Admiral 26R12 restoration

[bandersen]

Yeah! Another Admiral restoration project

This time it's the console on the left with a 21B1 chassis run #2.



It's a bit more primitive than the run #14 chassis I just restored. For example it lacks the couplates and gated AGC you'll find in the later runs. Also, it's not copper plated, but luckily, it's not rusty - just very dirty. It also has the original metal back.



Someone added crappy casters at some point. I'll be removing those.


Here it is up on the workbench.


Original owner ?



I found evidence of many old repairs under the chassis.

[bandersen]

First, I popped out the 5U4 rectifier and power it up. All the tubes lit up and I get what I expected on the secondary.

The flyback and yoke resistances check out OK too.


Uh-oh! Bad vertical output autotransformer
I was hoping I could find a break near the output lead and repair it. Nope.


Uh-oh! Bad vertical blocking oscillator transformer


Not to worry. Videokarma member kvflyer (AKA Don) to the rescue
The new transformers on the right just arrived in the mail and measure good.

[bandersen]

I'm almost done recapping and replacing many out of spec resistors. So many in fact, there won't be many original parts left in this set!

There are also many ugly old repair attempts. The horizontal oscillator and output circuit is a good example. Several resistors have been replaced with ones of very different values. A couple capacitors have been tacked in that aren't even on the schematic. Worst of all, the HOT cathode has been shorted directly to ground bypassing the 47 ohm resistor and filter cap.


Here it is cleaned up.


I've been testing all the mica caps with a Simpson 383A Capacohmeter. So far, they're all still good.

[bandersen]

The big 3K candohm power resistor is burned out.
I wonder if this 15W aluminum housed resistor will do if mounted properly ?

[kvflyer]

Bob,

I am very fortunate that my 26R12 was not hacked up like yours. Actually, when I bought it working from a guy about 20 miles from here, he told me it worked. He had quite an assortment of what I would call "Desirable" sets. Anyway, it did work so it was just a matter of replace caps, test, replace caps, test etc. I was lucky that all coils and transformers were good.

Just FYI, it worked fine for about 2 hours and then I heard a "POP" and the vertical collapsed to about half. I was not able to make it bigger with the height control (clue #1) but the vertical linearity did work. Voltages did not change whilst rotating the height control (more confirming clue #2). I tried lots of stuff and was unsuccessful so I put it down.

One of the guys, I think Dennis, at ARF suggested "tin whiskers" on the height control. Removing, cleaning the outside and the problem was gone. Lesson learned by me, remove controls, clean the outside a well as the carbon track and reinstall.

I have an NOS RCA 16TP4 in mine. Not aluminized so it isn't super bright. And I think I found out why it was NOS in the box for so many years. There are about three spots on the face where the phosphorus is missing. Factory defect. But you really have to look for them so, "No Worries Mate!".

Sorry if I hijacked your thread. It is nice to follow this thread...

[bandersen]

Not at all - comments are most welcome. This CRT is not aluminized either so I expect it will be quite dim compared to the Silverama CRT in the last set I restored.

[IsthmusTV]

Wow, that set sure had a lot of "issues." With all those hack repairs, maybe that's why they put casters on it

Fabulous work as usual, Bob.

-Clark

[Glenz75]

Great thread so far Bob - Lucky about getting some replacement vertical transformers, in all my TV adventures over the years I've only come across one that had an open circuit vertical blocking osc transformer. By the way I keep noticing that speaker on its front at the back of your bench, just curious as to why it just sits there? Is it one of those things that you keep meaning to move and forget about I have things like that on my workbenches..

[bandersen]

Originally Posted by IsthmusTV

Wow, that set sure had a lot of "issues." With all those hack repairs, maybe that's why they put casters on it

Fabulous work as usual, Bob.

-Clark

LOL - could be I confirmed that the sets current owner has tile floors so I'll be putting felt pads on the bottom. I just hope the holes drilled for those casters didn't crack the bakelite.

This set sure has been rather interesting to work on. I'd say the oddest "repair" so far was the addition of an extra 470 pF mica cap into the horizontal oscillator circuit where none belonged.
It the one turned around so no color dots are showing. I assumed that one of the originals must be bad, but, nope, they're all good.





I got around to checking all the tubes last night and was surprised to find there all quite good except for one. The 6AC7 video output tube shows a short on the plate so I'll replace it.

Originally Posted by Glenz75

...By the way I keep noticing that speaker on its front at the back of your bench, just curious as to why it just sits there? Is it one of those things that you keep meaning to move and forget about I have things like that on my workbenches..

Ah, that's a field coil speaker for an Admiral 20X1 chassis. I've been working on 3 of them in between these 21B1 Admiral chassis so I just left it up there for convenience. I really should put it somewhere safer though. I'd hate to tear the cone

[kvflyer]

Originally Posted by bandersen

...
Ah, that's a field coil speaker for an Admiral 20X1 chassis. I've been working on 3 of them in between these 21B1 Admiral chassis so I just left it up there for convenience. I really should put it somewhere safer though. I'd hate to tear the cone

When I have a speaker, now the first thing I do is to tape a piece of heavy corrugated cardboard cut to the exact size to the speaker over the front. Of course, it is easy to drop those needle nose pliers or screwdrivers just at the wrong time. They always seem to find the backside of the speaker.

[Reece]

kvflyer wrote: the first thing I do is to tape a piece of heavy corrugated cardboard cut to the exact size to the speaker
So do I, to avoid the great sorrow experienced more than once!

[kvflyer]

Originally Posted by Reece

kvflyer wrote: the first thing I do is to tape a piece of heavy corrugated cardboard cut to the exact size to the speaker
So do I, to avoid the great sorrow experienced more than once!

Yes, we (unfortunately) learn from experience don't we?

[bandersen]

OK, the speaker is safely stored away

I restuffed the electrolytics, finished recapping and installed the replacement vertical transformers.





The tubes have been installed and it's ready for a 1st test. The tubes wit green tape test OK, but just into the good range.

[Kevin Kuehn]

What kind of a tool do you use to peel open the bottom lip of those electrolytic can caps? I've tried a couple different things and always end up botching things up. That and I usually slip and I poke myself with whatever tool and get real angry.

[Electronic M]

Yea, what kevin said. I'm just as sick a' skewering myself as him....Also you do a neater job than me and I'd like to do as neat of a job as possible especially considering that I'm going to be getting a CTC-4 soon...