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  #1  
Old 05-30-2005, 09:08 PM
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Just out of curiosity, what kind of color bar generator makes those annotated bars?
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Old 05-30-2005, 09:30 PM
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Old 05-31-2005, 08:37 PM
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Quote:
Originally Posted by old_tv_nut
Just out of curiosity, what kind of color bar generator makes those annotated bars?
I kinda wondered if someone might notice that. It's a B&K Television Analyst. It has a flying-spot scanner consisting of a small CRT (which glows with a odd-looking dim purple-ish light... its output isn't UV or something is it..?) with a phototube sensor set a few inches away. There's a holder mounted in front of the CRT for inserting tranparancies. The phototube sensor measures light from the CRT as the CRT scans a plain raster, thus generating a video signal based on whatever image is on the transparancy. These things originally came with several different transparancies, including various dot/line patterns and a version of the ever-popular "Indian Head" test pattern. While this sort of flying-spot scanner is only capable of producing B&W images (I'm not sure it can even make grey-scale images; I haven't tried that yet), most? all? TV Analysts have a built-in simple ungated rainbow generator, which if enabled and used with the appropriate "color bar" slide, makes for something that looks like a gated rainbow with nifty labels for the colors. Oh, and it also has a simple audio oscillator to provide a test tone on the sound carrier.

I've seen these TV Analysts show up at hamfests for years (usually at near-giveaway prices), but for whatever reason never bothered to pick one up until a couple of weeks ago. I wish I had earlier-- I never quite realized just how versitile it is! Not only can it generate arbitrary patterns on its scanner, but it can output them in a variety of ways-- either use its built-in modulator to produce RF (at any VHF channel-- later versions of the Analyst could even output on any UHF channel as well) or produce directly at IF frequencies (tunable over a wide range too!), or a plain detector-level video signal. It can even be used to provide substitute sync signals to a TV, or vertical and/or horizontal sweep signals. The video sweep rates are even adjustable over what appears to be a fairly wide range. I'm not sure (I don't have the manual, unfortunately), but I suspect it can even directly produce a substitute HV sweep (from an 'extra' horizontal output tube inside the Analyst) to a TV for troubleshooting purposes.

There appear to be a variety of other things this puppy can do, but without the manual, I'm not quite sure what they are.
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Old 05-31-2005, 09:34 PM
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I have one of those B&K TV Analyst. It has turned out to be a really handy tool in finding bad components. I have used mine on b&w sets. With a test pattern inserted, you start at the antenna terminal. If no picture there, move to the IF stages, If no picture there, you move to each following stage until you finally get a picture. Then, back track just a little and find the bad component. It's good to have for sets that have a hard to find problem.
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Old 05-31-2005, 09:34 PM
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Originally Posted by andy
If you don't want to replace every paper cap, you need to get a cap tester that will measure leakage under full voltage. Sencore made a number of models which work well for that. I can almost guarantee that you'll find out every paper cap is bad. Not totally recapping a 50's TV is like restoring a 50's car and leaving the original rubber hoses, belts and tires on it. Sure, you might be able to get away with it for a while, but it will be unreliable and won't perform as it was desgined to.
Yeah, I've got a couple of those capacitor testers (one Heathkit and one Knightkit), and I must say they're really handy, since, as you say, they can test for leakage at full voltage. I've encountered high-voltage caps before that test great at 25V, but that quickly deteriorate once you get the voltage up past 100V. Usually it's a reasonably quick and helpful tool. In this particular case, though, the "bad guy" cap in question tested just fine at the maximum test voltage, so I didn't figure it to be the culprit. I guess it's just another reminder that test equipment doesn't necessarily reflect actual circuit performance..! I've also got one of those Sprague 'Quick-Check' testers that can check caps for opens and shorts even while in circuit.

As for the recapping philosophy, I can understand your point, and I realize that you're not alone in your opinion, but on the other hand, I'm not entirely sold on the analogy. Belts, hoses, and tires were always intended to be "consumable" parts on a car (take a look at what's not covered on the warranty of a new car!). I think a (somewhat) better analogy to completely re-capping a 50's TV would be that of replacing the carburator and fuel system along with the distributor, alternator, the wiring, and the rest of the electrical system on a 50's car all with equivalent components from a more modern car regardless of the condition or functionality of the original components. Sure, you may save some time and end up with a more reliable car, but one look under the hood will make the more modern replacements stand out and appear out of place. It's really a trade off, and one that I realize can be rather touchy and has its proponents on both sides. (Sorry!) On the one hand, I like to keep my vintage electronics close to as "original" as practical, but on the other hand, I also don't go so far as disguising modern components inside old shells (though I certainly don't have a problem with those who do). Since this set isn't intended to be a "daily driver", and I'm not in a big rush to finish, I think it's reasonable to try to keep things as original as is practical and safe. [If I was planning to run this TV for several hours a day, I'd be more likely to agree with your sentiment, but since I'm not...] Also, I tend to be of the "if it ain't broke, don't fix it!" mindset. Besides, if I just went and replaced everything wholesale, I'd miss out on most of the whole "troubleshooting" part of the project, which can be an educational experience all in of itself, even if it is frustrating at times.

Anyway, feel free to disagree!

PS: The chroma section of this set has very few paper caps (most of them are ceramic discs), and I've already tried replacing two of the more suspicious paper caps anyway, so I tend not to think it's a paper cap at fault in this particular case.
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Old 05-31-2005, 10:53 PM
peverett peverett is offline
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Once you loose an irreplaceable power transformer in an early TV because of some "original" capacitor that you did not replace, you may change your mind!!! Personally, I would rather have a working set with some non-original caps than something that can only be a display item.

If it was built before 1960, I replace all paper and electrolytic caps. I tried leaving an original paper capacitor which had all of 4 volts on it in a 1953 Emerson that I restored. Sure enough the AGC began giving troubles and replacing this capacitor fixed it.
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Old 05-31-2005, 11:14 PM
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  #8  
Old 06-01-2005, 06:25 AM
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Chad Hauris Chad Hauris is offline
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This may be a little bit of a bone of contention for me but the equipment I mostly work with is in kind of a different situation.
We generally replace all paper and electrolytic caps and selenium diodes in tube type equipment...you will have problems crop up eventually with these old caps/rectifiers if you don't.

Some of our tube type equipment really still works hard for its living doing 12 hr. or more a day constant service such as our jukeboxes and PA amps...replacing all those old components keeps this industrial/commercial equipment performing like it ought to. We want to give the same kind of reliability to our clients when refurbishing old equipment so they can use it as much as they want without having to "baby" it.

The cost of caps is insignificant to just go ahead and recap the equipment completely while you have it disassembled on the bench as opposed to having call backs because of problems cropping up due to flaky old components. Much of the tube-type equipment we work on is not collectors items but units going back into a real "working life" so reliability is paramount.
Even if the equipment is only used occasionally, replacing old caps and rectifiers ensures that there will not be anymore degradation of the old parts causing more problems.
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  #9  
Old 06-02-2005, 07:17 AM
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New thread material?

Wow, what an interesting and intriguing statement: “Much of the tube-type equipment we work on is not collectors items but units going back into a real "working life"....

Even 50-kW broadcast transmitters are solid-state today!

Perhaps, Chad, you can give us further insight into the use of tubes in today's society. Obviously the audio crowd takes a big slice of the tube pie (is this not AudioKarma after all), but what other – including commercial – uses of tubes are there today in your experience?
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  #10  
Old 06-02-2005, 08:12 AM
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Some of the tube type products going back in to full time service that we have worked on include Hammond organs, Baldwin organs, jukeboxes (for home use), Gibson and other guitar amps, stereo amplifiers and receivers, and console stereos. These units are carrying on for the most part the service they started out with, however most tube type jukeboxes are no longer on coin routes but in private homes.

AM Antique radios and small phonographs tend to be items people use more for special occasions or for sentimental value as they don't seem to fit in to modern life in the way they once did. Have had only 2 tube type TV's come in for repair...it seems like most people have gotten rid of tube type sets but there are a few customers who still have them in addition to modern sets.
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Old 06-02-2005, 09:37 AM
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Chad use the salient word, "reliability". When I restore a 1940s B&W TV, or a 1950s color TV, I replace all the wax paper and electrolytic capacitors. I often test the wax paper caps as I remove them, and many of them show low leakage, and would work fine in many applications. But what I want most of all is to improve the reliability of the TV I am working on. If you leave the "good" wax paper and electrolytic caps in the set, it is cretin that you will be back in the set sooner than later hunting for the bad component.

Of course, replacing all these caps only improves your reliability so much. The set is still full of old parts, which have high failure rates due to the effects of time and use.
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Old 06-02-2005, 10:30 AM
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I have a couple of the B&K Analysts, the older one seems to have HV problems. The newer one doesn't seem to work right either but I haven't really played with it much. I should, since its been sitting there taking up a big chunk of my bench for a couple years now! I got it from the local TV/Appliance shop when the owner retired, it had been sitting on a shelf in the back room for so long that he didn't know what it was, and neither did I at first! Up on that shelf it looked like a high-end shortwave receiver!

In general, on anything from the 50s or older I replace all the caps I can. Some, in particular, are a real pain to take apart, so why have to do it twice? Changing caps can be fun, anyway. I haven't changed many caps on 60s sets, usually I wait for a problem to arise.

Going along with what Chad said, there are a number of tube organs around. I looked at one for my insurance agent awhile back (needs a motor) & our church organ is tube type. I use a tube amp for various Lions Club events (since some creep stole the solid state amp we used to have). Right now I am working on rigging up a second amp so we can call bingo plus make announcements out on the carnival grounds. The main amp I've used is a Muzak unit, 20 or 25 watts. I have a big, bad 75 watt Muzak that I bought for 50 cents (same price I paid for the smaller one!) but this one is missing all the tubes. When I started adding them up (all industrial types) I decided to shelve it. Now I'll try an old David Bogen unit that just needs the 6L6's. Anyway, from other forums I have read that there are quite a few radio stations still running tube equipment.

Of course, the goofy things I do (like with those amps) don't count, I'm the guy sitting here in the office listening to Benny Goodman on a '42 Airline that I fixed up for a friend.
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Old 03-04-2007, 07:01 AM
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Adding a line fuse and strategically-placed B+ and/or cathode-circuit fuses (pigtail fuses hidden under the chassis with clear heat shrink tubing slipped over them, for example) tends to minimize risk of catastrophic failures, even with some marginal capacitors left in place. What I typically do is add some safety features and as much preventive recapping as my clients are willing to pay for, which tends to vary somewhat. For items in my private collection, I add safety devices and perform needed repairs first, then recap as preventive maintenance as time permits. Some years ago, tubes were rated with TWO sets of ratings, designated "CCS" for "Continuous Commercial Service" and "ICAS" for "Intermittent Commercial/Amatuer Service" and many of the devices we AK members restore are actually transitioning from the continuous use for which they were initially designed to intermittent use.

Paper capacitors which show visible signs of "hot spots" (bubbles in their wax coating) and those which are responsible for crummy performance and/or out-of-spec readings during a check of tube pin voltages are the first ones I replace. Any significant change in the set's performance is a sign to me that it needs to be inspected more thoroughly at some point, and I've had good results with having adequate advance warning of performance issues. Anything from a sudden onset of touchy sync to a blown fuse will get a set in my collection tagged for a trip to the workbench at my earliest opportunity.
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Old 03-04-2007, 07:01 AM
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Adding a line fuse and strategically-placed B+ and/or cathode-circuit fuses (pigtail fuses hidden under the chassis with clear heat shrink tubing slipped over them, for example) tends to minimize risk of catastrophic failures, even with some marginal capacitors left in place. What I typically do is add some safety features and as much preventive recapping as my clients are willing to pay for, which tends to vary somewhat. For items in my private collection, I add safety devices and perform needed repairs first, then recap as preventive maintenance as time permits. Some years ago, tubes were rated with TWO sets of ratings, designated "CCS" for "Continuous Commercial Service" and "ICAS" for "Intermittent Commercial/Amatuer Service" and many of the devices we AK members restore are actually transitioning from the continuous use for which they were initially designed to intermittent use.

Paper capacitors which show visible signs of "hot spots" (bubbles in their wax coating) and those which are responsible for crummy performance and/or out-of-spec readings during a check of tube pin voltages are the first ones I replace. Any significant change in the set's performance is a sign to me that it needs to be inspected more thoroughly at some point, and I've had good results with having adequate advance warning of performance issues. Anything from a sudden onset of touchy sync to a blown fuse will get a set in my collection tagged for a trip to the workbench at my earliest opportunity.
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Old 03-04-2007, 09:01 AM
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Quote:
Originally Posted by jshorva65
What I typically do is add some safety features and as much preventive recapping as my clients are willing to pay for, which tends to vary somewhat. For items in my private collection, I add safety devices and perform needed repairs first, then recap as preventive maintenance as time permits.



John,

I have to disagree with you on both counts, except the safety issues. When I get a request for restoration on any piece of equipment, the first thing I tell the owner is that I will only do a "restoration", complete replacement of all caps, resistors that are more than 20% out of tolerance, and any piece that looks or smells like it has been over stressed. I won't do a "just make it play" repair, yes it is more expensive, but I really don't want to see the piece again. I can count on one hand the number of sets that have come back to be worked on again, and they are usually due to owner "issues", or because I didn't follow my own rules and decided to cut corners and leave a part in that "seemed" to be good. This is especially important with my customers who are dealers and are selling the set to the general public.

The items in my own collection get a full restoration when I have the set opened up the first time, again I don't want to go back into the set again.

As John F. pointed out there are many other parts in the set that can look, smell, or feel OK when you are doing the original work, but can and probably will fail at some point due to age and other issues that can't be controlled, i.e. #1 failure after the fact = tubes.

BTW, I have done a few restorations where everything except the transformers, coils, tube sockets, and parts unique to the set were replaced. Was it worth it? I really don't know, but the customer was happy (except maybe for the dent in his wallet) and I like to believe he has a set that works as good as new and it will continue to work that way for another 50-60 years.


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