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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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30th Mar 2020, 6:42 pm | #1 |
Octode
Join Date: Jun 2006
Location: St Osyth, Nr Clacton, Essex, UK.
Posts: 1,482
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RV12P2000 one-valve radio
This is the first radio I've built for decades but I've been planning it for months. It follows the circuit from February 1964 PW, p 937 & 938. Their version uses a Z63 for the RF stage and a 6J5 for an output stage. I just wanted the RF stage so I've potted down the signal at the anode of the valve and fed it to a transistor guitar amp as this was easiest for me.
I could have tried many valves such as EF91, EF80 - anything really - but I wanted to use a German WWII valve type RV12P2000. This highly versatile valve has its own special valve holder as seen in the photo. All the components surrounding the valve I built onto the valve holder. Having wound the coil using quite a thick gauge of enamel wire I assembled everything onto a prototyping chassis of Lektrokit using M3 pillars to stand it off the table. The disk-drive type power connector supplies the 12v heater of the valve from a non-switchmode wallwart. HT is about 120v using my multi-PP3 WS38 battery. At first there was just rustling/crackling and a bit of microphony when I tapped the valve. I have a bit of a history of forgetting to ground all earth returns and I'd forgotten to connect the earthy end of the reaction winding. That got it going but I needed to thoroughly clean the valve holder to clear the rustling. Earth is mains earth and aerial is about a metre of test probe. I'm amazed at how sensitive it is. Smooth Radio, Absolute Radio and BBC Essex romp in. Sadly, Caroline 648 is not receivable - maybe due to not following the proper coil-winding details. A longer aerial might bring in more LF(?) I'm not too bothered as part of the task is to try much smaller coils. Very happy with my experiments so far and I guess I can recommend the circuit. I liked the idea of an earthed cathode and a pot-based regen control. Graham
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Half my stuff is junk - trouble is, I don't know which half! |
30th Mar 2020, 7:26 pm | #2 |
Octode
Join Date: Aug 2008
Location: Rotherham, South Yorkshire, UK.
Posts: 1,723
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Re: RV12P2000 one-valve radio
Very nice!
I think that is the very first time I have seen one of these valves suggested and then used in a receiver that was not WW2 German! I do believe that the USSR continued their manufacture after the war. Not very common in this country especially the base/holder but I have one sitting on the bench next to my computers. I also have one of the Luftwaffe FUG10 receivers that uses one in every single stage! A generous gift given to me by G3RYF when I was 11. The set is an amazing piece of over engineering; the multi gang tuning capacitor is not made up of individual plates but machined from a solid block of aluminium or so it appears. I see that you also have the correct removal tool for it. Makes a change from an EF50.... Peter Last edited by Reelman; 30th Mar 2020 at 7:27 pm. Reason: Just noticed... |
1st May 2020, 3:19 pm | #3 |
Pentode
Join Date: Jan 2014
Location: Huddersfield, West Yorkshire, UK.
Posts: 129
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Re: RV12P2000 one-valve radio
This valve was manufactured after WWII in East Germany till 60-ties, never in USSR
Russian 12Z1L it's same with different base, 4Z1L and 6Z1L same with different heater. Replaceable by EF95 (of course different heater) |
1st May 2020, 3:56 pm | #4 |
Hexode
Join Date: Mar 2009
Location: Worthing, Sussex, UK.
Posts: 276
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Re: RV12P2000 one-valve radio
That's really nice. I have a box of these little valves - some with swastikas on!
I might try to make this radio but I don't have any sockets. I suppose small croc clips will work. Or even paper clips. Passes the time of day in these locked in days... Ging |
1st May 2020, 7:18 pm | #5 |
Pentode
Join Date: Jul 2009
Location: Roxburghshire, UK.
Posts: 196
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Re: RV12P2000 one-valve radio
I wonder if anyone makes something like that Lektrokit chassis nowadays? It used to feature a lot in PW and Radio Constructor.
A turret press could knock them out by the thousand if there only was a demand. Cheers, Colin. |