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-   -   Admiral 26R12 restoration (http://www.videokarma.org/showthread.php?t=252865)

bandersen 12-17-2011 02:48 AM

I too have a few scars on my left hand from various tools slipping. Here's what I'm currently using. I start off with the pocket knife.
If that can pry up a little section, I move on to the small screwdriver. If not, I use the pliers. Note they do not have serrations so they don't chew up the aluminum all that much.
http://farm8.staticflickr.com/7147/6...7c91779f_z.jpglickr

bandersen 12-17-2011 02:56 AM

I powered the set up slowly and all seemed OK so I went for full power. I was really surprised to see a distorted image. A little control tweaking and I got a stable image :banana: Those relacement vertical transformers are working just fine :yes:

Barely any sound though :scratch2:
http://farm8.staticflickr.com/7027/6...9bb6946e_z.jpg

After a little investigation, I discovered a broken antenna lead. Fixing that helped a little.
http://farm8.staticflickr.com/7161/6...aa790c91_z.jpg


Then, I tried rocking each tube in it's socket and, bingo!, a 6AL5 wasn't making good contact. Plenty of sound now :music:
http://farm8.staticflickr.com/7015/6...1ddd1da6_z.jpg

Next, I hooked up a better signal source. The picture is pretty good, but rather dim. Not surprising really for an original CRT.
http://farm8.staticflickr.com/7173/6...d397a0f1_z.jpg

I switched to a dead channel and I have vertical bars similar to the last set I restored with the same chassis. This time there's one pronounced stripe and several faint bars.
I'll do some troubleshooting over the weekend. All in all, a very successful first power up :)
http://farm8.staticflickr.com/7172/6...b2edfdbf_z.jpg

Eric H 12-17-2011 03:03 AM

43-08 54th st
I wonder if this is where it originally resided?

http://maps.google.com/maps?q=43-08+...270.12,,0,0.05

dieseljeep 12-17-2011 08:43 AM

Quote:

Originally Posted by Eric H (Post 3021554)
43-08 54th st
I wonder if this is where it originally resided?

http://maps.google.com/maps?q=43-08+...270.12,,0,0.05

Could be Kenosha, Wi.:scratch2:

Eric H 12-17-2011 12:13 PM

Quote:

Originally Posted by dieseljeep (Post 3021565)
Could be Kenosha, Wi.:scratch2:

Kenosha?

N.Y. was the only one I found with a 43-08 in the address but then this is sixty years later.

Kevin Kuehn 12-17-2011 05:03 PM

Quote:

Originally Posted by bandersen (Post 3021553)

I switched to a dead channel and I have vertical bars similar to the last set I restored with the same chassis. This time there's one pronounced stripe and several faint bars.
I'll do some troubleshooting over the weekend. All in all, a very successful first power up :)
http://farm8.staticflickr.com/7172/6...b2edfdbf_z.jpg

In case you haven't seen this yet over on ARF... mbear2k posted a link to a scan of his Admiral notes from Rider. Take a look at page 4. Still no value for the RF choke, but maybe it's the same as L405 used eleswhere in the circuit? It does identify the three componets being available as a combined filter(part #A34596).

http://www.oldtubes.net/library/free...ures-hirez.pdf

Kevin Kuehn 12-17-2011 05:39 PM

I guess he posted it here too. Great stuff.

http://www.oldtubes.net/library/free...uble_Cures.pdf

bandersen 12-17-2011 08:00 PM

Thanks for the link. Adjusting the drive got rid of the line but I still have the faint bars.

bandersen 12-18-2011 01:31 AM

Quote:

Originally Posted by Kevin Kuehn (Post 3021589)
In case you haven't seen this yet over on ARF... mbear2k posted a link to a scan of his Admiral notes from Rider. Take a look at page 4. Still no value for the RF choke, but maybe it's the same as L405 used eleswhere in the circuit? It does identify the three componets being available as a combined filter(part #A34596).

Hmm. I don't see L405 in the parts list for the 21B1 chassis.

It says the RF choke is part # 73B8-3. I checked in my Thordarson cross reference, but it's not listed.

Does anyone have a cross reference guide for other suppliers like Merit or Stancor they can check ?

bandersen 12-18-2011 01:42 PM

Using the notes mbear2k posted, I was able to completely eliminate the retrace lines :)
http://farm8.staticflickr.com/7161/6...bd5390347c.jpg http://farm8.staticflickr.com/7011/6...c484e3580d.jpg

I also put a scope on the horizontal output tube's grid and saw this.
There's some ringing in the waveform that most likely accounts for the vertical bars on the left.
http://farm8.staticflickr.com/7015/6...2d948c0bea.jpg

The signal at the preceding stage (horizontal oscillator) looks correct so I'm not sure where it's coming from.
http://farm8.staticflickr.com/7028/6...a902c24f2f.jpg

Otherwise, the set is playing fine, just a little dim and washed out. I may try rejuvinating the picture tube :scratch2:
http://farm8.staticflickr.com/7171/6...cde55feb3a.jpg

bandersen 12-18-2011 02:55 PM

A little web searching pulled up this thread describing exactly the same problem and some solutions: http://www.antiqueradios.com/forums/...p?f=3&t=108670

I put my scope probe near the yoke and found really pronounced ringing.
http://farm8.staticflickr.com/7175/6...7972fd7810.jpg

I flipped though some 21B1 schematics and found the last revisions which did include that filter as part of normal production. No values given though so I'll have to experiment.

Kevin Kuehn 12-18-2011 09:42 PM

Quote:

Originally Posted by bandersen (Post 3021655)
A little web searching pulled up this thread describing exactly the same problem and some solutions: http://www.antiqueradios.com/forums/...p?f=3&t=108670

Thanks for posting the ARF link. I hadn't read that one before, that was some very informative reading. Now if I could only remember all this stuff I read for more than a couple days, I could be like smarter :screwy:

bandersen 12-18-2011 10:54 PM

Yeah, lots of good info in that thread. I took a closer look at my scope snapshot and estimate the ringing frequency at roughly 180kHz just like Tom noted. I see what chokes I have on hand and try to cobble together something with that resonant frequency.

bandersen 12-21-2011 05:36 PM

I used the capture mode on my scope to analyze that ringing more closely and it's definitely around 180 kHz.

http://farm8.staticflickr.com/7168/6...5d9cf709f0.jpg

Here's a schematic of a later production run showing the damper filter and unknown inductor L406.
That mystery value might be revealed in Riders Vol #13, but those pages are missing from my copy :tears:
http://farm8.staticflickr.com/7155/6...2621531ded.jpg

Knowing that it's a 0.0068uF cap and 180kHz I pulled them into a resonance formula and got about 115uH. I rounded up to the next standard value - 120uH and ordered a few.

I hope it does the trick.
http://farm8.staticflickr.com/7157/6...0fc7337fe9.jpg

bandersen 12-21-2011 08:36 PM

Something else I'm working on is the washed out picture. At first I thought it might just be a worn out CRT, then I got a scope on the 6AC7 video output tube.
It turns out the signal on the grid is about 33% low and so is the output going to the pix tube. Now, I'm going through the IF stages hoping to boost the gain.

As with every Admiral I've worked on lately, most of the resistors are way off value. This 1K resistor is measuring almost double that.

http://farm8.staticflickr.com/7148/6...9f7bbea553.jpg


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