Amazing how much damage one bad cap can do
 

I recently a posting on craigslist fro a free 1953 Admiral TV chassis just a few miles form home so I went to check it out. It turned out to be a 30B1 from 1948/49 with a replacement under warranty CRT from 1956. his parent bought the set new and he aid ti was working into the 90s when a transformer blew.

Unfortunately, he kept the nice blonde cabinet it came from to install a flatscreen inside. I figured if I get it running, I can offer it back to him or maybe put into one of my unrestored sets.

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Ouch!
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They stuck with Admiral branded tubes as the logo changed over the years.
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Big gobs of wax under the power transformers seemed to confirm the previous owners prognosis but I want to find out for sure.
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I also noticed a fried power resistor and another that was open. I decided to replace them and try a controlled power up.
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No luck - the power switch is fried. I jumpered it and tried again. At about 80 VAC the replacement resistor was getting quite hot so I turned it off and did more hunting.

Eventually, I found another charred resistor in series with a 0.1mfd bumblebee cap. I measured the cap and it's a dead short!
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It's also split open. So that one cap took out several resistors and the power switch :thumbsdn:
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Ah, that's better :yes:
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It still needs more work but has a pretty good picture already.
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You sure know your stuff on these things. I've been pushing my internet bandwidth watching your Predicta "Holiday" restoration vids on Y-tube (I'm getting ready to replace some components on a Holiday chassis).

When I was young we had an old '50s Admiral ('52-'55?) that lasted until around 1969. It would be great to see the one you're working on get re-installed back in its original cabinet.

I hope to finish off the Holiday cabinet restoration very soon. I have my refinishing supplies out and am working on several cabinets before the weather starts turning cooler.

This chassis came from a 30B16 set that looked like this only with a blonde finish.
http://www.shedradios.com/sitebuilde...16-463x600.jpg

If he doesn't want it back, I think I'll put it into my similar 30A16.
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Here's a look at the repaired speaker. I was able to glue the original cone back together except for one missing section that I patched with a coffee filter.
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In spite of the cap incident, it's amazing how reliable those Admirals are while still utilizing so many original components after all these years. Possibly most of the caps are still good because that family kept using the set regularly up until if failed in the 90's. Pretty amazing. Very nice job gluing that speaker cone.

Very nice find, and it is good to hear that the transformers are not bad after all.

That CRT is from only a few blocks away from the rebuilder my employer used to use in the early 1980s, which was also on 47th Street in Chicago.

Nice job Bob! I agree, those Admirals are very cool with their "chunky" looking cabinets. The next best thing to the bakelite version! One day I will find a good one of those!

Admiral must've had a factory service agency like RCA service company.
The original owner always had the set serviced by them.
Admiral had their own distribution and parts division. They didn't use privately owned distributors like the other major manufacturers did.
Magnavox and Curtis Mathis did as well. No middle-man, meant more profit for the dealer and the manufacturer. :yes:

A little late Bob, but from me too, "Nice Job!". Good to see that vintage set working. The 26R12 that I bought several years ago was working too. But it got the same things done that you do, caps, caps and more caps. All of the major components were good except the CRT. But I got an NOS one for it.

Cheers!

We need a wider angle shot of that room :yes:

So it worked, with all of the other old caps still in place. Interesting.

Sometimes those old Admirals will surprise you. I have a Model CH21UH33 from '59 that's still working perfectly on all its original components except for one tube which needed to be replaced when I got it. This set also saw regular use by the original owners until shortly before I got it though, so the fact it didn't sit unused for a long period of time is a factor, I'm sure.

That photo was taken a few years ago and sets are now scattered around all over. I really need a place with at least twice the sq footage :yes:

I'd guess about half of the original paper caps had been replaced in the past. So they're old, but not quite original. All the electrolytics were though.

I had some height an linearity issues that were solved by replacing the electrolytic cathode bypass cap.

The sound is still really weak. Possibly due to leaky mica caps inside the IF cans or bad electros in the audio amp.

i had an admiral 12" bakelite console , i think it was chassis 20x1 , it ran on the original electrolytics and almost ran on wax paper caps , person i sold it to i told him to try to run it atleast once a month for an hour to keep the electrolytics ok , don't know if he followed my advice , i should have done the electrolytics to be sure but that was back in the days when i'd only replace electrolytics that were bad , now i don't bother i just do them all to save future headaches , i may have had one that i didn't do them all and faced a problem , i know a friend got one that was restored a 9-t-246 that had a vertical issue , while running it testing voltages the picture started to go darker and darker till it went black and i scratched my head and wondered what happened , i checked the cans and one was hot , that was the cause , this set was used a lot about 10 years previous but sat unused for a long time , perhaps the one who restored it reformed the electros or they were good enough when restored but that one went sour after siting for a long period of time.

mike

I ended up doing a full recap and alignment on the set. Bandwidth is great ( > 4.0 MHz) and the linearity is pretty good.
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One nagging issue is "waviness" in the picture. I cranked up the contrast to really illustrate the problem. I'm thinking there may be some horizontal ringing working it's way into the video ?
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Wouldn't that be closer to vertical ringing? Looks a lot like 60hz modulating the horizontal oscillator.

Well the picture is in sync so I'm thinking that it's something leaking into the video.

Just checked the service info and it says vertical lines or "wrinkles" on the left side can be caused by spurious oscillations in the HOT, yoke or horizontal drive settings. I guess I'll start there.

Barkhausen oscillation? Perhaps try holding a strong magnet close to the horizontal output tube to see if the pattern changes. Just a WAG, I have never observed BO.

jr

Swapping out tubes and the drive controls had little if any effect. What did help a bit has to adjust the horizontal oscillator coil on the back. The problem isn't entirely gone now, but it's greatly reduced.

Was the waviness noticeable before the total recap?

No, I don't recall it being an issue, but the set did have others problems like poor linearity. Seems like fixing some problems caused others :scratch2:

Here's where I'm currently at. With careful adjustments I can reduce the waviness to just a bright band on the leftmost edge. I think that's good enough for now. I'm going to pop it in a cabinet and let it run for a while and see how it goes.

P.S. There's no keystoning - I just had the camera at an odd angle.
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Yes he does and its good seeing people HAVE THE WILL to make it work again :)


GOOD FOR YOU MY FRIEND :)

those wavy lines are the same ones I was getting on my Dumont ra-109 , what made them go away was when I adjusted the width and drive and all that , they may or may not still be slightly there , I know when they were there tuning would make them lighter or bolder , I hadn't noticed them lately so when I run it again I will look closely and if they are there even faintly I will report it.

mike

Thanks! Once I get going on a set, I'm pretty tenacious. Especially with these Admirals now that I have some experience with them.


Adjusting the width and drive did help. The lines vary a lot depend on the programming. It's especially bad in dim scenes.



I put the chassis into my blonde 30A16 Admiral cabinet and retired the unrestored green cadmium monster that had been in there to the attic.
The sound really surprised me. It was much louder with my cable hookup than on the workbench.
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All was well for about 45 minutes then the vertical went haywire :sigh:
I guess I'll be pulling it back out sooner than later. Oh the joys of running vintage sets :)
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Looks like the vertical lin needed some tweaking, I suppose there's some more caps that need replacing in that circuit.

It might be interesting to put the original caps back in the horizontal oscillator and output section. Sometimes I wonder if our modern caps don't shield these circuits properly from outside interference. One end of the old paper caps were marked with the outside foil shield. That end typically went towards the lower potential voltage source.

I believe that I observed it in my Hallicrafters T-67:

http://www.antiqueradio.org/art/hallit-6708.jpg

The interference is seen as squiggly vertical lines running down through the reporter's face. It disappeared after I replaced the 6BG6T horizontal output tube, just as suggested in an old service book. The book noted that Barkhausen's is more prominent with weak signals than strong ones.

Another solution is to place a small circular magnet around the tube. The DuMont RA-103 has a little magnet mounted inside the HV cage to suppress Barkhausen's.

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

The set has been fully recapped, but I used the cheap generic yellow caps. I wonder if one failed ?

I suppose I could dig them out of the trash. I've heard there are tricks for determining the outer layer in modern caps using an RF generator and oscilloscope. I think the idea is to put the probe tip against the body of the cap, apply RF to either end and observe the signal strength on the scope. The stronger end will be the outer layer.

I swapped out several 6BG6s and it had zero effect so I think the problem lies elsewhere. My suspicion is the mica cap inside the yoke across the horizontal windings. It's not so easy to get at though.

Probably not....... Almost nothing is made as good as it was :(

Of course, when I pulled the chassis out and powered it up on the workbench it worked just fine :rolleyes: I'll poke around with it for a while then stick it back in the cabinet. Grr!

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Cool! Godzilla! what Chicago TV station is that? Is that Svengoolie?

It's Antenna TV (9.2 in Chicago). Svengoolie is on MeTV Saturday nights.

I just have to add this in regards to MeTV. I am so glad that this channel exists over the air! At first I tuned in periodically on my bedroom's early 80s Panasonic, but now I am starting to prefer that ONE channel to all 200 or so of the DirecTV that is up to about $80 a month. Not long ago I was aggravated as late at night I couldn't find a thing on DirecTV, so I unplugged it and moved a digital converter into the living room and was fine the rest of the night.

Nearly any time of the day or night something worth watching is on except Saturday morning when they give in to the most awful kids programming and cartoons I have ever seen. Really weird stuff that I couldn't imagine being interested in if I were a kid, but times change I guess. With their format one would think that they would be showing the decent cartoons of yesteryear. I'm sure kids would catch on and probably enjoy the old cartoons from the 50s-70s.

As a footnote, sometimes hours of the various versions of Lassie get a little old. I never realized that there were at least three different versions. I believe the original was Jeff's Collie, followed by Lassie with Jeff (the kid) and a couple of different moms (June Lockhart and Chloris Leachman), and finally the 60s-early 70s version without a real "sitcom" format just showing the dog on adventures with his owner who is something like a forest ranger. I think I am watching too much TV! Thank God they aren't showing blocks of Emergency!