Philco 50-T702
 

I just got this TV off of CL for $15. This looks like it'll be my first TV. I haven't checked the 7JP4 CRT yet because my BK 467 doesn't list that tube. Anybody know how I can check it on my BK 467? I can make up and adapter using small alligator clips.

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Just wanted to say that was a great deal! It has tons of potential. The one negative with these are, I believe, the flyback transformers. They will run and then fade to dark. I had one, and even with a replacement part, still no luck, so I traded it. Hope you have luck with yours.

That is a great deal, the knobs for these are pretty hard to find though.

I don't think the B&K will test the CRT in any case, the only real way to test the 7JP4 is in a working set so you may have to get it working at least enough to see if it'll light.

Thanks. Yeah, I've been reading the Forums on this TV and we'll see.

I'll start the hunt for the knobs right away. I have friend who will test the CRT in a working TV.

I tested the tubes tonight. All tested in the green. 1 tube, a 7B5 had the glass envelope broken right at the base. 10 out of 17 tubes were Philco. The rest were GE, Raytheon, Hytron, National Union, and Westinghouse. Quite a selection that's for sure. Now I'll sit down and look over the Sams and get myself familiar with the chassis and do more web browsing on the Forums for other threads on this TV.

The underneath of the chassis looks like there are a caps replaced and that's it. Pretty much unmolested.

I have a friend who has a working TV that I can test the 7JP4 CRT. BTW, it is a Philco CRT. Anybody know how to get the metal sleeve off the neck of the CRT?

If you find the knobs and get it going if the high voltage gives you trouble I can send you a picture how I corrected the problem with a 7 inch Motorola Transformer and it works great.

Could you send it now? Thanks.

Why can't electrostatic CRTs be tested on a CRT tester like any other? Don't those testers just test emission? Dead would mean dead. Good might not mean good.

I've tested the 7 inch CRT tubes on my Beltron and most test good. The biggest problem I have seen is a tube that tests good may still be dim. I would guess phosphor degradation from ion burn. My 8 inch has a spectacular picture with no burns but I rarely use it. I run the chassis with a seven inch.
No need to remove the metal from the neck of the tube. To test them I just put the tube in a working chassis. I use a TS-4 for a everyday driver and it has its original CRT and after a couple of minutes it is bright and clear.
Love that Philco!!

Greetings: I just am completing restoration of this model set and its a fun one! Its a little cramped underneath but if you take your time you'll get it restored. I really suggest that you do your filter capacitors one section at a time (resist the temptation to just cut the leads and do all the sections at one fell-swoop). Its easy to omit something or make a mistake. Thats what happened to my set when a friend of the previous owner I acquired it from went through the capacitors. He made a couple mistakes which prevented the set from working, but correcting those errors resulted in a nice picture. Also you probably should not overlook the mica capacitors especially in the vertical and horizontal sections; I am seeing more and more of them getting bad and you'll see it in poor linearity. Pay special attention to the mica 100pF / 500 volt cap in the vertical amplifier!

Good luck and have fun! This is a cool set!

-George-

Others have already answered this correctly. If you have a working set with a 7" electrostatic CRT, that is the answer... But we don't all have that advantage.

I have a Sencore CR-70 that would test them. But as mentioned, even if they test good, they could have ion burn and be dim.

Good luck, these are fun to have and use.

I just noticed this on the 7JP4 CRT! It was missing a pin. I looked in the CRT connector and there it was. It looks like the solder connection failed. The connector came off the CRT pretty easily when I took out the CRT.

I'm thinking of soldering the pin back in place then using a bit of JB Weld to glue it down. I'll also touch up all the other pins on the CRT with my soldering iron.

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Well, I brought the voltage up to 50 then 10 more after that to 105 volts. All the tubes glowed ( couldn't see the CRT) and I got some sound. After some fine tuning I'm picking up a local FM station pretty good. The set at 105 volts draws 1.1 amps. The big problem is there is no video, nada!

I'm open to suggestions as where to look. I don't know if I'm getting any high voltage. How and where do I check that. I do have a Polaris HV meter.

Nothing got hot or any bad smells at all. I want to keep the run time down till I can recap this set. I'm pretty pleased so far, except the video of course.

Here's a video of it:

https://youtu.be/mOeAVBsoZVQ

Guys,

The heater ohms out good on the CRT.

There is no HV. I used my Polaris 40KV probe and no HV. I ohmed out the coil and it checked very good to the schematic values. I cleaned the pins on the 1B3GT and its socket too. I didn't see any glow from the 1b3GT but I think it might be real hard to see.

C96 looks like it had wept a little, so I think I'm going to order and replace all the caps in the HV section along with the HV OSC section too. Probably get the resistors too, won't hurt.

Next thing to do is get the CRT checked out on a working set. I'll contact my friend about that.

1950 Philco 7" sets are notorious for faulty HV oscillator design. They tend to bloom and fade after about twenty minutes. Not only is there no known cure, one dedicated restorer going to the trouble of replicating the oscillator coil resulted in a brand new coil that does exactly the same thing. Don't shoot the messenger.

Yep, I got one recapped and works well, for 15-20 minutes, then the high voltage fades until the pictures too dark to see. :sigh:

Well like any other vintage tv, recap the whole set including all the hv caps and then start from there because trying to run it with old caps is not a good idea should one decide to short and take out other components and make the job even harder in the long run.

Hi, There is a way to solve the HV issue in the Philco. You put in a solid state d.c. to d.c. converter. Now it is a bit pricey if buying new but look on the web to find used converters. Check out this site to see how 1 collector did this, http://www.myvintagetv.com/philco_hv.htm .All the best Tom

I have a spare one of those modules if you want it for 40.00 they also work great.

Yeah, I'm going to recap and recarb the HV section first, then the E-caps, then the rest. At least all the HV resistors too. First I have to see if the CRT is good or not.

Thanks for all the comments, I appreciate them.

:pity::pity:I had okayed my repairman to order one of those replacements (many years ago now) which wasn't cheap, and was so disappointed when I got a call that it didn't work. I believe I was able to return it. My Philco was in real nice shape and I hated to part with it, but having a non-working set in the collection doesn't cut it with me. Glad to hear there's been ways worked-out to fix the problem now. Now if I only still had that set!

I have said for YEARS..the best thing to to NOW..is to hide a small SS HV module somewhere in the cage (or under the chassis). They have some that will run fine at 6V. You just need to rectify and filter that for the module. One with say 5-7KV output should work fine for the HV.

Some questions on capacitors and what to order.

I have no problem with what to order for electrolytics.

For the "Bumble Bee" and tubular caps I should order the typical axial lead yellow film caps.

Then there are some caps that have the domino look and I think they are mica caps. There are only 5 of these in the TV. They range from 100pf to 10000pf (.01uf). I'm pretty sure some are mica but I think some might be paper caps.

Then there are some that look like little "hot dogs". These are all listed as mmf or pf in the parts list. There are 31 of them. If I need to replace them, what would I use? They range from 2.2pf to 1500pf.

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I'm including some pictures of them.
The schematic is listed in reply #14

Verticle and horizontal Micas would not hurt to change but I would wait on those caps until you get the hv up to see if the crt is bright, don't forget you are dealing with a troublesome 7jp4 crt unless tested on a working set to know for sure. And besides those Micas may be fine as you will see how good they are when you get it up and running.

I wouldn't change anything in the pf range unless there turns out to be a reason to do so.
The Hot Dogs are probably Ceramic, the Dominos Mica. The square caps of .001 or larger may be paper.

Anything pf or mmf is almost certainly Mica or Ceramic and probably in the i.f. strip where it will mess up the alignment if you replace them.

.01 is not a mica, those hot dog shaped and the others that look like a barrel with colors Are ceramic as well in your picks are usually good, do yourself a favor leave those caps alone even if the crt is good . You should recap the power supply first get it running then look for the hv if none then look for caps and or resistors that are related to hv, rectifier tube as well check or replace. If you have the schematic for that set then it will show what the domino looking caps are once you locate then on the set it will show mmf for the Micas .

If a specific set seems to bloom with the loss of hv then I'm sure when they were new they didn't have that problem, maybe because a cap that was not sized right for the hv section back in the day maybe failed after maybe 2 years and then after 50 years for sure it probably won't work so then why not find the problem or design defect and then that would be the end of that. Being both you guys seem to have the same problem and does look like a mistake was made in the design.

It's interesting that the drop off in High voltage does not seem to be entirely universal. Obviously there is a design flaw but also not every set produced displays the same result. My 50t-702 comes up nice and bright and yes, after 20-30 minutes I have to adjust the brightness. But after adjustment by it always is watchable and there is no discernible bloom. I've run mine between 90 minutes and two hours and never got so dark I'd have to shut it off! Interesting...

George

Maybe they didn't want to pay for a patent license to use a better design? Or just idiot managers telling the engineers to stop worrying and ship it? :thumbsdn:

Could be a manufacturing issue with the coils since some set fall flat and others only stumble a tad...

I'd make my own DC-DC converter, in your shoes. You just need a simple 555 osc. chip (and some R's and C's for it), a power FET, and a flyback from a junk BPC set. I built a 30KV plasma speaker that way with cheap parts and junk, and I'm sure I could de-tune it to produce 4-7KV.

I'm getting to know the chassis. I'm studying the schematics and parts layout. What I like to do is to mark each component with a little piece of masking tape the Item number from the parts list. I did all the Bumble Bee, paper, and square mica caps, the high voltage circuit resistors, the high wattage resistors, and high value resistors for now.

I enter the resistor and capacitor parts lists into Excel. Then I can sort them and it helps me come up with a replacement parts list that I need to order.

While doing that I came across a connection that wasn't soldered! The lead from the resistor just pulled up from the pin on the tube socket. While there was ample solder on the tube pin, the resistor was missed in that it never got a good solder joint.

I think I have a later run for this chassis. My Sams 140-7 shows the components, but I have more terminal strips and slightly different locations for some of the components. So far I've found all the components that I've been looking for. Yes, some of those pesky 1/2W carbon comp resistors can hide very well, very well indeed. Some of the paper caps shown in the Sams are Bumble Bee caps in mine.

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Yes anything is possible and maybe even the lack of enough b+ due to design although when new components were new but now so many decades later where all the components are tired and given Alittle more b+ things may be different since if these sets share these hv problems I'm sure everything has since been checked out and ok. Even resistors and coils that have resistance that is higher after so many years then that's ok if the set works but after a certain amount of time things happen, heating, but if this was multiplied several times over the whole chassis, who knows. Ah just thinking out of the box. :scratch2: :smoke:

After spending some time looking over this chassis I think everything is original. Nothing has been changed except for a few tubes. The picture tube is a Philco too.

Did you get the 7jp4 tested on another set yet ?

I contacted my friend and we'll get together next week and check it out. I think he mentioned he does have a replacement, though I can't recall directly. Untill then I'm just doing some homework and putzing. Won't order anything till after that.

Hey, just a shout out, I'm looking for the Philco Service manual for this TV. It's a Philco 50-T702.

The ETF website has the Sams for it. Here is a link to the page that includes the Philco sets Sams you can download:

http://www.earlytelevision.org/tv_sc...-p.html#philco

Dave

Dave,
Thanks for the info. I already DL that Sams.

I'm looking for the Philco Service Manual by Philco.

After spending some time looking over this chassis I think everything is original. Nothing has been changed except for a few tubes. The picture tube is a Philco too.