Admiral 19A15 restoration
 

Don't need any more TVs, but who could pass up a classic 7" 1949 Admiral in maple cabinet with spare 7JP4 and Sams photofact for $10.95 ?

Space CRT is RCA branded, dirty and most likely used, but if it has any life left, I'm happy.

I think I have a spare small brown knob but finding the correct brown channel knob will be a challenge.
The 7" sets used channel knobs with much longer shafts than the more common console versions.

Will pull out the chassis and test CRTs over the weekend.
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Wow… It even has a nice grill cloth...don’t see them like that too often...they always shrink on the sides! Score!

Bob, I couldn't agree more. Heck, you've been there before, as they say. Looks nice, thanks for the post.

I had some time to dive into the set and here's what I've discovered.

Overall the cabinet is in quite good condition in spite of the stains. I think I can dig up the correct knobs.
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Peering inside reveal a torn speaker and what appears to be a replacement CRT.
I say that because the shield is not correct and it's help in with a zip tie.
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Found a curious circuit drawn in the Sams. It looks the the HV supply was tinkered with.

Here's the underside. Yes, it was certainly worked on. Maybe in the 80s? Those are some nice looking 10kV Sprauge caps. Sure hope the are still good.

What's going on with the ceramic trimmer cap up top ?

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That's what. Someone has indeed replace the HV coil and re-engineered the driving circuit.
That multi-deck coil reminds me of the one Dumont used in the "Clifton"
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I did try powering it up and managed about 2.5kV by tweaking the cap. That's only about half of what it should be.

I'm leaning towards restoring the original circuit using a coil from a Motorola TS-18

Here the donor coil from a Motorola. The driving circuit is nearly identical in both schematics.
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Meanwhile, I started on the cabinet. I first thought I'd do a light sanding, clear coat with lacquer and call it done.
However, as I sanding the old finish it became apparent that the underlying veneer was in excellent condition. None of the stains or scuffs had gotten into the wood.

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I ended up sanding until all the defects were gone while retaining most of the grain filler.
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Then a few rounds of sanding sealer and light sanding. Thin coat of Mohawk Light Golden Oak toner lacquer and some clear gloss. Quite happy with the results.

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It's interesting they put channel decals below the channel number plate...it's like that joke about the golfer wearing 2 pairs of pants incase he gets a hole in one.

Nice job Bob. You can see that the gold channel numbers were hard to see against the light finish. Likely the upgrade to the plastic plate happened early in the run. Those are very good performers once restored.

Bob you are among other things, The Cabinet Whisperer. That looks awesome.

Thanks for the kind words. Now let's see if I can get the set working.

Here's a closeup of the HV supply area where the modifications had been done.
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I'm striping it down to the bare bones so I can restore the original configuration.
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The transplanted Moto coil fits perfectly.
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Even better, it seems to work. I have about 4.5 kV now and a raster :)
I can't get sharp focus or any reception so still plenty of work to do.
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Hard part's done.

Cleaning out some tin whiskers fixed the focus problem.

Was able to get an image by injecting into the IF using a B&K 1077B.

It behaves strangely though. Regardless of whether I inject before the 1st, 2nd or 3rd stage, I have to use the max output to get an image. If I back off just about 5% on the level, the screen blanks out.

I'm having to drive that IF really hard in other words or I get nothing. Figure it's something with the AGC. Will keep poking around.

I removed the tuner for better access to the components around it. Did a full recap and the set is working quite well now :)
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I had three 7 JP4s handy to try out in the set.

Both the CRT installed in the chassis and spare in the box worked fair but not great. They also tested poorly on my Sencore CR-70.

So I used the AUTO-RESTORE function on both and there was a noticeable improvement.

Surprising as I've never had luck restoring one before.
Here's an image taken in a moderately lit room. Before I had to dim the lights to watch the set.
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Now as for the third which came of a spare 19A11 chassis...
Well it tested with great emissions and life test but is the most worn out picture tube I've ever seen!

That really shattered any thoughts that a CR-70 can reliably test a 7JP4. I mean sure it can detect shorts or a dead or really weak run.
However, forget about assuming that strong emissions will produce a bright image.

AUTO-RESTORE did nothing except reduce the emissions very slightly.
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Burn baby burn. Either it has a ton of hours or there is some contamination in the vacuum to produce an ion burn.
I have not examined the getter yet to see if it is used up.

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Getter is completely used up in the dim 7JP4. I think a trace amount of air inside would account for the damaged phosphor and dim image while it seemingly has good emissions.

The air/gas will also increase the conductivity over that of a perfect vacuum increasing emission current and giving a falsely good emission reading....
I've never seen a gassy CRT that had emission and read as having weak emission... they are either stone dead or brand new, emission reading wise from the neon bulb effect.