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 Post subject: Subminiature 8-pin tubes - any use?
PostPosted: May Thu 09, 2019 7:34 pm 
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There are a number of 8-pin subminiature tubes in the RCA tube manual, mostly for 1.4-volt battery operation. The dawn of the transistor radio put these tubes into obsolescence soon after they were released, I am sure. Is there any use for any of these types for replacing 7-pin miniature tubes for experimental purposes? I was just wondering... These are types 1AC5, 1AD4, 1C8, 1D3, 1E8, 1Q6, 1S6, 1T6, 1V5, and 1W5, just for reference...


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 Post subject: Re: Subminiature 8-pin tubes - any use?
PostPosted: May Thu 09, 2019 10:24 pm 
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Being they are one volt tubes, you might cross some of them to use in something like a tube portable that uses DC filament tubes. Well maybe except for the audio output. See this site: http://www.wa2ise.com/netcom/WA2ISE%20s ... 0page.html As far as I know, they are good for projects. Can be used in alot of projects like simple regen radios, audio preamps, stuff like that. I am sure you could build a sophisticated superhet radio with them, too. I think I have seen plans for basic AA5 type stuff, but not for fancier radios. As far as direct cross reference, I doubt it due to the drastically different physical specs but maybe you could compare and get close enough to allow use with some circuit tweeking. Then there are tons of Russian subminis for really cheap. Good luck with those. Some sites have the specs but who knows how accurate? I am sure they must have been a Soviet secret at one time. Some of the tube manual entries give basic info like audio amplifier stages with component values. I have a box full of subminis here. I have a half dozen of the 6112 dual hi mu triodes and the manual entry shows basic voltage audio amp configurations for that tube.


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 Post subject: Re: Subminiature 8-pin tubes - any use?
PostPosted: May Fri 10, 2019 2:12 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Mt. Prospect, IL USA
Well, okay, it seems like these could be interesting. I was thinking about building portable AM transmitters and AF signal tracing amps just for fun. Maybe installing some below the chassis deck on 1.5-volt battery parts sets, just for kicks. I have used 5676's to sub for the WD-11 tube in my RCA Radiola X "Regenoflex", and they work well there. We'll see what happens. I don't imagine these tubes are common, since most of them went into industrial/military gear; only a few home radios used them, some alongside the newcomer transistor...


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 Post subject: Re: Subminiature 8-pin tubes - any use?
PostPosted: May Fri 10, 2019 5:43 pm 
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Zenith introduced some subminis around 1939, I think, for use first in hearing aids.


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 Post subject: Re: Subminiature 8-pin tubes - any use?
PostPosted: May Fri 10, 2019 6:46 pm 
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Motorola, Emerson, and probably a few other companies made battery and "3-Way" portable radios which used subminiature tubes, so those tubes do have some small value for replacements. RCA made a series of receivers for the Navy--the SRR and FRR-11, 12, and 13 which used six-volt versions of those tubes. They were nice receivers but no match for the R-390 or R-390A. Subminiature tubes also went into various other kinds of communications equipment such as RTTY converters, computer logic boards and even some things like HV rectifiers in certain oscilloscopes.

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 Post subject: Re: Subminiature 8-pin tubes - any use?
PostPosted: May Fri 10, 2019 9:57 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Saskatoon
I've seen a number of simple radio projects using subminiature tubes. Here's one for example:
http://makearadio.com/tube/6418.php


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 Post subject: Re: Subminiature 8-pin tubes - any use?
PostPosted: May Wed 15, 2019 5:09 pm 
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Location: Pasadena CA USA
I do not recall the types used, but PRI used them in some Geiger counters.


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 Post subject: Re: Subminiature 8-pin tubes - any use?
PostPosted: May Wed 15, 2019 5:14 pm 
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Location: Radio Heaven, North Carolina, near Charlotte, 28106-3015
They make good targets for the pellet rifle.

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 Post subject: Re: Subminiature 8-pin tubes - any use?
PostPosted: May Tue 21, 2019 12:05 am 
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You could build a headphone amp with tubes. This kit looks like a lot of fun using 6418s albeit shipping from Down Under is a bit steep for one. Price + shipping on 3 kits is much better per unit, I’d just have to find a couple of kit buddies.

http://oatleyelectronics.com//product_info.php?products_id=1168&osCsid=rpbqknopkn2j4g2v80agrvopo6

CaptQ
Paul

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