Moving down to V21. The Horiz. AFC section. Next up V22 the Horiz. Osc.

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Finished V22 tube the H. Osc.

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If you look at the lower terminal on the terminal strip in the picture above you'll should see that I replaced the single conductor shielded wire. I used some 20awg wire I had from when I wired aircraft avionics. Good stuff. The reason I replaced it was the center insulator was breaking down and crumbling away, thus creating a possible short between it and the shield. The same thing with the Phono input wire. This will get replaced also.

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I completed tube V9, V10, and V11. Video Amp, Video Output, and Noise Inverter.

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V13 and V14. 1st and 2nd Sound IF done.

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V15, V16, and V17 are done. Ratio Detector, AF Amp, and Audio Output. I replaced all the single conductor shielded wire. Some minor stuff to do then onto the IF section, then onto the controls.

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Reworked V5, V6, V7, and V8. The 4 IF stages. This pretty much completes the bottom of the chassis. There are still a few odds and ends to deal with, but over all it is finished.

Next up will be the front panel controls.

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I was looking at the schematic and in a dotted square is M7. Looks like a coil, caps, and resistor. I'm guessing it is the video detector. What is the chances the diode is good/bad? Is there a modern day equivalent? There is a cover on the topside that comes off and there is the diode.

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It is a germanium diode for sure. Getting hard to find. 1N60 is similar as are a few others. 1N34 are more common, good for crystal radios and other uses, but I don't know well they would work here.

Some are fine some are not... I generally see if the set works before I consider changing it. It is above chassis so it should be easy to change post assembly.

It appears the choice of a particular germanium diode type will produce only a small difference in detector efficiency:
http://www.rfcafe.com/references/rad...ruary-1952.htm

(scroll down to figure 7)

This is an early type germanium diode. You can use a digital multimeter with a diode check function to test whether it is functional. A good germanium diode shows a forward voltage drop of about 150...400mV, and doesn't conduct at all in the reverse direction (infinity reading).

Even though there are some special "video detector diodes", I've never seen any difference replacing them with random germanium point contact types I had on hands; you shouldn't either. If the original diode tests bad, just replace it with any germanium point contact diode. I am not good in Western types of diodes, but I think 1N34, 1N60, NTE-109 and many others should be OK.

I've always found germanium diodes to show signifigant reverse leakage when checked with an ohmmeter (compared to a Si diode's zero reverse leakage). Yet the Ge diodes always worked normally in service.

It may depend on what voltage your ohmmeter applies.

I've never tried it but what about a Schottky diode. They have a quite low forward bias voltage. Just a thought.

Thanks guys for the suggestions. I have some 1N60 and some 1N914. I'll try them once I get the set working.

I changed some resistors that were in some if the IF cans and in M7. Basically, they were 5% and each one was 10-11% out-of-tolerance.

Here is the schematic of the 2 IF cans that had resistors. L32 and L33. Both in the 1st IF stage. Each of these 2 cans had capacitors along with M7. And each can used different types of capacitors. I'll show some pics.

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Here is L32. The 22K resistor was 10% out-of-tolerance and was replaced with a 1W 22K 5% carbon film resistor. The caps were disc.

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Here is L33. The 4.7K resistor was 11% out-of-tolerance and was replaced with a 1W 4.7K carbon film resistor. The 2 caps were a dual mica cap. This cap used mica film just like a trimmer cap. I tested the 100pf side and got 102pf. I couldn't test the 13pf side due to my checker doesn't go down that low.

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And finally M7. See schematic in a few previous posts. The 8.2K 5% resistor was 7% out-of-tolerance and was replaced with a 1W 8.2K carbon film resistor. Both Riders and Sams schematics showed M7 using a 10K resistor. I decided to use what was actually used. The caps in this unit were like "dogbone" type. Again all 3 cans used different types of caps.

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Working on getting the chassis all cleaned up. I scrubbed and wire brushed the chassis and then shot some primer over the pitted areas from the mouse pee. Once the primer was dry, I used some Bondo Glazing putty to fill in the pits. Tomorrow I'll sand the putty and then primer and paint the chassis.

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The glazing putty has been sanded and now on to the primer.

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While the paint on the chassis dries I turned my attention to the tuner.
I cleaned it up and used DeOxit on the wafer switches. I also replaced all if the resistors. There were 12 of them. 9 were clearly out-of-tolerance. Some as much as 47%, while 3 were in tolerance. They were replaced with 1W Carbon Film resistors.

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Other than it looks much better, why did you replace the insulated wires in the tuner?

Also, based on the time of your replies, when do you sleep?

If you're talking about Christ he probably sleeps between 11 pm and 7AM based on post time stamps in his time zone.... if he is retired he doesn't have to optimize things for a work schedule.... nothing unusual the way I see it.

Very nice work (as usual). Some of those resistors in the tuner must have been a pig to get at.

No doubt he was super careful not to nudge or deform any of the coils.

Tom,
They were replaced because some were cracking. So I replaced them all as a precaution.

Usually between midnight and 8am.

Correct! I am retired now 4 1/2 years.

Thanks. Yes they were. But the paint had to dry on the chassis so it was a good long task that I could take my time.

Correct.

With the paint dry I could move on. Got a lot done today.

I finished the front panel controls. I decided that the "extra" Tone control and TV/Phono switch could be relocated in the extra hole when I moved everything to the left. Of course this control isn't accessible from the front pencil box, but that's ok. I'll use it to set the tone control on the bench. BTW, I eliminated the TV/Phono switching. Our TV never had it. I shortened the shaft so it would not hit on the front of the cabinet.

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Then I had to shorten the Local/Distance switch mount. When I first tried the chassis in the cabinet, the switch was right up against the pencil box and needed to be moved a little further aft. I cut off the mounting ears and shortened the mount about 3/8". Then bent up some aluminum and bolted them together. Worked out real well. If it is too far aft, I can use some small spacers between the mount and the chassis.

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I then moved on to mounting and wiring in the tuner and clearing off all the extra masking tape.

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Today I cleaned and checked the tubes. There were 4 that were bad out of the 25 tubes. One just checked into the green. Those five will be replaced.

I then reinstalled the CRT wiring. I placed clear heat shrink tubing around each wire where it went through the chassis for protection.

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I then redid the 2 terminal strips on the top of the chassis. One included the .25A fuse.

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I then turned my attention to the Flyback and 1B3GT connector. I replaced the 3 220K 2W resistors with 3 220K 3W resistors. After looking over the Flyback a little closer, it looks like the mice tried to make a meal out of it! They also nibbled on the filament wiring to the 1B3GT connector.

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I'm re-coating the Flyback windings with some Super Corona dope as I type. A few more coats and it will be ready to put back into the chassis.

While you're at it change the HV rect filament winding...That much chew is likely to arc through. Better to do that now while it is easy to get at.

Did you verify that the flyback secondary (the 'tire') has continuity (just to be sure the rodent critter didn't nik the winding)?

Yeah I did. It ohmed out pretty close to what was on the schematic.

Tom,
Good idea! I changed those wires too.

Before replacing the HV rect filament wire, make sure that it's made out of copper (not an ohmic wire).

Did anybody other than Zenith use that?

I don't know exactly about US-made sets but I met 'ohmic' HV heater windings in some early Russian televisions. Just a precaution to be sure that it's not your case.

Mine uses wire. It does use a 3.9 ohm resistor. Which was replaced.

Today I tackled the HV cage mod. I cut away the corner and made a triangular filler piece. Then cleaned it up and painted it a silver color. I wanted it a bit different color than the chassis.

I then finished up wiring the HV cage. I replaced all the HV wire, except the HV lead to the CRT.

Then I could finish up wiring in the Yoke wires. All done except the 300 Ohm twin lead from the Tuner to the terminals. Then on to first power up.

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The suspense is killing me.