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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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19th Aug 2020, 5:15 pm | #1 |
Hexode
Join Date: Feb 2008
Location: Wrexham, North Wales, UK.
Posts: 465
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Yet another mystery valve!
I've just acquired a strange set - it's the basics of a Pye radiogram, with a (probably) home made amplifier tacked on inside.
The output valves are a pair of - what? They have a rope-and-anchor logo which suggests Navy tubes. B7 base, 4 volt heaters. But the pinout is slightly odd: 1 - K? 2 - CG 3 - SG 4 - H 5 - H 6 - K 7 - NC TC - A The only valve I can find with this pinout is the AC6/Pen which is the same as NR74 or CV1189. However, this, according to RM, "a beam power amplifier designed for use with the output stage of a time base for magnetic TV scanning." Presumably they would work as audio output valves...? gm appears to be about 3mA/V. |
19th Aug 2020, 5:20 pm | #2 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
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Re: Yet another mystery valve!
The rope-and-anchor looks rather US-styled - perhaps your amp is made using US-sourced valves (tubes) ??
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19th Aug 2020, 5:24 pm | #3 |
Hexode
Join Date: Feb 2008
Location: Wrexham, North Wales, UK.
Posts: 465
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Re: Yet another mystery valve!
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19th Aug 2020, 5:45 pm | #4 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,385
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Re: Yet another mystery valve!
In pre-war TVs, there was still an expectation of a degree of linearity in timebase output valves (i.e. well before the TV22 etc. trend of the LOP valve acting as a switch), so it's entirely possible that someone thought of using them as audio power valves. Maybe the "navy" logo suggests that an existing valve with good cathode current capability was taken on board (metaphorically and literally) for modulator (linear or pulse), RF PA, series regulator, whatever use and there were a goodly load surplus post-war.
Just thinking aloud! |
19th Aug 2020, 6:01 pm | #5 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,637
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Re: Yet another mystery valve!
Could just be Anchor brand, not necessarily Navy?
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19th Aug 2020, 6:22 pm | #6 |
Octode
Join Date: Dec 2017
Location: Morden, Surrey, UK.
Posts: 1,552
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Re: Yet another mystery valve!
Kt44?
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19th Aug 2020, 6:44 pm | #7 |
Octode
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
Posts: 1,987
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Re: Yet another mystery valve!
Its depicting the foul anchor in its British form.
The U.S. navy later used it and added USN Unity Service Navigation All i can remember from sea cadets.... many years ago
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Stephen _________"It`s only an old telly" ___ |
19th Aug 2020, 6:52 pm | #8 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Yet another mystery valve!
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19th Aug 2020, 10:46 pm | #10 | |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,528
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Re: Yet another mystery valve!
Quote:
Apart from the base and a couple of very minor differences, the datsheets from Mazda look identical. A p-p pair should be good for 20W+.
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19th Aug 2020, 11:00 pm | #11 |
Octode
Join Date: Feb 2009
Location: Bletchley, Buckinghamshire, UK.
Posts: 1,205
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Re: Yet another mystery valve!
I'd say it's an AC6/PEN - or the Navy version, NR74.
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20th Aug 2020, 12:10 am | #12 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,997
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Re: Yet another mystery valve!
I would agree with Lawrence, there are some Mazda AC6/PEN on ebay https://www.ebay.co.uk/itm/Quad-4-Ma...AAAOSwZoVeSxxb
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20th Aug 2020, 9:21 am | #13 |
Pentode
Join Date: Feb 2015
Location: Chepstow, Monmouthshire, UK.
Posts: 234
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Re: Yet another mystery valve!
I have a small collection of different AC6/PENs.
Looking at the pictures, I would say it is definitely a late 40s/50s AC6/PEN, or the same date NR74, as they're identical. Pre-war production AC6/PENs had different holes on the anode. Photo 1 shows on the left a late 40s/50s AC6/PEN with a pre-war AC6/PEN on the right. Photo 2 shows the same valves viewed from the top. Photo 3 shows the later AC6/PEN with a British military NR74. They are identical. Photo 4 shows an American Raytheon NR74. As you should see the construction is very different. The AC6/PEN was used in pre-war televisions, and was a more powerful version of the AC5/PEN. In the Murphy A56V television of 1938, the AC5/PEN was used as the audio output valve, and the frame timebase output valve. The AC6/PEN was used as the line timebase output valve where more power is needed. I see no reason why it couldn't have been used as an audio output valve. |
20th Aug 2020, 9:58 am | #14 |
Pentode
Join Date: Feb 2015
Location: Chepstow, Monmouthshire, UK.
Posts: 234
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Re: Yet another mystery valve!
I forgot to mention, the reason why the anode is brought out to a top-cap, and kept separate from the other pins (unlike the AC5/PEN), is due to large back emf voltages when used as a line timebase output valve. During line scan flyback, large emf voltages flow back from the deflection coil, of about 2,000 volts, and the valve has to be able to handle that.
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20th Aug 2020, 9:59 am | #15 |
Heptode
Join Date: Apr 2010
Location: West Midlands, UK.
Posts: 659
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Re: Yet another mystery valve!
Isn't the PEN46 basically the same valve as the AC6/PEN updated with a Mazda Octal base.
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20th Aug 2020, 10:01 am | #16 |
Pentode
Join Date: Feb 2015
Location: Chepstow, Monmouthshire, UK.
Posts: 234
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Re: Yet another mystery valve!
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