Admiral 14R12 Restoration

[Phil Nelson]

If you have a source with separate audio and video (not RF) output, you can temporarily connect that video source to the video input of your TV. Typically, this is a spot directly after the video detector, where it sends the video signal to the grid of the video amplifier tube. This diagram is for a different TV, but it should give you the general idea:

http://antiqueradio.org/art/A-V_Adap...oInjection.jpg

If the picture looks dramatically better when you inject the video, that suggests that you have a problem somewhere upstream of the injection point, in the tuner/IF/detector stages.

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

[Crist Rigott]

Phil,
Thanks! I made the box and used alligator clips. I pulled the cap off the volume pot and clipped on the audio. Then I had a spare 6AU6 tube so I bent #1 pin up and soldered on a small extension. I inserted the tube and clipped on the video.

I have both audio and video now. I'll trouble shoot the IF stages now.

[Crist Rigott]

I have a question about my problem. It is either in the IF stages or the tuner. Is there a way to substitute the tuner? That way I could really narrow down the problem.

[Phil Nelson]

I'd look at the IF stages first. Tuners are comparatively bulletproof in my (limited) experience. Make sure the tuner tubes are good and its contacts are clean.

Yes, there are ways to substitute for the tuner. Back in the day, they sold "tuner subbers," little gizmos that do what they sound like. You can also inject an IF signal (and do many other tricks) with a BK 1077 TV Analyst like this one:

http://antiqueradio.org/BK1077BTelevisionAnalyst.htm

You can also make simpler measurements such as checking the gain of each stage, checking voltages on each tube, etc. If you have a voltage chart, that's one easy way to start.

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

[Crist Rigott]

Phil,
Thanks for the suggestions. I forgot about the voltage chart. I'll do the resistance checks first then the voltage checks.

[Crist Rigott]

Success! I did the resistance checks per the chart in Sams and found V5 pins 5 and 6 showed open when they should have had 2.6K to pin 8 of the LV rectifier tube (120V). I checked the schematic and R29, a 1K resistor, was between the tube pins and 120V bus. I then did a visual on the resistor and it looked good. I then bumped it with my finger and a lead pulled out of the resistor! I replaced the resistor and now I have very good audio and video through the antenna terminals.

I have to finish replacing the rest of the resistors and a few micas yet. But getting a good picture and sound is very encouraging.

BTW, the CRT, a 14CP4 tested very low on my BK 467 but played in my AMC TV came up real good with a very good life test when I gave it to my friend who has a Beltron. He rejuvenated the CRT for me.

[old_coot88]

Nice bit of troubleshooting! I stand in awe at the quality of your overall workmanship sir.