1951 AMC 16" TV Restoration
 

Guys,
I've just started on this TV. First a little history. It was bought in 1951 (the year I was born) at a department store in downtown Cleveland Ohio named Higbee's. This store was the downtown store in the "Christmas Story" where Ralph sees the Red Ryder BB gun.

I saw that it was for sale and bought it. The guy selling it said it was his uncle's and told me the story of where his uncle bought the TV. Well I'm from Cleveland Ohio and that's the connection. I had to restore the TV.

I got the Sams #111-3 and the Riders Volume 5 page 1 for reference.

I checked the CRT, a 16KP4, and it took about 1/2 hour to come up into the middle of the green on my BK 467. Not great, but it looks like it will give a decent picture.

I pulled the chassis and installed some 1/2 x 1 inch nylon "feet" so I could grip the chassis to flip it over and the nylon prevent the bench from getting all torn up from the original mounting screws.

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I then removed the picture tube for safe keeping. Then removed both the HV rectifier and low voltage rectifier tubes. I put it on my variac and brought the voltage up to 40vac while checking the current draw. Less than 1/4 amp - good. After awhile I added more voltage to check to see if the tubes would glow. I got up to 70 volts and all the tubes that were plugged in glowed. Enough of that.

I then decided to pull the tubes to check them. I used the SAMS tube location chart nad began pulling tubes, verifying that the correct tubes were installed, then marked them with a small piece of masking tape. When I got to V7 the Detector tube, there were 2 tubes in its place! Whoa, I didn't see that coming. Both Sams and Riders showed a single 6T8 tube. I have a 6AQ6 and a 6AL5 tube. I'm pretty sure this is a factory mod or update. Now I need to find the correct schematic and documentation, if its out there. I included a picture of the 2 tubes on top and below the chassis.

Also there was a 6V6GT instead of a 6K6GT for the vertical output.

I also have a question on "something" that is sticking out of the "back" of the HV cage that is attached to the Flyback transformer. At first I thought it was a fuse. But it looks like the 1/4A fuse in mounted below. Though I'd have to check for sure. What is that something? I've included a picture of it.

The chassis is pretty clean but real dusty. I'll spend some time cleaning it up before I go much further.

I also will research the dual tube modification.

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Here's the schematic from Sams.

Gotta be factory, the hole was punched when the chassis was just a piece of sheet metal.

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What you are seeing is the flyback core and retaining clamp.

http://www.videokarma.org/attachment...1&d=1468077669

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Cool..."Higbees". The "Old Man" must've bought that to replace the console radio in "A Christmas Story":)

Chris - did you seam those pages together, or do you have a scanner that will do 3 pages at once? What model scanner did you use?

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I seamed them together using my CAD program. DeltaCad.

I used my cheap Lexmark X1185 printer/scanner. I only use it to scan though.

Yup, now that I have time to look a little closer. Thanks.

That's a Muntz design with a handful of parts thrown back in. Unless I'm blind, I see no mechanism for blanking the screen when the phono input is selected.

The switch for TV/Phono input is a simple SPDT slide switch. It does look like the TV picture is not turned off. When I get it up and running, I'll check its function.

There's a capacitor in the bottom with the Bendix name on it. That's probably who made it. Only two IF stages. :boring:

Oh yeah, it's made by Bendix that's for sure. Why do you say that 2 IF stages are boring?

Better quality TVs had three IF stages (like my Dumont RA-103), or even four (like my RCA CT-100). More IF stages means more amplification of the incoming signal, resulting in greater sensitivity (ability to pull in weak, far-away stations). A TV with only two IF stages would only have worked well in a metro area with nearby stations.

Sensitivity per se is not such a big deal nowadays, when many collectors feed their restored TVs from a DVD player or whatnot, with a nice strong signal. The number of IF stages can be interpreted as a sign of overall quality, however. If the manufacturer skimped in that area, they may have skimped in others, too.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Phil,
Thanks for the explanation. I can see where if they scrimped here they could scrimp there kind of a deal.

When I'm done I'll for sure include some videos of the picture and sound quality.

Again thanks and I enjoy reading over your restorations both radio and TV.

Here some more pics. I cleaned the chassis with some mild dish washing detergent. It wasn't real dirty and it cleaned up pretty well.

I checked the tubes and some are weak and some are very weak!

I then got to work on making and ID on every capacitor and resistor and comparing it with the schematic and parts list. There were some discrepancies but nothing real major. I use a small block of masking tape and mark each component. While doing this I check the schematic and parts list. I then make the document changes in red ink.

I also drew out the 2 tube configuration for the listed 6T8 tube. Besides using 2 tubes, there were a few resistors and capacitors in the chassis that weren't in the schematic. I'll update my parts lists accordingly so I get my order right.

I'll draw up the new configuration and I'll post it side-by-side with the schematics so we can see what the changes were.

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Even the Muntz had three IF stages. Boring was just a poor attempt at humor. :sigh:
It seems, at the time, just about every set manufacturer used at least three stages of IF.
Bendix also designed the 12" set, using the 6BG6 reflex circuit horizontal osc and output and the damper less hv sweep circuit.
Muntz copied that design, not the other way around. :scratch2:

In order to get fine detail resolution in the pic, the IFs have to be stagger tuned. And stagger-tuning reduces overall gain. Add another IF stage for more gain, and you can stagger-tune for a wider IF bandpass, allowing finer detail resolution. So more IF stages equals better fine detail in the pic.

(Then into the 1960s, high gain IF tubes were developed (e.g., 6EH7, 6EJ7) which allowed good bandpass with just two IF stages.)

That set is a Bendix set. The 2 tube sound mod was due to the FCC allowing TV stations to reduce their Aural power to a percentage of the Visual power. When that happened, some sets, including your Bendix, with only 2 IF stages, had low sound, if they were located in B or worse coverage area. Some companies marketed a 2 tube "kit" to boost the sound. broadcaster

Was that with the advent of intercarrier sound?

Well I traced out the audio circuit and drew up the changes. I'll attach a pdf of the "before" and "after" the audio mod was done at the factory.

Some comments are in order.

1) SAMS made a mistake and reversed the polarity of Cap C3. This was confirmed by looking at the picture of the resistor location in the actual SAMS folder.
2) I eliminated the extra switching shown on the schematic showing switching for a combo unit. Mine is a table top model.
3) With the audio mod there were 3 components added not counting the tube. R79, R80, and C64. I gave them these designations to continue with the SAMS.
4) R37 was changed from 82K to 1.5MEG, R35 from 10MEG to 5.6MEG, R32 from 12K to 13K.

As a general observation, I noticed that about 10 to 12 resistors are different values from the schematics. Consistent was the change from 47K resistors to 39K and 12K to 11K and 13K. Could have been caused by parts shortages?

You guys that are more knowledgeable than myself, could you look over what I drew up and give me your comments? I drew up what I saw on how the chassis was wired.

Thanks.

It's more likely there were parts shortages due to the war going on in Korea at the time. Big brother got first dibs on everything. All the best, Tom

The was my first thought!
There was several firms that didn't use 6T8's. Admiral, RCA, Motorola to name a few.

Looking at your under-chassis view and the schematic, I noticed a low current selenium rectifier in the horiz yoke circuit. That's a new one on me!
I wonder what the reason was? :scratch2:

I wondered about that little selenium too, thinkin' maybe it was a neg.bias supply. But couldn't spy it in the schematic. :saywhat:

That's a centering circuit, you found it used alot in newer sets most noteably color sets. The late Jack Darr service editor for Radio-Electronics gave a good description on it. Still trying to find the artical. All the best, Tom

CT-100 (and TRK-12) have FIVE IF stages!

Yes, more gives more gain.. BUT ... it also allows a more sharply
tailored bandpass curve with a very sharp 4.2 MHz cutoff.
Doing the sharp bandpass edges cuts overall gain.

The last day or so was spent taking inventory of what parts are needed and making a list and where to get them from. Some I had "in stock" while others will be ordered from Just Radios and Digikey. I've decided to bump up the 1/2W to 1W, the 1W to 2W and the 2W to 3W. Some of the 2W resistors seemed a bit discolored and heat stressed so those 3 will be replaced with 5W (R70, R71, R73). There was one resistor clearly bad. It had split open due to excessive heat. It is R76 a 470 ohm 2W resistor. This will be replaced with a 470 ohm 10W resistor the local parts house had in stock. It will still fit nicely in the chassis.

I'm using the taller, slender Nichicon 105c E-Caps so they'll fit into the cans. There are 2 cans with 3 each caps in them

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While I wait for the parts to arrive I'd like to clean up the HV cage. Never having done a TV before with a flyback I could use some guidance. I want to clean this up and of course replace the 2 680K 2w resistors with 2 680K 3w resistors and the .00047 10Kv cap with a .00047 15Kv cap from Just Radios.

It liiks like I could remove the cage portion by unscrewing it from the chassis, removing the flyback mounting screws, and the 1 screw holding the phenolic standoff. Once that is removed I can access the the electrical parts. Here's where I could use some help. I'm thinking of removing the wires from the flyback phenolic board and releasing the clips on the 1B3GT tube socket to completely remove the "guts" so I can work on them on the bench.

My other option is to unsolder the flyback wires from underneath the chassis instead of from the flyback board. I've included close up pictures of what I have to work with.

Also there is a very small separation of the flyback tape on the top of the flyback. Should I look at repairing this or just leave it alone?

What should I use to clean the whole thing off with? I usually use some rubbing alcohol, Q-tips, etc.

While I have it out, is there anything else that needs to be done to it?

Thanks.

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Avoid unnecessarily doing anything around a flyback. Those thin wires are very prone to damage.

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Unless there is a clear and present need for removing the flyback, such a major hysterectomy is ill advised. :eek:

OK guys. Then do I just clean it the best I can in place using alcohol and Q-Tips?

I decided to work on re-stuffing the existing E-Caps. After I took careful notes on the wires etc, I removed them. After I cleaned the contacts up I took them to my band saw and sawed off the bottom portion of each cap just above the mounting base. Then I used a deck screw and a heat gun to pull out their guts. More heat and a craft stick to gouge out the tar. Some acetone and a wire brush and they were clean. I then trued up the bases using my flat plate sanding bar. Then the tops were trued up using my disc sander and miter gauge.

I then used some 1" thin wall sprinkler pipe with the end trued up like the tops, then it was cutoff 1" long. Then another end trued up, then cut off at 1" again. This gave me 2 pieces of thin wall tubing 1" high with 1 end trued up that I'll use as sleeves. The trued up end will be epoxied to each base.

I cleaned up both bases and sleeves and epoxied them the sleeves to the bases using 15 minute epoxy. I carefully positioned each sleeve to be centered between the walls. The epoxy was applied only to the inside so the epoxy won't interfere with the tops when assembled.

When the epoxy is dry tomorrow I'll polish both tops and bases. It's easier to polish the base because I can grip the sleeve!

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After I prepped the E-caps I decided it was time to clean the HV cage. I used alcohol and some places acetone. A lot of Q-Tips later this is what it looks like. I still have to change out the 10Kv cap when my order from Just Radios arrives. The HV cage looks a lot better. I also have to re-solder on the 6BQ6GT grid cap back on the wire. It was hanging on by a few strands when I got the TV.

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The epoxy has dried and I polished out the E-Caps cans. I've included a picture of how they will look assembled. The seam is almost invisible. The friction of the sleeve is all that is needed to hold the tops in place.

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Great looking job on those cap cans. I've never seen anyone do them so well.

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Thanks Jim.

I re-dressed and re-soldered on the plate cap clips for the 1B3GT and the 6BQ6GT tubes in the HV cage. I made sure there were sharp points. The reason I did this was the plate cap for the 6BQ6GT had fallen off. The wire strands were broken. The plate cap for the 1B3GT was hanging on by just a couple of strands.

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My E-Cap order came in so I finished up re-stuffing them. Each can holds 3 E-Caps. I used Nichicon slender caps where I can. Each can was able to hold the 3 caps next to each other. No stacking. I use hot glue to glue the 3 caps together with the negative leads close to each other. I then connect the negative leads together and use some solid 22awg 600V wire for the leads. I attached them using the coil method. I then form each lead to make up a bundle coming out from the approx. center. This bundle is laced tied to give it some extra strength. The leads are trimmed and stripped before I insert the caps into the sleeve.

A generous bead of hot glue is placed around the bundle then it is inserted through a 5/32 hole drilled in the bottom. The assembly is held in place till the hot glue sets up. Then the caps are tacked to the wall of the plastic sleeve. The leads are soldered to the contacts. The ground lead is left unattached. It will be connected to the can after it is inserted into the chassis.

I place the cans back into the proper position into the chassis. I then solder the "twist" tabs to the chassis. I'm afraid that they will break off if I twist them. Then the ground lead is attached to one of the tabs soldered to the chassis.

When all done, I'll slide the cans over each assembly to finish off the chassis.

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I got some more done on the chassis recapping.

I changed out the cap "C46" and resistor "R62"on the "Contrast" and "Horizontal Hold" control.

I then began recapping and rewiring the fuse and selenium rectifier. I'm using a terminal strip for each. I'm using pigtail fuses. For the rectifier, I'll wire the original selenium in then get some voltage measurements, then change it out for a 1N4007 diode. Then I'll adjust the existing 22 ohm resistor "R77" to match the correct voltage needed.

I'm needing my .2uf 630v caps from Just Radios to really get into recapping. The caps are "layered" and I'm not going to do much till I have all the caps on hand. There is some that I can do though. Just a limited amount.

I also changed out another cap "C54" and one of the heat stressed resistors "R77".

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