Problems diagnosing TV

What's the brand and model? Is this by chance a GE/RCA/Proscan? If so then resolder the tuner shield grounds. Otherwise, look elsewhere for cracked solder joints. Don't use it again until you fix it, further damage is likely.

Solder joints on any particular component, though?

Looks like it's an RCA F20631SE.

I think I just got a mild static shock turning the thing around with my hand near the RCA plugs. I might've gotten the shock off a teddy bear that's there, but I think it was the TV. Hrm.

Mike

Please disregard the earlier message. I'll try a fix this weekend, but it sure looks like you nailed it right off the cuff. As weird as the symptoms are, this seems to match up perfectly with the tuner shield ground failure:

James, you're a scholar and a gentleman. Thank you.

Mike

I'd like to start a side discussion on this.

Many years ago I briefly attended RCA Institutes in New York. I had a mild argument with one of the instructors, taking the position that theory was the most-important thing, that a good tech should have a sound understanding of electronics. (RCA taught many subjects at a college level.) He, on the other hand, averred that technicians should learn and work by rote.

40 years have not changed my views on this matter. But it is true that any good technician knows hundreds of things he learned only by practical, real-world, day-to-day experience, stuff that didn't come out of a book. One of the reasons I like reading the threads in this group is adding to my repository of such information.

I'm coming to a point, so hang on.

When I see the OP's symptoms -- which pointed to vertical sync problems -- resolved by fixing a cracked solder joint on the tuner shield -- I can only wonder in amazement. How did anyone ever figure that out? Or was it a case of a part-by-part visual examination of the entire set when nothing else worked? Broadly speaking... how does anyone go about "rationally" analyzing such problems?

When I was a kid, I read "Mac's Service Shop" and similar short stories in Popular Electronics and Popular Science. Back then, intractable problems were called "tough dogs". Given the greatly increased complexity of modern electronics, they're more like "rabid wolves".

PS: One of my high school friends was very much against "book learning". We were trying to repair a TV in electronics shop at around the time I was working through Milton S. Kiver's "Television Simplified". I had just read the chapter on sync, and had a good idea which component was defective. My friend was rather surprised when that component turned out to be the bad one.

The advantage of "book learning" is that it gives one a framework on which to hang all his practical experiences.

how does anyone go about "rationally" analyzing such problems?

See the cracked solder spots .

But that's part of the issue. A close visual inspection can be useful, but it consumes a lot of time and is not "rational" -- that is, it doesn't connect symptoms with possible causes. It's more an act of desperation. (That is not an implied criticism. I'm a great believer in the "try anything" approach to servicing, and often have to fall back on it myself.)

With a good eye, one can scan a whole board fairly quickly for cracked soldering, and combined with poking and prodding a live set with an insulated stick can help to narrow it down. Once you've seen a few of these, it becomes a matter of Ok this is another one of these sets, better resolder the tuner grounds and see where that gets me. Once I started repairing CRT displays, I found that most of them started to look pretty much the same on the inside, and the same half dozen or so problems crop up on 95% of the defective units.

Popular Science magazine used to have articles in Popular Science every month by a radio tv repairman guy in New York City.Not sure if I remember his last name, Art Margulis, something like that.I still have some of those old Popular Science magazines around here somewhere.I used to read his articles every month.His articles were always amusing, sort of like the Gus Wilson Model Garage monthly articles that used to be in Mechanix Illustrated magazine and the Tom ''Chrome Dome'' McCahill auto road test articles in Mechanix Illustrated. cuhulin

Art Margolis. Thanks for reminding me. He seemed to know what he was talking about.

Assuming you are soliciting opinions on this...

It seems to me that the answer to the question: "Which is more important, a thorough understanding of electronics or a great deal of experience?" depends upon the stated goal.

If the goal is to (eventually) be able to troubleshoot and repair anything that comes in the door, then I would cast my vote for technical knowledge. For instance, in the case of the OP's problem, it would seem to me that if poor solder joints on the tuner shielding are really the problem, given a thorough understanding of how all the circuitry works, one should be able to use a scope to examine signals at various points and eventually ascertain that the tuner's output is floating or whatever. (This is just an example, let's not get into issues about whether or not one can probe into a tuner and even see the actual signals.) So let's say for example it took 2 hours of troubleshooting to find it.

OK, so now let's say that the goal is to be able to quickly and profitably repair the majority of products customers are likely to have - then it would seem that experience would be at least, if not more, important. If I get 10 sets in a row like the OP's, and I have a less thorough electronics background, it might take me 3 or 4 hours to fix the first one. But I'll be able to repair the next 9 in 1/2 hour.

OK, there's my two cents. If this was ridiculously obvious, my apologies.

Actually, Gus Wilson's Model Garage articles were in Popular Science magazines.It's been a long while, I sort of forgot.I remember one time a customer's tube type car radio (Model Garage article) was making a buzzing/huming noise.Gus Wilson removed the buzzer and he temporaily connected it to 115/120 volts AC current.That fixed the buzzer. cuhulin

That wasn't exactly the issue. It was really "How in the name of heaven does someone resolve a problem when the defective component has no apparent connection with the problem?"

In this case, why should bad solder joints on the tuner case produce these visible effects? All the book-learning is not going to help much.

My attitude -- as a degreed EE -- is that I want to _understand_ what the problem is. But it can take hours to figure out exactly what's going on. Often, intelligent shot-gunning will get the unit up and running far faster than meticulous analysis. Any successful service tech has to get those sets in and out quickly if he's going to stay in business.

By buzzer, I assume you mean vibrator.

Yep, the vibrator.Gus Wilson's Model Garage and Art Margolis articles in those old Popular Science magazine articles I used to read.You can read a lot of those Gus Wilson's Model Garage articles on the net.I guess it is like that married Irish woman way over yonder across the big pond once told me, I am getting old and senile. cuhulin

"William Sommerwerck" wrote in news:HYCdnUta_7ZY4cTanZ2dnUVZ snipped-for-privacy@comcast.com:

Perhaps the tuner case provides a good ground path for a bypass capacitor in the vertical sync circuit?

--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+spr@ch100-5.chem.lsu.edu   remove ch100-5 to avoid spam trap

No need to speculate on this one.

See:

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Thanks for the information. I'm glad to see there was a class-action suit.

But the speculation remains. There is (for me) no obvious connection between bad solder joints in the tuner shield and the symptoms described.

All the more need for open-mindedness when working on a product, and a willingness to "try anything".

The tuner shield was the ground return path for several critical circuits.