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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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20th Feb 2018, 12:34 am | #41 |
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Re: The oddest valve? KLL32
I thought that the Mexican bus radio would cause some thought, its the strangest valve line up, massively complicated it would seem.
I was considering whether there was a PA function as well or a mid-tuning noise suppression circuit. Can't find a diagram. |
20th Feb 2018, 1:48 am | #42 | ||
Nonode
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Re: The oddest valve? KLL32
Quote:
The TV tuning indicator did involve some complexity, in that the magic eye could not be fed direct from say the vision AGC line. Typically, a sidechain vision IF stage was required, with a relatively narrow bandwidth centred on the vision IF. But the tuning of this stage was not quite straightforward, as the tuning needed to adjusted to offset the effect of the Nyquist slope so that the peak was at the vision carrier and not displaced from it, and also was reasonably symmetrical about it. Then a rectifier was required to provide a negative DC bias to the magic eye. Quote:
Cheers, |
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3rd Mar 2018, 7:31 am | #43 |
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Re: The oddest valve? KLL32
I have a tuning eye on a Loctal base, no number visible. Any ideas what it is and which sets it was used in?
I would assume, probably wrongly, that it would be American sets. |
3rd Mar 2018, 9:26 am | #44 |
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Re: The oddest valve? KLL32
Probably an EM71. European I suspect. J.
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4th Mar 2018, 2:10 am | #45 |
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Re: The oddest valve? KLL32
The Radiomuseum lists EM71 and EM71A with 307 sets and 48 sets using respectively.
There is one set listed, Schaub Supraphon that has one of each! There is also a 12v heater version the HM71 but I cannot find any set that used it. As these are mostly German sets I am surprised, I was unaware of so many Loctal valves being used in continental sets. |
4th Mar 2018, 9:45 am | #46 |
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Re: The oddest valve? KLL32
It does seem out of kilter, I think of the loctal base as a (just) pre-war US Sylvania development, though the very similar principle B9D was famously a Philips thing. The main advantage of a loctal magic eye would be that it would be short, fitting in with the post-war trend for sets to be more compact, possibly the EM71 represented an evolution of the separate-base EM11 in this respect with a base for which tooling and sockets already existed.
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4th Mar 2018, 10:51 am | #47 |
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Re: The oddest valve? KLL32
D'oh! B9G, not B9D.
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4th Mar 2018, 1:23 pm | #48 |
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Re: The oddest valve? KLL32
The EL34 power pentode is a rebased development of the EL60 which was electrically identical except it has an EF50 type B9G base.
https://www.radiomuseum.org/tubes/tube_el60.html An early version of the EL34 was a strange looking valve: https://www.radiomuseum.org/tubes/tube_el34.html DFWB. |
4th Mar 2018, 4:19 pm | #49 |
Hexode
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Re: The oddest valve? KLL32
There was also a UM 71 as well as the HM 71 as per the link below.
Regards Trevor www.magiceyetubes.com |