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!":nono:)? Thanks!

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.

I now get a local FM radio stationThe 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

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 :)

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.

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.

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.

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.

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

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...

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

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?

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!

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

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

Dave, Thanks for the link- very informative. Up until now I've been scared of any alignment procedures, as a lot of the sources (on the internet) say best not to touch, as you may only make a working set non-functional. In this case, I have nothing audio to lose. I also have the same Heathkit signal generator and my DVOM has a frequency function I can check it against. My signal generator has no leads, so I built some using shielded audio cable and test lead clips (Radio Shack is still useful for something outside of cell phones!).

One thing I didn't quite understand. You mention the connection between the signal generator and the tube on the tuner (we have the same tuners), but you mention putting cardboard by the tube shield to prevent grounding. I couldn't see how exactly you did this. Can you describe it? Bear in mind I'm a newbie here...

Thanks!

You just want the tube shield not to be grounded, if you can keep it up a bit from the chassis, that is good, I think I used the cardboard to keep a strip of metal from touching the tube shield. The goal is to couple the signal thru the glass of the osc tube, the shield therefore must not come into contact with the chassis which would ground out the signal.

The hardest part of working IF for me is correct termination and cabling from gens to test equipment. You want short leads, and correct termination blocks (at least when looking at band pass from sweep gens).

I think the tuner may have a defined test point that may work better than the tube shield, check the riders. I do think its not as critical when just doing a single freq peak (unlike the sweep gen and scope when you are trying to analyse a trace).

and using the long fibreglass rod helps, just moving around the set can damp out signals and change tuning, you notice that as I peak up the last coil near the tuner.

A turn or two of hookup wire wrapped around the mixer tube, taped securely, is a good method of injection in lieu of the ungrounded tube shield, which may be prone to over-coupling.

An update. I remembered that when I was working with this set a few years ago, I would get a better audio response from a VCR rather than a DTV converter. I connected up the VCR and with the contrast control all the way up, I could hear faint audio under the interference. Since the chassis is in the cabinet, I did a rough "ear alignment" (as Phil calls it) and was able to get a sizable increase in volume. (I only adjusted the top two coils, as the third is accessed from the bottom. I will adjust this one as well when I pull the chassis back out for the formal instrumented alignment) The first IF coil has a silver mica cap in it, while the second uses a tubular ceramic.

This reminded me of a quandry I was dealing with back then: If I used a DTV converter, I'd get a nice picture, but no sound. (Even with the contrast turned all the way up, which functions more as a gain control in this set, the sound is absent or very faint. The contrast is set around the middle of the range to get a good picture with no distortion or retrace lines.) If I used a VCR, the sound signal is stronger, but with the contrast dial turned to a point where the audio is a decent listening volume, the video is overdriven and distorted. I wish I could get the good video of the DTV, but the sound of the VCR... Any ideas as to what else I should be looking for? (Yes, I have the sound control on the DTV converter box turned up to the max) I also want to put a signal directly through the amplifier in the lower chassis and verify that nothing has weakened in the main amp itself.

Blonder Tonge AM60 modulator, far better than anything coming out of a VCR or converter box

Blonder Tongue AM60 modulator, far better than anything coming out of a VCR or converter box

Are there any other modulators out there that work well? I looked at the AM60, but it's kinda pricey...

Many of the B-T agile modulators listed on eBay are overpriced, but if you're patient, it should be possible to find a more reasonable one. I got one for $26 + shipping.

I just did a quick search and there's one listed with a current high bid of 99 cents. Another with a BIN price of $39.95.

Regarding digital TV converter boxes, on mine the audio is just plain weak. I got a little more by switching it from stereo to mono, but not much. Perhaps others are not like that . . . I only own one.

Phil Nelson

If I can get a BT mod delivered for under 50$ I consider it a good deal. With a properly (home) made antenna they are worth every cent of that price IMHO.

Thanks for the tip, Phil. I was looking at the B-T website, where they sell for a grand!

Are there any particular features I should look for?

Well, I finally had the time to pull the chassis back out and go through the process of peaking up the sound IF stages. The sound is so much stronger now! I can even use my DTV converter and get plenty of volume, even with low contrast. Thanks to all for pointing me in the right direction and the links to the how-to videos. This was the first TV I've ever done and it has been (and still is) quite a learning experience.

One odd thing I noticed: when peaking the upper coil in the first stage, I would approach the peak and just before getting it there is a sudden drop off. When I turn a bit beyond it, the voltage comes back and I get the sweet spot. What could be causing this? I turned the core back and forth and I hit this drop off every time...