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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jun Wed 13, 2018 8:47 pm 
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is there any truth to this statement:

operating a radio with a weak audio output tube can cause stress on other components.

IDK whether this is hogwash or not, and it matters not to me b/c i don't do it, but hopefully someone can confirm it for curiosity's sake.

i heard/read this somewhere.

steve

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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jun Wed 13, 2018 8:58 pm 
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Steve

Although I don't remember seeing it a weak output tube can put stress on other components. When an output tube is weak emission will be down. This causes the tube to draw less current. Less current allows higher voltage on the B+ line for other components.

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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jun Wed 13, 2018 9:32 pm 
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I've not heard of such a thing, and have not found it to be true.

I do remember many years ago hearing about installing a new CRT in a TV puts stress on the rest of the set's older components.

Again, I've never seen any proof to this concept.

-Steve

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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jun Thu 14, 2018 2:05 am 
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understood

steve

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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jun Fri 15, 2018 2:53 am 
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How about the 50A1 ballast used in some Transoceanics?
John

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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jun Sun 17, 2018 12:31 am 
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The engineers over at Majestic (Grigsby-Grunow) had a thing for odd tubes, such as the spray-shielded types, the G-2-S and G-4-S detector diodes, the G-84 rectifier (half an 80), and many others that were unique to that brand.

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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jun Sun 17, 2018 12:35 am 
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I believe those off spray shield tubes were actually Canadian origin with the Rogers-Majestic connection.

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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jun Sun 17, 2018 1:06 am 
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Quote:
Sparton produced a special tuning indicator tube for some of their 1935 models called the VG-1. (Viso-Glo)

So that's what that odd little tube I've had for years is! Until now I had no idea what it was or what set it was used in!

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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jun Sun 17, 2018 1:11 am 
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The only radios that I am aware of that used the Armor AC100 tube were a couple of early Garod ac receivers, the EA and EM

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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jun Sun 17, 2018 1:39 am 
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RadioKev64 wrote:
Quote:
Sparton produced a special tuning indicator tube for some of their 1935 models called the VG-1. (Viso-Glo)

So that's what that odd little tube I've had for years is! Until now I had no idea what it was or what set it was used in!


Wow, you have one?
My Sparton 136 is missing its tube, if you have any thought as to parting with it.

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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jun Sun 17, 2018 4:09 pm 
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I don't have any radios that use it, so I'd let it go. Bear in mind, however, that I have no way of testing it, so its condition is unknown.

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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jul Sun 15, 2018 5:49 pm 
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bill flaherty wrote:
Curious which vacuum tubes are considered the rarest in Old Tube Radios what years were they made, the type and for what brand and model radios? Bill...Maine


How about the Welsh tubes? I know of two types:

WT-501 (external coil grid wrapped around the middle of the bulb)

Welsh Dollar Detector (looks like an automobile tail light bulb, but with two tiny bent wire electrodes in addition to the filament)


I believe they date from the early to mid 1920's. Probably used mostly by DIY experimenters. I don't know of any commercially manufactured sets that used them; do you?

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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jul Wed 18, 2018 6:12 am 
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Dutch Rabbit wrote:
is there any truth to this statement:

operating a radio with a weak audio output tube can cause stress on other components.

IDK whether this is hogwash or not, and it matters not to me b/c i don't do it, but hopefully someone can confirm it for curiosity's sake.

i heard/read this somewhere.

steve


Weak tube, no but the worst case is an old tube that is getting "gassy", that is, it draws grid current, making it positive and the tube starts to draw more and more current and its like a snowball downhill until the plate glows bright red and burns itself out or the power transformer goes as almost no old radios had fuses.
This problem is most common in the German radios 1957-1964 that were heavily imported to the USA. They used 6BQ5 (EL84) tubes that will pull a lot of current when they begin to fail... this can run on for weeks until the power xfmr is toasted slowly.
Another cause of this is a "leaky" grid coupling capacitor.
Mark Oppat


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 Post subject: Re: Rarest Vacuum tubes for old radios? What ones are rares
PostPosted: Jul Thu 19, 2018 3:15 am 
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thanks mark,

makes sense.

steve

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