Early 50's set, Is this missing the deflection yoke?

[cbenham]

Originally Posted by Magnavox300

I am considering buying this set, and this maybe an obvious question,
but is this missing it's deflection yoke?
I see something inside a box on the chassis that looks like a yoke, I just don't know. Looks like an early 50's set. Magnavox300

The piece with the long bolt stickiing out is the permanent magnet focus unit.
Between it and the bell of the CRT is the yoke, with wires running from it to the HV cage. Hope you get it and make it worka again. Good Luck,
Cliff

[electronjohn]

Love the dueling 5U4s atop the PT.

[holmesuser01]

Originally Posted by electronjohn

Love the dueling 5U4s atop the PT.

Me, too. I've never had a TV with them in the PT, until I got my RCA roundie CTC-7.

I want to see more pictures of the OP's set!

[peverett]

I have some Hoffman Mark V chassis sets with 1 5u4 mounted on the transformer, but not 2! I also have a 1937 Philco Radio with the rectifier mounted on the PT.

[lnx64]

Originally Posted by jr_tech

Here is a picture of my 1953 17" Philco... The yoke is seen ahead of the focus magnet, touching the bell of the CRT, but has no exposed windings wrapping over the bell. This is typical of 70 degree or smaller angle yokes of the period.



jr

What is that long thin copper colored thin coil going from the yoke to the socket of the CRT? Looks like a super long warped screw.

[dieseljeep]

Originally Posted by lnx64

What is that long thin copper colored thin coil going from the yoke to the socket of the CRT? Looks like a super long warped screw.

That's a flexible shaft to adjust the focus. They did it, so you didn't have to remove the back. There should be a hole in the back where it protrudes.
Made of the same material as the old speedometer shafts.

[dieseljeep]

Originally Posted by peverett

I have some Hoffman Mark V chassis sets with 1 5u4 mounted on the transformer, but not 2! I also have a 1937 Philco Radio with the rectifier mounted on the PT.

The Hoffman UHF models had 2 5U4's mounted the same way.
Also, the larger screen sets, where the B+ demands were higher.

[Tubejunke]

Originally Posted by dieseljeep

The Hoffman UHF models had 2 5U4's mounted the same way.
Also, the larger screen sets, where the B+ demands were higher.

I know that two 5U4 tube rectifiers represent a four diode smoothing of the AC waveform. I wonder if the old sets more commonly used plain full wave, full wave bridge, or perhaps even doublers. Maybe a little of all of them. Just curious.

[Eric H]

Originally Posted by jr_tech

Here is a picture of my 1953 17" Philco



jr

Interesting that it has an Electromagnetic Speaker instead of a PM, 53 seems awfully late for that.

I have a 53 but the speaker is located in the bottom so I don't think I've ever looked at it all that closely, don't know what it is.

Those Cotton Straps holding the Yoke get very brittle, I broke one of mine when I changed the CRT just by bending it sideways, snapped off like it was made of Pasta.

[jr_tech]

I just checked my 17 inch 1953 console... the 4 wires going to the speaker (10" or so) look exactly the same, but the speaker has a choke mounted to the frame. The UHF tuner is hardwired to the chassis on the console, while in the table model the power for the UHF is taken from an adapter plugged in to the audio output socket (with the tube plugged in on top of the adapter). Both sets are early production '53 models, and were purchased before Christmas 1952.

Thanks for the "heads up" on the weak straps! I will be careful If I ever have to mess with them.

jr

[jr_tech]

Originally Posted by lnx64

What is that long thin copper colored thin coil going from the yoke to the socket of the CRT? Looks like a super long warped screw.

That is the adjuster for the permanent magnet focus assembly. The field is adjusted by sliding a "shunt" in or out, the flex adjuster (which normally sticks out of the back of the TV) turns a screw, which slides the "shunt".

jr

[dieseljeep]

Originally Posted by Tubejunke

I know that two 5U4 tube rectifiers represent a four diode smoothing of the AC waveform. I wonder if the old sets more commonly used plain full wave, full wave bridge, or perhaps even doublers. Maybe a little of all of them. Just curious.

You'd have to look at the schematic to see how they're connected. Sometimes in parallel, or each one connected, half wave. They also used two rectifiers using two high voltage windings to obtain two different voltage sources.