Back after a long hiatus... Admiral Tuner Help Needed - Videokarma.org TV - Video

UberVacTuber · #1 01-02-2015, 04:12 PM

Hi all, after a long hiatus on projects after welcoming my first child into the world, I've finally had a little time to once again do battle with my Admiral 30A1 TV. It uses the A-1582 Tuner assembly. This TV has been fun, and the picture issues were all sorted and for a short time it was working OK. It had a good picture, but the sound was a bit on the weak side- you could barely lock it in with the fine tuning control. This gradually worsened to the point where you couldn't pick up any sound at all- just some buzzing. I checked the audio IF section and the tubes in that portion, but nothing helped.

I took a look at the tuner (since it still has all of the original parts) with the original intention of rebuilding it. However, after seeing that there was no way to remove the rotary switch assembly from the chassis in order to get at 90% of the guts tucked away in there, I just redid the few caps and resistor under the FM Trap coil, where the audio and video signal is delivered to the Audio and Video IF's. These had all drifted beyond their rated values.

Here is where things went downhill. I put the tuner back in and tested the TV. No sound, no video. After re-checking things, I discovered that I had misconnected the filament voltage feed. Hoping that was the issue, I reconnected it on the correct terminal and tried the set again. I still don't get a picture, and I now get a local FM radio station out of the speaker- RATS!

So, I have been looking for a resistance chart for this particular tuner to see if I can find where I messed something up. My Riders and Sams manuals only cover the most common tuner for that model (94C9-2). I'm hoping it's a matter of knocking the tuner out of alignment with the new components, but knowing my luck I probably screwed something up.

Sorry for the long post. Anybody have some insight as to what to look for (aside from "If it ain't broke don't mess with it!"

)? Thanks!

Jon A. · #2 01-02-2015, 07:59 PM

Quote:

Originally Posted by UberVacTuber

Hi all, after a long hiatus on projects after welcoming my first child into the world, I've finally had a little time to once again do battle with my Admiral 30A1 TV.

Hey, congrats!

Sorry mate, I don't have any info on the tuner. I'm sure some here will.

Phil Nelson · #3 01-03-2015, 12:47 AM

Quote:

Originally Posted by UberVacTuber

I now get a local FM radio station

The FM radio band is sandwiched into the frequency space between VHF channels 6 and 7, so this may not be as nutso as you think, especially if your TV happens to be tuned to channel 6. The frequency band for channel 6 ends right below the space where FM radio begins.

I guess you have recapped this TV.

Did you ever clean all of the tube pins and sockets? If not, wiggling tubes sometimes magically cures problems by restoring contact between dirty tube pins and socket holes, although cleaning is obviously preferable to trusting in the random wiggle.

Did you ever adjust the individual channel oscillators (page 3-40 of Riders)?

Did you ever try to work through the audio alignment procedure?

Did you ever clean the contacts in the tuner?

How hard would it be to reinstall the original tuner parts that you replaced?

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

Dude111 · #4 01-03-2015, 07:10 AM

Quote:

Originally Posted by UberVacTuber

Hi all, after a long hiatus on projects after welcoming my first child into the world....

Ahhhhhhhh god bless you and the little one!!

Welcome back my friend......Good luck with this tuner

UberVacTuber · #5 01-03-2015, 07:36 AM

Thanks, guys. Phil, you've forgotten me... :-) it's Dan Jones. You and I e-mailed each other a lot when I was getting this set back on its feet. Good to hear from you.

I read in the manual about FM interference and how it can relate to those channels. However this is on channel 3. Anyway to answer your questions:

-The set has been completely recapped (with the exception of most of the tuner), and pretty much re-resistored. The resistances in the rest of the set were in spec.
-I cleaned all of the tube sockets with DeOxIt.
-I haven't messed with any of the channels as I only need channel 3 in order to use a DTV converter or VCR/DVD as there are no more analog broadcasts, and it has been working fine.
-I've never attempted an alignment before. That is something that I'd likely need some handholding on the first time I try it. Plus, I'm limited in what gear I have to do that kind of procedure...
-The tuner contacts were also cleaned with DeOxIt cleaner and contact restorer.
-It will be pretty hard to reinstall the old parts (one resistor broke apart...).

The video signal quality has always been great.

DaveWM · #6 01-03-2015, 01:49 PM

pretty sure Bob Anderson ran into sound issues like this, turned out to be the audio IF suffering from silver mica migration on the integral caps.

the way to know would be to see how well it responds to audio IF alignment, if the slugs do not tune up sharply then there is your prob. I am no suggesting a shot gun approach as I prefer to diagnose and correct, but if you do have issues in the audio alignment, dont forget those caps.

Electronic M · #7 01-03-2015, 01:55 PM

If you have cable TV that still offers analog (it does still exist, and I have it), then you may want to hook that set up and see if any position of the tuner gets anything. It may be a good idea for you to get an agile modulator so you can try different channels and see if any position of the tuner can get say channel 10 out of a modulator.

If you can get reception on a different channel with a capable signal source then it may be wise to not mess with it further, and simply use it with a signal it likes.

UberVacTuber · #8 01-03-2015, 02:24 PM

Interesting that you mention "silver mica disease". When the set warms up, a few seconds before the picture comes up, a loud screeching noise briefly cuts across the audio. Early on, I don't remember it doing this. I'm hoping Bandersen will chime in here as he's got the same model.

If I get time tonight I'm going to double check my work. If I goofed on the connections between the tuner assembly and the main chassis, I could have miswired something else. It's a pain to remove, but I don't have much choice.

Phil Nelson · #9 01-03-2015, 03:23 PM

This article has a section about replacing mica caps inside audio IF cans, if you're curious about that:

http://antiqueradio.org/Admiral24C15Television.htm

Since you lost both picture and audio, I wouldn't monkey with those cans yet.

It's possible that you have more than one problem:

1. Whatever caused weak audio in the first place. (Maybe your audio just needs alignment, or perhaps the mica caps need replacement.)

2. Whatever led to the loss of both picture and sound.

Before opening up those cans, I would definitely double-check your recent work (#2), since that's when the picture+audio problem arose, and you had a good picture before.

As Dave suggested, it may be wise to try some diagnosis before shotgunning more components. For instance, if you have been using channel 3, you can at least switch your source to channel 4 and compare the results.

Phil Nelson

UberVacTuber · #10 01-03-2015, 03:28 PM

Agreed, I'd rather solve this issue and at least try to get back to where I was before looking into other issues. If I throw more variables into the mix, I'll really drive myself crazy.

I'll report back what I find...

bandersen · #11 01-03-2015, 04:43 PM

I've restored a few 30A1 series Admirals, but none with this tuner. There are mica caps inside the side IF cans that are prone to failure. If you do pop them open and replace these caps, it will require a sound alignment.

Here's one of them: https://flic.kr/p/ev9cu4

UberVacTuber · #12 01-03-2015, 04:52 PM

Well, I re-checked my work and I couldn't find anything miswired. However, I have a question: the caps I replaced were all mica units (the dipped ones with the little paint stripes to indicate their values). The ones I replaced were 1500pF, and I don't have micas at that value, so I used polypropylene film caps. I thought I remembered reading something a long time ago that said while capacitances may be the same, mica capacitors behave differently. Is there any truth to this?

UberVacTuber · #13 01-03-2015, 06:41 PM

Eureka! After reading more on how silver mica caps are preferred for RF signals, I took Phil's suggestion and put the original siler micas back in the tuner. Now I'm back to where I started. I'll read through the audio IF alignment procedure and see if it helps. If not, looks like I'll be looking at the micas in the IF transformers. I'll let you guys know what I find out. Thanks!

Phil Nelson · #14 01-03-2015, 07:57 PM

It's worth looking at the audio alignment. This TV has a "split sound" audio system, meaning that the audio signal is picked off quite early and the audio goes through its own sequence of IF amplification. The video signal undergoes a separate IF amplification sequence.

In some cases, where you have a fine picture but weak audio, the audio IF stages have simply drifted out of alignment with the video, so that you don't get the best audio at the same fine-tuning position as the best picture. Sometimes you can adjust the TV's fine tuner so that it gives the best picture, and then tweak the audio adjusters to improve the audio at that setting.

Phil Nelson

DaveWM · #15 01-03-2015, 10:19 PM

I had weak audio on mine, did an audio alignment helped a lot. One thing to watch out for is the SAM may show the wrong coil right off the tuner, there is a top and a bottom adj, the SAM on mine was different from the Riders, the Riders was right.

https://www.youtube.com/watch?v=fxayNcxB4Xs