HI everyone Im new to the forum. I just picked up a Philco Predicta Tandem last night. The story behind the Tv is the person who sold the TV to the woman I bought it from said the TV worked. She brought it to their house and plugged it in but the set wouldnt come on, she swore up and down that it worked, but they never could get it to work. When I got there last night she thought she would turn it on when I pulled in so it would be warm and I could see what it does..... SO hopefully she didnt totally cook it. When I got it home last night and hooked up my B & K 465 and proceeded to test my Picture tube. At first the tube tested as gassy, but after letting it warm up a about 5 min the tube passes with flying colors!! I took the chassis out and turned it on with the tube hooked up and I got no picture or sound but all the tubes did glow. I proceeded to check the fusistor and the filament dropping resistors for an open. My meter says the second terminal of the filament dropping resistor is open, and I got no continuity through the fusistor. From everything Ive read this set was built with the cheapest electronics they could find. So Im assuming I will have to replace all the caps and resistors at the very least. But Id really like to try and get the set to fire up for 2 reasons one is just to see it work, and the other is to shut my Mother and Fiance up who keep saying its junk and it will never work I should just throw it out.... So Id really like to get it to come on. What are, good replacements for the fusistor and the filament dropping resistor? SO far the only cap I see that has leaked a little is C1 on the Sams 441 photofact sheet I found.
>What are, good replacements for the fusistor
See pic...
> but all the tubes did glow.
>My meter says the second terminal of the filament dropping resistor is open
If the resistor was open all of your tubes wouldn't light. Did the dial lamps in the tuner come on??
>I got no continuity through the fusistor.
Probably a good thing. This will kill any hv being produce by the power supply. I would think that it's a bad idea to just replace the fusistor and hope for the best. There are a number of large value cap in the p/s that if they are electrically leaky will take out the fusistor and diodes just for starters.
Would replace the electrolytic caps before trying to power it up. Without that you are asking for a poke in the eye [Image: http://philcoradio.com/phorum/images/smi...on_eek.gif]
> built with the cheapest electronics they could find.
I guess you've never heard of Muntz??
>So I'm assuming I will have to replace all the caps and resistors at the very least
I would check the resistors for reading in tolerance replace bad ones. Disk caps would leave alone. Horz and vert intergraters more than likely with need a rebuild.
GL
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
>If the resistor was open, the tubes would still glow.
If you mean the Fusistor yes this is true.
If you mean R-80 section B if you unplug the tuner to measure that section it could measure open and still operate the heaters as the tuner heater is in parallel with that section. So the current would flow thru the heater rather than the resistor.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
First I want to say that I am new to fixing an old tv, for the most part I can read a schematic, I know hot to solder, and Im generally good at trouble shooting. I'm an electrician by trade so I have a general knowledge of electricity and what caps and resistors do and are used for. But by no means am I a tv repair man. So please be patient with me.
Last night when I tried the set all the tubes and the dial light lit right up. Tonight I went to try and test for power by the tuner, and when I plugged it in nothing lit. Not the tuner dial or the filaments. I grabbed my meter and saw I have power going though the switch. Then I metered from one leg of the 120v feed to the fusistor R78 and got 80v on one side and 118 on the other. Then I tested the resistor R80 and with one lead of the tester on the power feed and the other on each of the terminals I got 118v so it doesn't seem to be creating resistance. Then I unplugged the set from the wall and hooked up one lead of my meter to where the hot wire attaches to r80 then metered each terminal and still got no reading on the second one, which looks like the 8 ohm terminal. I also did the same test with what I think is R79 and it read 118v on both sides also. Its hard to tell from the picture because its kind of light, but the part I tested is a thick round disc it almost looks like a black mentos with a lead coming out of each side.
The other thing is what is the best way to clean the main board. I tried to follow the diagram and just check each resistor on the main board one at a time, and a few of them were open. Im wondering if its just crud on the board. The whole thing is dusty and sticky so Im wondering if its keeping me from making a good connection?
Also does your average DVOM have enough power to get a cap to charge? I set the meter to Diode test and I tried to see if C1 would charge and it read open.
I don't want to just go nuts and replace every single part of this set to make it work, Im trying to see what is actually going on. Or am I looking at this the wrong way and I should just replace everything? When you read about these Tv's on the internet it makes them sound like theyre very unreliable. But things usually get blown out of proportion on the internet, if they were all lemons I think theyd all be in a landfill by now and we would have nothing to restore....
Also is it worth leaving the wire wrapped connections intact, but cutting the wires in the middle and putting a male and female spade connector on them so you can service the board easier down the road? Or will they pick up interference and just cause trouble?
(This post was last modified: 02-28-2018, 06:24 AM by apERNA1985.)
>But by no means am I a tv repair man
That make two of us. I have fixed couple of dozen over the yrs.
>Also does your average DVOM have enough power to get a cap to charge?
Short answer is no. Long answer:
Irrelevant as you need to check leakage which requires to apply a voltage close to the maximum rating in parallel with the cap under test and measure the series current. Should in the low micro amps if good. Generally not worth the effort to test just to find your 70yr old cap are junk. As I posted b4 replace the foil/paper and electrolytic caps. Leave the mica and ceramic caps, fail rate is low on these types.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 02-28-2018, 04:17 PM by Radioroslyn.)
They definitely were not built with the cheapest electronics. Try working on a GE form the same time period! They used the same wire wrapping technique and are even more difficult to work on. Zenith used goofy solder cups. It was all about streamlining manufacturing to cut costs. Yes, Predictas use couplates but so did everyone else in TVs and radios to reduce parts count.
That being said, they do have some weaknesses for sure. The push on/off power switches, tube sockets and original 21EAP4 picture tube are all prone to early failure. The Tenite picture tube safety screen also tend to fog over and smell.
Some of these were solved during the 3 year production run. They switched to better picture tubes and safety plastic and from series strung, hot chassis to a power transformer. The last, rarest Continental model is the best. Too bad Philco was bought out by Ford and production ceased.
The wire insulation they used gets sticky over time. I used isopropol alcohol to clean them ad the boards. Lacquer thinner sparingly on really stubborn spots. Very unlikey for resistors to go open. I suspect you are right bout not making good contact.
The big filament dropper resistor is also unreliable and probably gone bad. I replace them with individual power resistors like this.
That black disc is called a thermistor - a device thats resistance varies with temperature. It is there to give the set a "soft" power up. It should read about 440 ohms when cold and only a few ohms when hot. Beware - they get quite hot during normal operation. They are also unreliable, but still made and available from the major vendors. I can dig up the part number if you're interested.
Also yes, you are right about the Internet blowing things out of proportion. They sold many of these sets and I'm sure many were saved over the years because of their unique design. I also suspect many tried to fix them with very little knowledge of vintage TVs and quickly got frustrated and blamed it all on a poor design. The reality is that despite the unusual styling and component layout, the circuit design is typical of a late 50s TV.
Thank you guys, for all the information.... I have a quick question that maybe dumb but I have to ask... Im on Mouser's website trying to order caps, and it was asking me if I needed AC or DC caps. Does this set turn the voltage to DC at a certain point or is it all AC? I dont want to order the wrong caps.
Also the stickers are all missing off my Chassis is there a way to identify it? The Photofact references different models in a few places. I would be interested in the Thermistor. Im pretty sure mine is just straight through at this point.
Also I picked up a cheap tube tester I saw it for $7 on eBay, is it total junk? I figured maybe it would tell me if the tubes were good enough to get some function out of them.
What type of caps are you ordering ? Use plastic film caps rated in DC to replace the paper and "bumblebee" caps. I just get 630 volt caps for all EXCEPT for the 0.0015 uF cap in the vertical circuit. It MUST be rated for at least 1,000 volts!
You will get about the same voltage on either side of the thermistor. Especially if the tubes aren't lighting up. What resistance do you measure across it ?
Ametherm SL15 22101 it's 220 ohms cold and rated for 1 amp. That's the highest resistance rating I've found. you can put two in series to get 440 ohms cold. It's well suited for the 0.6A string in this set.
AWESOME NEWS!!!!! I was starting to doubt being able to do this. But I kind of gave my self some hope last night. Ive been pretty discouraged since the tubes stopped lighting. Well I replaced C1 because it was visibly leaking and I finally got a capacitor meter which showed it as shorted. Then I jumped out the Fusistor and I got A screen!!! Granted it was just white and had no sound just a slight hum. But it actually did something. Oddly enough after running it for a couple minutes the thermistor now reads correctly. I didnt get to check the filament dropping resistor yet. But the point is theres hope now. Im guessing since there's no real image and no sound I probably have no tuner? I slid back the rubber boot on the connector and back probed the wires while the set was running. I got 56V Ac on the White, 13v Ac on the Green, 22 V AC on the Red, 18V Ac on the Brown, and 375V on the Orange. Do those seem to be in spec? Also the tube in the tuner farthest from the knob is kind of Dim compared to the rest. The photo fact doesnt tell you what tube to replace it with though, and the GE tube in there has most of the writing worn off...
Radioroslyn where did you get those fusistors they look just like the originals?
>Radioroslyn where did you get those fusistors they look just like the originals?
pssssst! Can you keep a secret? They are originals! If you like PM me w/addr and drop one in the mail to you.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
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