Working on an Admiral 20X12

[Kamakiri]

The bottom of the horizontal oscillator's just a mess. Here's a shot of that, and another shot of the section. The orange drop was done by the last person that worked on it, I should probably change it out just because......

[Electronic M]

If the osc. coil is out of range I'd check the resistors and try replacing that orange drop...If that fails see if adjusting the other slug of the osc. can gets you anywhere.

[old_coot88]

Have you tried adjusting the horiz. range trimmer, designated B2 in Sams? It's located on the rear chassis apron, next to the horiz. drive trimmer (just to the left of it).
Also there's two resistors, R75 and R76 (68K and 120K respectively), coming off either end of the horiz. hold control. Either of those being off value will affect the range.

What value is printed on the Orangedrop cap? Is it .002 mf?

[Kamakiri]

I didn't try the range because I was assuming that it was a frequency issue.....can't hurt though

The orange drop was a .002. I changed them both, no change in performance. I'll check the resistors tomorrow. I'll get back on the 8TS30 as well

[old_coot88]

Originally Posted by Kamakiri

I didn't try the range because I was assuming that it was a frequency issue.....can't hurt though

It means `frequency range`, like a coarse adjustment, with the H.hold being the 'fine adjustment'.

It looks as though sumbody was working on this problem at length, then gave up on it when that Lin coil blew.

[Kamakiri]

Well, I've spent time over the last couple weeks on this set and got basically nowhere. This morning I got up at about 3:30 AM after falling asleep at about 8:30 PM last night, I had a full head of steam and decided to tackle this set, do or die.

I disasembled and tested everything in the entire horizontal circuit, found one missing cap on the width coil (this set was pretty botched up before I got it), and no change. After testing about a dozen resistors and replacing a couple that were way out of tolerance, still no change.

Then I noticed a couple green spots of corrosion on the back side of the width coil, where I couldn't have seen them before. Looks like a couple turns are shorted....which would explain why the turning the width coil does absolutely nothing. That, and the fact that the horizontal lin coil, which sits right below it, was corroded and open, leads me to believe I need a width coil. Spec on the Sams is .1 ohms, this one reads about 1.3 ohms.

I'll pick this up after I get one......

[decojoe67]

Good luck with it. Sometimes you get those sets that just play flawless with a re-cap and others have all sorts of issues. I guess it's the conditions they were stored in that determines that.

[Kevin Kuehn]

When you're talking 1.2 ohms error, make sure your meter was able to zero first, and that the terminals on the coil are clean(maybe re-solder them) It doesn't take much contact resistance and you end up with a false reading.

[bandersen]

Even when working correctly, the width coil has very little effect. From one extreme to the other it will change the width maybe an inch or even less. The with coil is in parallel with the flyback coil and used to tweak it's characteristics.

BTW that photo you posted earlier of the bottom of the hor. osc. circuit is stock. Admiral made really wired it that way with three resistors connecting together in mid-air.

[Kamakiri]

Yep, I figured that out by the schematic. As I said, I tested every resistor in that entire string. Since the width control does nothing and I have inadequate width, along with the resistance of the coil, I figured that would be the next step. Terminals were definitely clean, as I de-soldered and cleaned the ends of the wires to the coil.

These sets are never this difficult!

[Kamakiri]

Welp, she's working great now!

The problem turned out to be a simple one. Whoever was futzing around under the 6BG6 (probably before I was born), cut a cap out of it that I couldn't even see. Looks like someone back then was testing things and just gave up. That, and the width coil out of a parts set (thanks bgadow!) brought the set back to life!

Horizontal lin's a little off, but I'll play with that after a little usage.

And finally, another tough dog is done. Whew.

[baursam]

Well done Tim!!! Perseverance! !!

[old_coot88]

Kudos to you Sir. Good job! Of course I'm curious which cap it wuz.

[Kamakiri]

It was a .2 uF 200V cap anchored to a dead pin on the 6BG6 going to the ground on the filter can closest to the tube......