kid a saw a Predicta and somehow fell in love with it. I can see what you are saying though. Another plus is that the XYL loves the set too and wants it in the living room. They do go for stupid money, I paid $250 for mine and drove 4 hours each way to get it. At least I didn't have to pay shipping and risk having it smashed.

As to the couplates, I do plan to use the set weekly. I don't watch a whole lot of TV and in fact don't even own a TV at the moment. I guess I am leaning towards replacing the couplates. I'll do some more looking around at what it takes to make them and I heard that banderson of this forum sells them.

I have seen a thread about putting connectors on the PCB/wire connections but the poster didn't in the end. Seems like it might be a good idea. While this set won't see a ton of hours I do plan on using it for years to come so it might save time in the end. Thoughts?

I may have found a NOS 21AFP4 picture tube that may work with this set, either to replace the one in it or as a spare. I am still trying to determine how much has to be done to use this tube but considering the only way to get a "proper" tube is to buy another set and hope the tube is good. So unless it is too complex to do the required mods it seems like a good investment. I have started a separate thread on that topic.

Thanks so much for taking the time to answer what is doubtless painful noob questions. I do indeed appreciate it.

Jonathan

I have seen a thread about putting connectors on the PCB/wire connections but the poster didn't in the end.The following article has a section discussing the pros and cons of installing quick-disconnect connectors on the big PC board:

http://antiqueradio.org/PhilcoH3412LPredictaTelevision.htm

Scroll down to "Adding Quick Disconnects to the PC Board."

As explained in the article, I decided that the cons outweighed the pros. A thoroughly restored Predicta should not need frequent service that will require pulling that board out repeatedly.

Regarding the couplates, on any other TV I'd recommend leaving them alone and waiting to see how the recapped set behaves during a prolonged bench test. Having restored two Predictas, and recalling how much I disliked removing and reinstalling the big PC board, now I would lean toward replacing them preemptively. The article referenced above has sections on replacing couplates, but notice that it describes a different Predicta chassis than yours. The following article mentions couplate replacement in the pedestal/Holiday chassis:

http://antiqueradio.org/philc12.htm

As seen in the photo below, the couplate replacement can be simple -- a few parts wired onto a chip of perf board.

Regards,

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

http://antiqueradio.org/art/predicta19.jpg

Regards,

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

Phil, thanks for the link, great write up. I think I agree, the cons outweigh the pros concerning connectors. As to the couplates, that looks too easy to risk having to pull the board again.

And I forgot to reply earlier to Bruce and Wiscojim, I will NOT rejuvenate until the tube is tested and shows dead. And in that case I will seek advice on the best way of doing so.

Thanks!

Jonathan