Admiral 20B1 combo restoration

[kvflyer]

Nice work as usual Bob. Just watching this forum and the Antique Televisions forum on the Antique Radio Forum has really opened my eyes with regard to trouble shooting. At the risk of being too simplistic, it seems as though the usual problems are almost always the same issue. Capacitors! And of course, resistors drifting high.

I suspect you guys are bringing sets back into use faster than some of the average "repair" shops back in the day. I know that we have two distinct groups who on one side of the coin are against total replacement of capacitors. They want to trouble shoot. And then there is the other camp who believes that most if not all paper and electrolytic capacitors are already bad and should be wholesale replaced.

Guess that is what makes the world go around... different opinions.

Again, great looking results so far. Thanks for taking the time to share your success with us.

[bandersen]

I'm actually firmly in the camp of wholesale capacitor replacement. The reasons I didn't here was that the seller had already fired it up and it makes for a more interesting youtube video series.

I started going through the chassis more thoroughly last night and was surprised at how far out many resistor are. Some as much as 5X the specified value. Those will all get replaced along with the remaining paper, electrolytic and mica caps in the audio IF cans.

That would be a 30 pF and 35 pF cap in this revision. They are exposed to the air and can develop SMD.

[bandersen]

Here are the new mica caps installed. That plus a sound IF alignment should do the trick.

[M3-SRT8]

I think the debate regarding wholesale electrolytic and paper capacitor replacement is pretty settled in favor of... Total replacement.

What's the alternative? Leaving 60 + year old capacitors in the chassis so they can blow up, taking the power transformer and fly back with it?

[Kevin Kuehn]

I think there's at least a third camp that sometimes enjoys trouble shooting with original caps, but eventually replaces all paper and electrolytics. For some folks the troubleshooting is the fun part.

[M3-SRT8]

Originally Posted by Kevin Kuehn

I think there's at least a third camp that sometimes enjoys trouble shooting with original caps, but eventually replaces all paper and electrolytics. For some folks the troubleshooting is the fun part.

That's my camp. I enjoy restoring - by section - a vintage tv, powering up as I progress, seeing and hearing it's effects as I go.

But, it's merely one of the original two camps, as all the caps are eventually replaced.

[bandersen]

I just received my order from Allied Electronics with the last few parts I need for this set. While I was at it, I stocked up on common values.

Illinois Capacitor brand 0.047 @ 630V axial metalized polypropylene with 1-3/4" leads only $0.38 each

[bandersen]

I finished work on the lower chassis and all but a few electrolytics on the upper chassis.

There were very convenient tie points so I didn't bother restuffing the cans.


So now I have much better volume but it's distorted. Hopefully an alignment will clear that up.

Also the vertical linearity is terrible. The middle is stretched while top and bottom are squished,

I'm hoping replacing the vertical output tube cathode bypass cap will clear that up. This is actually the best I could get by adjusting the height and linearity controls.

[bandersen]

replacing the electrolytics in the vertical circuit helped, but it still bulges in the middle.


I track the problem down to the sawtooth at the grid of the vertical output tube. I'll double check the vertical oscillator circuit.

[Down Under]

Good luck with that linearity issue, I've got the same issue on one of mine. Luckily not quite as bad.

Cheers,

Adam

[bandersen]

I switched gears for a while and completed an alignment. A little peaking greatly improved the sound and I was surprised to find the video was way off.

Them went back to the linearity issue. Here's the best I've managed to get so far.

[kvflyer]

Originally Posted by bandersen

I switched gears for a while and completed an alignment. A little peaking greatly improved the sound and I was surprised to find the video was way off.

Them went back to the linearity issue. Here's the best I've managed to get so far.

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Well Bob, "That ain't bad!" Actually looks pretty good. Congratulations.

[bandersen]

The owner stopped by and picked up his restored chassis early this evening. Not only did he put a little cash in my hand, he also left behind some goodies



This homebrew "kinescope Tester" looks to be well made.


The RCA WR-39C Television Calibrator could be fun to try out if I get the matching sweep generator.


This is a nearly restored Admiral 21C1 chassis.


Supposedly the 16KP4A is barely used.


Someone really put a lot of work into this set and used a bunch of Sprague Atoms


I'm thinking I can get it working and slide it into this 16R12 cabinet. The chassis currently in it is unrestored and the CRT has a shorted cathode.


Finally, three organizers full of NOS parts that I'm sure will come in handy.

[bigaudioal]

Nice!! Congrats on that combo restore too. Looked great in the final video.

[kvflyer]

I hate you!!

Just kidding, and I am happy for you. Mostly because this stuff didn't go to the dump as much of it did a few years ago.

Can we ever have enough "Stuff"? I snag any old test equipment because it is usually cheap. Good for a source of parts; knobs, tubes etc...