#76
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That Silvertone metal-cabinet roundie Electronic M has reminds me of a set I had in the early 1970s. Mine was almost exactly identical to his (except for the push-pull volume control and power switch), but I had all sorts of trouble with it. I got the TV from someone in my old neighborhood; when I got the set home, I found a bad circuit breaker. I jumped the breaker (was just starting in TV servicing at the time--besides, I did not have a replacement handy); that got the set working, and in fact I had a picture and sound after that, but I was never able to get the convergence right.
I fooled with the set for three years, trying one thing after another to get it to work as it should, then things started going wrong. First, the color sync went bad, although I could get it to lock by turning the tint control back and forth a few times. Then the video output tube (I think) developed a heater-cathode short, putting a hum bar in the picture. The video output tube socket cracked out of the board when I tried to replace the tube (the only replacement I could find had a bent pin); this ruined the set. I've been wary of PC boards in televisions (or any other electronic device) ever since. I left that roundie behind when I moved in 1975, and replaced it the following year with another Sears rectangular color set which was actually built by Toshiba; that one was followed by a long string of color and b&w sets, all used. However, I don't miss the roundie one bit. Those phenolic-based PC boards may have been good when they were new, but after a few years of being subjected to heat from tubes and such, they became so brittle that changing tubes became a real problem--the least bit of pressure on a tube socket would crack the board, all too often ruining it. I would not dream of touching the PC modules in my flat screen TV (or either of my late-model CRT sets) these days.
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Jeff, WB8NHV Collecting, restoring and enjoying vintage Zenith radios since 2002 Zenith. Gone, but not forgotten. |
#77
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Quality of PC boards has improved over time. I've never busted a tube socket through a board(knock on wood), but then again I know the strength of PC boards, and thus try not to put much force on them...A tube socket on a PC board can't take a person's full weight like a chassis mount socket can.
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Don't worry about tube swap mistakes too much, I still make them occasionally. What drives me nuts is when I don't notice for a long time, or I make the dumb mistake of assuming a tube that was good before a breakdown is still good after the problem....I've wasted many hours chasing my tail on passive components when all that was wrong was a bad tube. Convergence can be a real SOB on some sets. On my roadside sylvania I finally got it back to how it was before the hv failure, but me and a friend decided to try and improve the dynamic convergence and only made it substantially worse....
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#78
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Tube substitutions must never be done haphazardly. Putting tubes in the wrong sockets in a TV, radio or any kind of electronic equipment using vacuum tubes can have disastrous results; for example, the filament pins of one tube may well be the plate terminals of another, possibly causing circuit damage or worse (including but not limited to fire) if two or more tubes are put into incorrect sockets. I would never substitute one tube type for another unless I was absolutely certain the substitution would work. A good rule of thumb is to check a tube substitution manual if you are in doubt as to whether a particular substitute will operate properly. If you do not have such a manual, replace the tube with the same type already in the device you are servicing.
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Jeff, WB8NHV Collecting, restoring and enjoying vintage Zenith radios since 2002 Zenith. Gone, but not forgotten. Last edited by Jeffhs; 10-22-2013 at 02:31 PM. |
#79
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Be absolutely sure that the tubes are in the right sockets before you do anything. I learned the hard way when I was checking out a set that used the 6DT6, 6AU6, 6AQ5 audio board. I was told the sound was fine, then nothing. Someone had switched the positions of the 6DT6 and the 6AU6, and I didn't look at the actual numbers. These tubes look similar, but are not the same. I'm so glad that I have only one set that uses one 6GH8 tube. I never have good service from them, and they have caused more repeat trouble than I care to mention.
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Bruce |
#80
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Back to the original topic of this forum-the tube type sets could be very reliable imho.My father bought a zenith roundie in the fall of 1966 that had nothing but problems in its first 2 years of life(almost always a bad tube).After its last repair of a new crt int 1968,it was played day in and out thru the end of 1979 without a single service call.It was still working when I bought him a new magnavox for Christmas in 1979 but with a weak crt.I mistakenly told him to throw it out when the new set arrived(wish I would have kept that set).The magnavox still plays today-never a service call!
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Audiokarma |
#81
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Afraid to ask but how bout zenith hybrid 1976 25" Early American Got one with 100 hrs on it since bought new by me and in storage 20 yr. I am going to use it in family room. At 61 I am going backwards. Seriously, are these sets safe to power up normally? It has varactor tuning ultrasonic space command. Remember this chassis had modular design. Am I going to go nuts getting this set to work?
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#82
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I wouldn't be afraid to power up a 76 model normally. And I wouldn't be surprised at all if it works fine as is. However, if you have a Variac or some other similar device, it never hurts to bring them up slow. A lot depends on how long it has been dormant.
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#83
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Rule of thumb if your Zenith says CCII(Chromacolor II) or System 3 then it is SS, but if it is just Chromacolor or has no fancy second name then it is tube or hybrid. Zeniths from the 70's tend to be quite reliable...They usually don't die, and instead they develop annoying intermitents that make you wish they would die so you can properly troubleshoot them...
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#84
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My grandparents got a new Zenith 23V in 1974 to replace the 1966 23" color set they wore out. It had a chassis 23EC15 and that was the last hybrid tube Zenith. I think the Florida humidity killed the 66's flyback and I got a report of my Grampa gutting it, placing the chassis/CRT in the trash, then re-purposing the Italian Provincial cabinet, not funny when I would have gladly taken it for parts.
The 23EC15 was sent to my Aunt who had it a few more years, I did little more than test the 4 tubes and clean the tuner on 1 or 2 visits down to see everyone. The 23EC15 was the lower-priced alternative to a CCII, but this one was fairly trouble-resistant. making a picture pretty much like a CCII A few years later I fixed one with the same chassis and sold it, ending up exchanging it for an XL100 because it kept developing issues. I wrote it off as one of Zeniths few dogs.But, of course the CRT was strong.
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"When resistors increase in value, they're worthless" -Dave G Last edited by DavGoodlin; 11-19-2013 at 08:49 PM. |
#85
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It will have the regulating transformer/cap. IIRC as you crank it up it will pulsate then sudently work at abt 85 V at full power. I would just plug it in. As far as other problems go its the easiest old color TV to deal with & parts still abound. It only takes the slightest knowledge to walk through any problem. 73 Zeno |
Audiokarma |
#86
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For what it's worth, I just powered up a 1978 RCA directly without hurting it.
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#87
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I generally plug in anything that was built after 1960.
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