Playing with 2 Volt valves

[AdrianPH]

I have been reading articles that were around in the 1920's using typical battery valves after I picked up a few recently.  So today I finished building a single valve receiver using a  Cossor 210HL valve.  To be honest it has surprised me that a single simple triode can do HF amplification, detection and drive a pair of headphones.   OK it uses regen to provide the amplification and it can be a bit tricky to get on the edge and it needs a good piece of wire.  I would think many of you have played with these simple radios before, but to me it is still impressive reception.

The next step would be to add another valve for some audio amplification, but need to sort out some extra transformers of the correct style.

https://youtu.be/i5vOPqr1IPE


Adrian

       

[joebog1]

Your wiring and layout look nice!!. ( I have never seen an electric wireless from the 1920's ).
Its very similar to pics I have seen on the net.

Joe

[AdrianPH]

Thanks Joe, this is just me playing with what bits I have picked up, so layout is not that good. I have seen a few radios on Ebay which seem a lot more compact and nice fronts etc. Perhaps if a two valver works well enough I will find a suitable box to make a better reproduction one.

Adrian

[roadster]

That is nice Adrian,
I enjoy building similar sets, but generally  modify them several times then use some of the parts for the next one, so they are not as neat as yours. I also have several 1920s/30s built sets, including one which had with it, a beautifully hand written list of stations and the apprpriate dial settings. The only commercially built one is a Cossor Melody Maker; the rest being home made or from kits (Scott-Taggart).
Did you wind your own coils and are you thinking of trying short wave? A slow motion drive would be a nice touch and quite useful; they are around and can be found at jumbles for little money.
Rod

[AdrianPH]

Hello Rod,

The central coils is home wound, but does not really have enough turns for the MW band so it has a ferrite rod stuck in it! The outer coil is one from a junk box, it really has too many turns for the reaction coil but it works! I may change things around later to make it neater..

Adrian

[Murphyv310]

Hi.
Not having any 20s 4 pin battery valves these days I replicate the circuits with Soviet Rod Pentodes. Again I find it quite amazing how well a single valve works.
My little two valve regen Rod Pentode radio drives a speaker with good volume.

[AdrianPH]

A similar project using rod valves is still on my todo list. I have an old box or hearing aid batteries and wondered about using a stack of them or LR44 button cells in a tube for HT.

Adrian

[Mike Watterson]

You can even run the dual filament 1.2V x2 = 2.4V off 2 volts and use the 1j29p as a replacement for any 2V triode, screen grid type and pentode. HT of 45V to 90V
Simply increase a filament series resistor if the gain is too high for the original circuit. Strap g2 and anode but g3 to f- or f+ for a triode. Just use it with g3 to f- or f+ in any tetrode/screen grid circuit. The rod tubes are only pentode like, they are not actually Pentodes. The 1j24b works well as a Pentode mixer if the anode of a rod tube wired as a triode oscillator drives and biases g2 directly. The g3 is always to f- or f+, but can give limited gain or mixing action. Because the g2 varies from nearly zero to (Ia at max)to nearly Ia they can be unstable with just a resistor to set g2 volts, but all the old SG circuits used an HT tap to set g2 volts which really suits rod tubes. I've had to add a potential divider (second resistor to 0V on g2) to replace DF91/1T4, DF92, DF96, DF97 in IF or DAF9x preamp (1N60 as diode, which predate DAF96 anyway!)

Note that the ECH83 = ECH81 exactly and many 6.3V valves will work series/parallel off 12 to 14V heater and 12V to 14V HT, though 24V HT is better. ECH81, EF89, ECC81 etc. At 12V HT the grid bias can be +1v.

At regular HT (or even 90v) the ECH81 can drive a speaker as as well as a DL92 could.
You can use a mains transformer at low bias currents single ended for audio, or any bias on a 110-0 -110 transformer with push pull.
A shaver transfomer can work as 1:2 stepup or phase splitter to

[Mike Watterson]

LR44 has too low a current limit. Even the CR2032 is too low for any set driving other than 4K earphones, use 3 stacks paralleled with 1N4148, and fuse on each stack. An 80V stack will go on fire if shorted. About 14c each online.
Use Zinc biscuit PP3 batteries, never Alkaline or lithium. Cheaper and safer!

I'd maybe try Alkaline button cells for HT of a one or two tube rod valve set with a "crystal earpiece". The modern ones are just a ceramic beeper disc, which will work with about 10 K ohms in parallel as a load on a diode radio or simple valve set. Make an insulated earbox for acoustics and safety!

[Murphyv310]

Hi.
My 2 valve rod pentode regen draws 6.5ma from 56v, it uses a 1J24B & 1J29B. Zinc PP3s don't last and I use alkaline ones with no problems.
It was shown off at the recent meet and many were very impressed.
I use it regularly in the shed when working. It feeds a good quality 8 inch speaker and is loud enough that I need to reduce the volume.