Admiral 17T1: Never Give Up, Never Surrender

[Winky Dink]

Deja vu. It feels like I've been on this forum before.



I've had this Admiral 17T1 for 11 years, and I've had three previous episodes of trying to fix it. This is the fourth episode checking and rechecking the
electronics against four different schematics. Before last night, this was the best I could do:



Last night I got this. I touched no control except 'on' and 'off.'

Flickr link to video: https://flic.kr/p/2mycedY

Overnight I changed nothing, but this morning I got this:

Flickr link to video: https://flic.kr/p/2mzpadh

One question to start. So far I've been using a combination VCR/DVD with a coaxial cable and F connector for both tapes and disks. I want to use a DVD player. How do I get the signal from the player with RCA plugs and sockets into the TV?

Thanks for listening,
Winky
aka Little Radio Man.

[Notimetolooz]

You need to use a video modulator. Cables with RCA connectors go between the DVD player and the modulator. Then a cable with F connectors goes from the modulator to a 75 to 300 ohm balun transformer that converts to twinlead that connects to the TV terminals. I have a RCA modulator but I don't think those are available now.
https://www.amazon.com/GE-RF-Modulat...3960697&sr=8-2
You should get a modulator like this now, they put out a old NTSC analog signal.
At some point only the modulators that do digital will be available, those will not work with vintage TVs.
There may be something mis-wired on that TV. Do you have an oscilloscope?
Maybe the deflection frequencies are far off or badly distorted. Maybe the video detector is installed backwards. The sync separator might be fowled up. A scope could help sort it out. Have you checked the voltages in the deflection circuits?

[bandersen]

Notimetolooz beat me to it

[Winky Dink]

Thanks for the reply. My approach to electronic restorations is that if all the parts are good and you put them together in the right way, it will work. Beyond that, my understanding of electronics is minimal.

Sometime recently I came across someone making and selling modulators. Maybe it was the guy on Amazon. I'll follow up on that.

I'll look into the television sections you mentioned. What are you referring to as the video detector? When I hear "video detector" all I can think of is a tube--which even I can't install backwards.

As for oscilloscopes, I can't even spell it. Plus, in Idaho possession of an oscilloscope is a class B felony.

Thanks again,
Winky

[jr_tech]

Indeed, a cheap RCA modulator will work just fine.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

jr

[Tube TV]

That's an interesting picture. Your horizontal oscillator is 100 miles off from where it should be. There also appears to be a sync issue, and about 2/3 of your vertical is compressed into a band at the top.
The horizontal is either half, or double of the normal horizontal frequency in the first video.

Has the horizontal hold control slug been turned way to the bottom or the top?

Try adjusting the H hold control from one extreme to another.

Has the set been recapped?

What work has been done to it?

[jr_tech]

Does this schematic match your set fairly well ?

http://www.earlytelevision.org/pdf/a...1_telaides.pdf

jr

[Winky Dink]

I'll look into slug tonight.
The set has been thoroughly recapped.
I have four schematics. I settled with the Telaides schematic, which matches almost perfectly. The Admiral 19A1 and 17T1 had a number of production changes over time plus recommendations for dealer-installed upgrades. So all four are different.
I'll make a list of things I might have screwed up.
Always grateful for your patience and guidance.
Winky

[Notimetolooz]

The reason I asked about the oscilloscope is that many times if there is an image on the TV screen it sort of functions as a oscilloscope itself, but this image is so scrambled that it is tough for me to figure out. A scope would let you view the vertical scan, horizontal scan and video signal separately which may clarify what is going on.
I think there are several problems being seen at the same time, so it is confusing.
Some sets used a germanium diode for the video detector. If the set has been worked on it may have been installed backwards. That might invert the sweep sync pulses and confuse both vertical and horizontal scans. However the video signal doesn't seem to be negative so maybe the detector is not the problem.
Tubes, caps and resistors are not the only things that can cause problems.
Also if it has been re-capped, there could be mistakes made.
If you have been trying to get the set to work for some time, do you have links to what went on during those earlier attempts?

[Winky Dink]

I am looking through notes and photos going back to 2010,and I will shortly post the history with schematics. The short story is: I bought it and it worked. The chassis had some previous modern repairs, but also had failed soldered connections, a cardboard electrolytic with goop oozing out, and other stuff. I started "fixing" it and it broke.

[Winky Dink]

This is the saga of the Admiral 17T1. I bought for $100. Took it home, hooked up a VCR, and this is what I got:
Adm 17T12 010 by H Boyars, on Flickr

Click the pics for the original photo.

I opened the chassis and saw stuff that had to fixed. Like these open solder connections:

17T12 035 by H Boyars, on Flickr

And this cardboard electrolytic:

17T12 037 by H Boyars, on Flickr

The point is that it really needed electronic restoration, which I started two years later.
Two potential problems were (1) I was using an early 19A1 schematic, and (2) The only diagnotic equipment I had was a multimeter.

Making no progress, I resorted to testing components by replacing them. Someone suggested that C37 and C39 might be problematic. Unlikely that mica caps would fail, but I went ahead and replaced them. Unfortunately, I didn't notice that they were rated 1,000 volts, so I used 630 volt caps. Here's a schematic showing the offending condensers (in yellow):

Adm 17T12 8900 by H Boyars, on Flickr

Lo and behold, the instant I turned on the power some wire insulation melted, the wax on C41 melted, and the horizontal size pot was toast. I replaced the pot, wiring, and resistor and then put the set away for six years.

I started again last year with the Wallace-Telaides schematic, tube testers, a capacitor tester, and lots of other stuff. Tested every capacitor and resistor except micas, ceramic, and tiny dogbone resistors. Checked continuity throughout the set including the resistance of every coil. And ensured that I had a good set of tubes. Even tested the picture tube on a Philco 7053 CRT tester.

Replaced everything that needed replacing, then rechecked the wiring for every component. This is what it looks like today:

Adm 17T12 5020 by H Boyars, on Flickr

For Tube TV: I'm guessing that the horizontal hold control with the slug is the transformer on top of the chassis directly over the hhold pot. If so, the slug is centered and has no screwdriver slot for other-than-factory adjustments.

Phew, that was a lot of work. I hope the links work.
Winky

[Winky Dink]

One more thing. When I restarted the project last year my biggest concern was I had errors related to using a 19A1 schematic. My first step was to invent the "Schematic Differential Too." The Rider 19A1 schematic and the Telaides 17T1 were made on the same template. I printed the Rider schematic in red on white paper and the Telaides in black on transparency film. This is how I identified differences in the schematics:
(I just learned how to embed photos that you can click to go to the original)

Adm 17T12 5000 by H Boyars, on Flickr

Hence I wired the 17T1 to be in compliance with the Telaides schematic. Except for R41.
Thanks again.
Winky

[Notimetolooz]

Hummm, C41 is across some tube filaments, hard to see how the wax could melt and the filaments did not burn out unless it was a dead short.
That doesn't explain why the horizontal size pot burned.

Are you sure you read the value on C37 and C39 right?
They look a bit small for 1000 pf, 1000V.

What do you mean "factory adjustment"?
The coil may adjust with a hex tool (non-metallic).

[Electronic M]

If those mica caps were in the deflection stages then they are likely to have failed. Deflection circuits are much harder on micas than tuner and IF stages are. About a year ago I found a mica dead shorted in a 7" Philco electrostatic deflection TV's sweep.

[bandersen]

It looks like you used some sort of ceramic cap for C37 and C39 ? Unless those are C0G type dielectric that could cause problems.

I don't think the core of the horizontal transformer is adjustable.