03-01-2018, 11:27 AM
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.
[Image: https://farm2.staticflickr.com/1675/2587...ef92_c.jpg]
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.
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.
[Image: https://farm2.staticflickr.com/1675/2587...ef92_c.jpg]
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.
