Admiral 14R12 Restoration

[Crist Rigott]

I decided to power it up again to check my progress so far. The good news is that it powered up nicely and my B+ is 244 volts. Sams lists 238 volts. I also have a raster and each control seems to do something. Like Brightness does control the brightness and so on. I only have a low level buzz coming through the speaker which can be varied with the volume control. Also no video.

I tried wiggling each tube but that didn't help. On a few like the sound IF amp it clicked pretty loud in the speaker. Seeing I haven't gotten to the IF stages yet, I'm not surprised.

What's left to do is the 3 IF stages, Video Detector, a little in the Video Amp, Sound IF amp, Ratio Detector, Sync Amp-Sync Separator, and the Sync Clipper.

Once these are done then I'll have to get into the troubleshooting phase. So far so good.

[Crist Rigott]

I recapped the Video Amp, Sync Amp-Sync Sep., and Sync Clipper. I powered it up and still no audio except some hash which goes to a loud buzz when I touch the center wiper on the volume pot. Basically the same thing as before. I'm thinking that the trouble lies in the IF stages or tuner.

BTW, the tuner inserts have numbers on them that seem to correspond to channel numbers. Does the ones with "4F" on them equal channel 4? I need to know so I can be sure I'm on channel 4 because my CD player and RF modulator are set to Channel 4.

Another thing, I remember seeing something about hooking up a CD player directly to the video section? thus bypassing the tuner. Can this be done?

Recapping that's left are the 3 IF stages, Sound IF Amp, and the Ratio Detector.

Thanks.

[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.