RV12P2000 one-valve radio

[llama]

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

[Reelman]

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

[k_yller]

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)

[gingpeakin]

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

[Colinaps]

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.