I too prefer the ota, seems more enjoyable using the BT. After trying to troubleshoot frustrating tuner problems though, it's kind of enjoyable to be able to use your project a little bit. Also, in trying to stabilize/set the sync circuits, I found they were working properly, but the tuner was causing what appeared to be sync problems. Helped me to narrow down the problem.

oh yea, I do the inject method all the time. on my consoles with stereo amps I will bypass the tuner so I can feed in L&R audio for true stereo (reversible to tuner audio).

I must not have read the post about the audio in very carefully
Thanks for the pointer. I'd like to hear some audio as a reference.

I wouldn't be able to sleep at night knowing the tuner section didn't work either. It would be like restoring a vintage car and leaving the doors off. It would still drive right? Butt ugly though

I realize how much of a challenge it could be to get the tuner section dialed in, especially for a beginner like me. I also want to get a BT so I have more options. I don't really like messing with a DVD player either, especially when I can stream from my computer and create my own programming.

your close, the tuner is pretty broadly tuned. If its not working its going to be something simple I would imagine. the main thing is to avoid adjusting any tuned slugs.

Just remember, sometimes less is more when it comes to replacing parts, unless something is wide open or shorted there is a good chance it will be fine. I was working on a crosley a while back, a cathode resistor in the IF was 250% off, guess what the pic is great with no issues what so ever. If you see gold banded ORIGINAL resistors then its prob critical if no tol given then don't worry about it. The only place I have had some issues with resistor that were like 50% out was in some multivibrator sweep circuits, even then the prob was not that it did not work it just did not have enough sweep.

That's pretty amazing to me that a resistor can be so far off and it would still work.
I've only been doing this for a few years and I always thought electronics--especially TVs had to be precise. My next set I'm going to take your advise and just get the electrolytics and wax caps replaced and then fire it up. I'm working too hard. I guess it's that fear that I could wreck something. That's the other thing--these sets are tougher than I thought.

I haven't messed with the tuning slugs. On a simple radio restore I'll align by ear sometimes but that's only a few IFs tweaks.

Too bad just radios isn't shipping this week. Every time I look at the last pic of the CRT I get a little impatient because it looks close.

So Dave, did you do this for a living?

actually I am a bean counter by trade, this is just to forget office work for awhile...

Tube circuits often seem to be very forgiving except if there is an RC network, where time constants are involved. Voltage divider circuits can also be somewhat of an issue if one side drifts a lot more than the other, and the other place where things get funky are in the sync separator where voltages are important for the tube bias to be correct for cutting off the video info to get just the sync stuff.

Things like screens,bypass, plate load and grid leak are generally not too critical. Tubes can vary a lot in performance from new to very old, so they are a much larger variables than a resistor, yet you will find that tubes that test very weak often work just fine. Caps are another area that can very widely in value in some circuits and be fine, but again in tuned circuits not so, and that is why the micas come into play. there is also things like AGC that compensate for gain issues that may be a result of weak tubes or resistor issues, so the set can operate in a very large range of issues. What TV's really don't like are gassy or grid emissions in the tubes I think a good emission tester with a good gas/Grid emission test is prob more important than a high end GM tester. Your best bet is to just have a few good tubes laying around to sub, esp the HV tubes (HOT/HV rec/Damper).

I can't totally agree on that, and, I have two tv's to prove it.
RCA 6T74, and, the 16" round Admiral...
There are a number of resistors not crittical. Sure. That would include audio, tuner, I F 's.
However , sync, horiz., and, vertical circuits more crittical.
Also, don't forget one thing..
Alot of the cheaper carbon resistors tend to drift while playing. Especially if they are 1 watt, or, more.
But, I've even had cheap half watt reistors go nuts on me.
Radios don't tend to be as crittical.
TV circuits need to be a little more precise. Sure.. A munber of circuits did use 10-20 percent resistors.
The problem is alot of them go either alot higher, or, alot lower than that.
Yah. I even ran into them alot lower on the Admiral.
The point to know is which ones are more crittical than others. You don't usually need to replace every resistor in the set..
Yes, tubes are more forgiving, but, not all circuits are.
On the horizontal output if there is a 100 ohm cathode bypass resistor, and, it has gone to 150 ohm, or, more, you can lose your hv.
The tube goes into thermal runaway from drawing too much current.
Result:
Tube dammage, and, can dammage flyback.
You need a good meter to check them.
Oh. And, by the way.
First. A number of resistors will check alot different in circuit than they will with one end disconnected.
Next. I find that if your digital meter goes nuts, and, the resistor in question shows a wide range of resistances, it's time to replace it....

In my Admiral, I had two such resistors in the video circuit, and, it made the voltage go crazy, and, tube nearly went into cut off...
Bill Cahill

2 comments:
1- I can empathize with you re Capacitors - I have an order pending at Just Radios too:-)
2- You mention alignment - that is one area that needs to be addressed in the TV collector community. I've never dabbled with aligning one of these TVs and would love to learn.
I have the test gear to do alignments but lack the knowledge. I'm looking for a
cheap 1950's TV with a small CRT to use a my victim:-)
There is talk that at next years ETV Convention that they are going to host classes on
TV alignment. That would be great.

Carl

Alot of the cheaper carbon resistors tend to drift while playing. Especially if they are 1 watt, or, more.

This is a good point Bill. I've noticed even new resistors can change value after heat from a soldering iron is applied. I always check resistors before I install them to make sure they're right. On a whim I checked one after I installed one of the legs so it was still out of circuit, and it had drifted up a little--I'm guessing from the heat of the iron. I didn't check it after it cooled but I'm guessing it went back down.

The hardest part for me is knowing what is critical and what is not simply because I'm new at this. The last thing I want to do is destroy the flyback because I didn't replace a 10 cent resistor. I can also see the point of a lot of the other guys here where it's unnecesary and sometimes destructive to just go in and start replacing everything--especially if you don't have a baseline.

It sound's like the conservative thing to do is get the set running with the important caps replaced and the few critical resistors replaced and then go through and check voltages etc.

What I'm hearing is the the Horiz circuits are important and they take a big share of the stress.
So much to learn here and I appreciate the help.

Carl, I'm having a hard time finding info about Vintage TV circuits let alone alignments online in general. That tells me there are not many people doing it. What is the ETV convention?

http://www.earlytelevision.org/

Phil Nelson

You should check the current in the cathode circuit of the HOT that will give you a good idea if everything is ok, generally the current is given On your set there is prob a HOT fuse that should protect you from any issues (make sure its the correct fuse).

Like I said before, RC circuits and voltage dividers and sync sep are the critical ones, If you study up on some old TV books you will begin to see where they are.

Yes there is a fuse and it's correct. It's usually one of the things I check since people will put whatever they have in if they don't have the right one.

Wish I had the resources to make it to a convention like that. That's a great site and I just found a link to a video stream of this year's convention--looks like I get to go after all

I seem to remember them getting all of Hawkeye's CRT rebuild gear--did anything come of that?

Found the info

http://www.earlytelevision.org/crt_proj ... l#may_2012

I finally got the silver micas and replaced them one by one. Here's a video I posted on YouTube. You'll notice around the last 15 seconds I stabilized the vert hold. Getting closer. Any suggestions?

http://youtu.be/7DEmD1wLZWg

I also forgot to mention I have the audio working loud and clear
Tomorrow morning I'll measure voltages.

You did adjust the Horizontal Hold through its entire range?
Looks like the Horizontal Oscillator frequency is the issue.
S/b get a steady signal at 15,734 Hz. Look closely at the
capacitors and resistors around the Horizontal Oscillator.

Carl

Started with the Horiz output tube, 6BG6. Voltage on pins 3 and 8 were spot on but pin 5 showed just a fraction of a negative mv. It should be -7v. I replaced R77 and now it shows -6 only when I rotate the horiz drive pot all the way to one side. R5 and R76 are my other suspects. Am I on the right track?
All of the caps in that circuit have been changed.

As I get a chance I'm going to be going over all the voltages in the Horiz circuits.

Carl, I did adjust everything carefully for the best picture and it still would not stabilize. I even carefully adjusted the horiz freq pot for the most stable pic. After I got the best picture I could, it still began drifting after a few minutes. Is that due to resistors heating up or something else?

Do you have an Oscilloscope that you measure the Horizontal Oscillator
frequency?

Carl