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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Tue 03, 2018 4:11 am 
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Regarding all of the discussion of the 6X5GT and 6X5WGT....

First, the problematic tube is the 6X5G as used in some Zenith radios, not the 6X5GT, which had some improved construction.

The "W" suffix does not specifically mean "ruggedized". To quote from the RMA/EIA, the "W" suffix is applied to military tubes whose specifications are somehow different from their registered counterparts.

For many receiving sized tubes made for the military and having the "W" suffix, a resistance to vibration specification was added, so indeed these are ruggedized.

"W" suffix tubes were not registered, unless they became commercialized.

For example, the 6AQ5W was commercialized and registered as the 6005. And there is a 6005W that is somehow different than the regular 6005.

In the world of 12AT7s, the 12AT7WA was commercialized and registered as the 6201. The 12AT7WA was the Army tube. The 12AT7WB was the Navy tube, and the 12AT7WC was the Air Force tube. People often make the mistake of thinking the "C" must be the "most improved", but these simple differ from each other in the bogey specification and acceptable range of the plate current.


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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Tue 03, 2018 4:21 am 
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My vote was the 6SC7. Never seen one that wasn't terribly microphonic, and they were always used in audio circuits.

Dennis

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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Tue 03, 2018 4:59 am 
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azenithnut wrote:
One thought.

With some careful work, you could break apart a dud 50C5, wire the base button to a small Octal socket and sub in a 50L6G
Granted this will only work if there is enough room.

-Steve


I've had almost as many problems with 50L6. It seems like the higher the filament voltage, the higher the chance for shorts--I'm guessing maybe due to the breakdown of the insulators at higher temperatures? I've had better luck with 35C5/35L6

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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Tue 03, 2018 6:16 pm 
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You must be doin' something wrong. :lol:

I've used radios with 50L6 as daily players and transmitter monitors(24/7 duty). I only remember one failure and it was orig 50L6 in a AA5 Admiral. That same radio did go through five 35Z4/35Z5(no dial lamp, works with either). Three were high mileage, including one original to radio. Two NOS lasted 14 & 9 months. At that point I switched to 45Z5 but wound up retiring radio a couple months later. In it's service, excepting for 12SA7 had failures of all tubes. It's Philco PT-30 replacement with 35Z3 & 50L6 ran two years with no failures. The 50L6 was fairly fresh, all others original.

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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Sat 07, 2018 12:02 pm 
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everyone missed the most failure prone of all.
the 6gh8.
i used to buy them by the hundred.
hard to touch an american color tv without replacing a few.
some sets they were all bad!
and even new there was a 10% doa rate on some batches of new ones!
this applied to the series string versions too like 5gh8.
as for 35w4 most bad ones were caused by shorted filter caps or a b+ short.
a combination rectifier/vacuum fuse!


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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Sat 07, 2018 12:23 pm 
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kc8adu wrote:
everyone missed the most failure prone of all.
the 6gh8....


RCA used a ton of them in the early color sets. It was my understanding that a 6GH8 manufactured by RCA did not hold up well possibly because they were run hard. Later production sets used Sylvania manufactured 6GH8 tubes, labeled "RCA" because they were tougher.

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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Sat 07, 2018 12:26 pm 
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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Sat 07, 2018 7:26 pm 
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The RCA 6GH8 was the first tube made by RCA to be made on a totally automated line... raw parts in one end, completed tubes out the other...

Everyone's 6GH8s were better.


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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Sat 07, 2018 8:41 pm 
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I never knew there was a 6GH8 issue, at least till I started moonlighting. Sears Warwick built sets used Sylvania plus a few imports. I don't remember what was used in the Wells Gardener clones that WT Grant sold, but don't remember any real issue.

Got my initiation on a neighbors CTC24 that used seven 6GH8. First time I serviced it I believe all were bad.

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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Sat 07, 2018 10:27 pm 
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Jim Cross wrote:
The RCA 6GH8 was the first tube made by RCA to be made on a totally automated line... raw parts in one end, completed tubes out the other...

Everyone's 6GH8s were better.

Thanks Jim. Is that your same understanding about RCA using Sylvania 6GH8 tubes?

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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Sat 07, 2018 11:00 pm 
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RCA ceased tube production in 1976, but continued to sell tubes up into the 1980s. They bought from several different companies.


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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Sun 08, 2018 1:31 am 
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Don Cavey wrote:
Jim Cross wrote:
The RCA 6GH8 was the first tube made by RCA to be made on a totally automated line... raw parts in one end, completed tubes out the other...

Everyone's 6GH8s were better.

Thanks Jim. Is that your same understanding about RCA using Sylvania 6GH8 tubes?

I haven't seen a RCA that was Sylvania built, but I have seen a OEM RCA 6GH8A built by Westinghouse.

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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Mon 09, 2018 1:56 pm 
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Looking at the "Ink" on these guys, I am sure that they were manufactured by Sylvania for RCA. But I have seen GE tubes labeled "RCA" as well. We all know that toward the end, everyone was sharing the manufacturing and selling to each other.

I was not able to find any pictures of 6GH8 tubes with the RCA "Stop Sign" marking.


Attachments:
6GH8A.jpg
6GH8A.jpg [ 30.76 KiB | Viewed 178 times ]
6GH8A2.jpg
6GH8A2.jpg [ 85.73 KiB | Viewed 178 times ]

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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Mon 09, 2018 2:00 pm 
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Here is one of the early ones, from 1967 I believe. Is this the one that was so maligned? If you look through the glass, it appears to be an RCA. I don't see the manufacturer number on the tube.


Attachments:
6GH8RCA.jpg
6GH8RCA.jpg [ 75.54 KiB | Viewed 178 times ]

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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Mon 09, 2018 7:06 pm 
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With a JP warranty code, those Sylvania built tubes were distributed after RCA stopped manufacturing tubes.

Latest listing in link is FY for Dec 1976. FZ should be Jan '77 and keep counting. I suspect "I" was skipped.

http://www.antiqueradios.com/forums/dow ... p?id=79324

BTW yes the 1967 coded 6GH8A is from era that gave issues.

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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Mon 09, 2018 8:41 pm 
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35Z5 wrote:
With a JP warranty code, those Sylvania built tubes were distributed after RCA stopped manufacturing tubes.

Latest listing in link is FY for Dec 1976. FZ should be Jan '77 and keep counting. I suspect "I" was skipped.

http://www.antiqueradios.com/forums/dow ... p?id=79324

BTW yes the 1967 coded 6GH8A is from era that gave issues.


Thanks Tom, I like hearing about this stuff.

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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Tue 10, 2018 7:10 pm 
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Yes Don,

Those 6GH8s branded for RCA were made by Sylvania. You are correct about the bulb printing...

For the "big 3"

Octagon with USA under it means RCA
Thin script, no octagon, with USA means Sylvania
Sandblasted number with dots under means GE

The other "tell" is the font of the type number printed on the box. GE and Sylvania both used a different font than RCA

The place where one might see a mixture of the three branded RCA is in a tray of NOS 6JE6Cs and 6JS6Cs.


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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Wed 11, 2018 8:12 pm 
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My nominee for worst_tube_ever is the 6Q7 and its 12-volt equivalent. They had extremely close spacing between their detector diode plates and the cathodes. Debris would get lodged between the plates and the cathode, shorting them out. Sometimes all it would take is a sharp rap or bump. 60-cycle hum bleeding through from the heater was another a problem with many of them. Many tube testers could not pick up on the subtle leakage or bleed-though; you had to swap them to find out if they were causing trouble.

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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Thu 12, 2018 1:34 pm 
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I can say in my time collecting and daily using tube radios (a few AA5 sets are in my office at work and run for up to 8 hours at a time) I have not seen a single 50C5 failure. If you go by results on a tube tester, I have personally observed a 1954 RCA where the 50C5 tests solidly in the red (replace) Zone on my Hickok 533A tester yet plays at normal volume and sound in the set. That was over a year ago, and I have been running that in the work office rotation since that test and the set continues to work fine.

If I can find that elusive “copious spare time,” I’ll post my records of tube failures since I started tracking them. Overall the vast amount of failures are in newly acquired sets where “as found” I can count on encountering a bad tube or two. No surprise there since odds are good that whatever failures sidelined the set could or would likely take out a tube in the process (or the set was used longer than I have been alive and the tubes finally lost emission).


Joe


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 Post subject: Re: Was there a worse tube ever made than 50C5?
PostPosted: Jul Fri 13, 2018 9:07 pm 
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here is my list of (not tv) tubes that nearly always have "the worst" emissions and/or gM in a barn fresh set based on my experiences:

6BQ5, 7868, 6SG7, 6SD7, 35L6, 42, 45, 6CA7, 19T8 (all 47 sections of it), 12BZ6 and I'm sure a few others that I can't thing of right now.

steve

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