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Do You Want To Build A One Valve Receiver

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Sparks
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I produced a quite comprehensive article recently. Here is the synopsis:

Vintage Radio & Electronics
For The Home Constructor
by
Robert A. Wilson F.R.S.A.
A One Valve Battery Receiver

This e-book shows how to build a one-valve radio receiver using only a few components. It is perfectly safe for all ages, as the power supply is obtained from small 9 Volt batteries connected to make up the required 54 Volts for the high tension supply.
Two versions of the circuit are described. The first one, uses a very old HL2 triode valve. As this type is becoming more rare, a simple modification is described to make use of the far more common EF91 pentode valve instead of the HL2. EF91 valves are still in good supply, and not very expensive.
Some practical skills are required, such as the capability of using a few hand tools, including the use of a soldering iron.
Sources for all the components and materials are given in the book.
This e-book has been prepared with large text and images so that it is perfectly readable in e-readers that can handle PDF documents. That includes Kindles
And Nooks. It can also be displayed on a computer, and printed out if so desired. 58 pages, 6,426 words and 64 images.
------------------------------
It was a complete flop. I then offered it free on another vintage radio website. About two members had copies. The site itself was not interested in it.

If VRAT wants it to put in the site somewhere, I will be pleased to send the file which is complete and with images. It is about 2mb in size.
Here are two two versions that it described.

 
Posted : 28/04/2014 3:03 pm
crustytv
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Hi Robert,

Thanks for sharing that, I would be pleased to place your e-book on the main website I would actually go further than just a pdf but make it a featured radio article.

I would create an article page for the "How To" section which proves quite popular with readers. The title would remain "How To Build a One valve Receiver" but I would convert the E-book into a featured article web-page for public consumption. Hopefully it might inspire youngsters and old hands alike. https://www.radios-tv.co.uk

Last year some of the VRAT team attempted a Minimalist Superhet Radio see here

If you would like to think about it first or are happy to send the e-book, drop me a pm for my details.

Regards
Chris

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Posted : 28/04/2014 3:13 pm
Sparks
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Chris,
I have sent you a PM.
Robert

 
Posted : 28/04/2014 3:50 pm
Anonymous
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I agree with Jeffrey 100%
Rob T

 
Posted : 28/04/2014 4:26 pm
Anonymous
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But only if it uses absolutely common valves.

 
Posted : 28/04/2014 4:27 pm
crustytv
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But only if it uses absolutely common valves.

As Robert clearly stated in the opening post of this thread and with the photo text descriptions, but I will repeat it

Two versions of the circuit are described. The first one, uses a very old HL2 triode valve. As this type is becoming more rare, a simple modification is described to make use of the far more common EF91 pentode valve instead of the HL2. EF91 valves are still in good supply, and not very expensive.

Therefore Michael can we not go there again! You said your piece on the matter of valves in the minimalist Superhet thread, the mods ended up having to remove them all due to you labouring the point. We don't want to have to do that again. I think we've all got the idea of your opinion by now.

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Posted : 28/04/2014 4:50 pm
Sparks
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Thanks for the replies. I sent the 58-page document to Chris a few minutes ago.
The EF91 screen grid is strapped to the anode underneath the valveholder. I am very sure that an EF80 would work as well. Also another of my favourites, the little EF95 pentode. Also, the 6C4 triode (B7G) has given good results. When I completed the HL2 version, I tried numerous four-pin triodes in it, some of which no longer had any visible numbers. Most of them worked OK. I finally settled on the EF91 because it is really common and inexpensive and I have lots of them lying around.

 
Posted : 28/04/2014 5:24 pm
sideband
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It's worth noting that the 6C4 is exactly the same as half an ECC82 which are also very common.

 
Posted : 28/04/2014 9:04 pm
Sparks
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I didn't know that the 6C4 was the same as half of an ECC82! But surely all double triodes seem to be in great demand these days and the prices seem to be escalating?

 
Posted : 28/04/2014 10:18 pm
Katie Bush
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Stretching a point, I know, but this would be a nice way to obtain the valve for the radio....

Marion

 
Posted : 28/04/2014 11:48 pm
sideband
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I didn't know that the 6C4 was the same as half of an ECC82!

According to Brimar, the curves are the same as 12AU7 (ECC82). See here

But surely all double triodes seem to be in great demand these days and the prices seem to be escalating?

The ECC82 seems fairly safe at the moment and prices are nothing like ECC83.

 
Posted : 29/04/2014 12:32 am
crustytv
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I sent the 58-page document to Chris a few minutes ago.

I've made a start, I first extracted all the images which in total were about 78 (including symbols). Then completed 30 pages on the website only 28 left to do. Should be published sometime tomorrow, I will notify here when done. Its a great read and I think those so inclined will have fun building it.

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Posted : 29/04/2014 1:09 am
Cathovisor
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The ECC82 seems fairly safe at the moment and prices are nothing like ECC83.

For a valve that was IIRC originally designed for use in TV timebases I'd hope that's where the dratted things stay! From memory,

ECC81 - first go at VHF amplifier/mixer-oscillator
ECC82 - TV timebase multivibrator
ECC83 - audio amplifier
ECC84 - not sure if this was the 6.3V version of the PCC84, the cascode RF amp for TV tuners
ECC85 - the de rigeur choice for the VHF tuner

...and wasn't the ECC88 intended for computers?

Just had a quick look at Langrex's stock list - they currently have over 5,000 6C4 and just under 5,000 EF91s in stock. Somehow, I don't think the world is about to run out just yet.

 
Posted : 29/04/2014 2:53 am
Dr Wobble
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Am I missing something here,the OP sais the radio was a complete flop,so why would you want to build it ?

Was briefly interested in this as its someones birthday soon and wanted something to buy for that someone/build with/from Molly,like a one valve radio. hope that makes sense. Andy.

Curiously curious

 
Posted : 29/04/2014 7:54 am
crustytv
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Am I missing something here,the OP sais the radio was a complete flop,so why would you want to build it ?

You got the wrong end of the Stick Andy, with regards to it being a complete flop. Going by examples of Roberts work and posts, I somehow seriously doubt anything he invests time in is ever a flop.

From my understanding the radio works fine, the "flop" was peoples lack of interest in building it or wanting the E-book. Robert offered his build document elsewhere and met with equal apathy, quite frankly I can see why he would give up, thankfully he did not and offered it here.

I think it is a great idea, a simple radio and superbly written document. This is why it will be a feature on the main website.

I'm sure Robert will be along shortly with a more detailed response.

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Posted : 29/04/2014 8:38 am
crustytv
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Roberts guide is now live on the main website under the "How to guides" ( right-hand menu ) called Build A Simple Radio

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Posted : 29/04/2014 10:15 am
Anonymous
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A very good write up and easy to understand, it should be an easy and fun project for anyone to build.
Nice one Robert.

Have you done a 1 valve amplifier project to drive a loudspeaker?

Mike

 
Posted : 29/04/2014 10:44 am
Terrykc
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Very interesting: a modern slant on an early style of radio production.

I can't say that I'm happy about the crocodile clip battery connections, though!

As an alternative to the EF91, why not use a DF9x type? One D cell lasts for a very long time and keeps the receiver independent of the mains. It would then resemble my first attempt at the one valve TRF I built nearly 60 years ago.

I'd been given an empty chassis, punched for octal valveholders, so used a 1N5 I got from an advert in PW and took advantage of the oversized chassis to strap the batteries neatly on the top. As in this design, I had a scrap 500ρF twin gang capacitor but the reaction control was a problem as I didn't have anything suitable and cash was in short supply!

The thing about the one-valve TRF is that there is a myriad of designs out there, all almost identical but never quite the same, and they all work! I found a circuit in a book in the Junior Library that suited my needs perfectly. Instead of the usual variable capacitor for reaction, it used a fixed cap in series with a pot - and I had plenty of those, scavenged from various scrap sets!

In those days, all designs were intended to be used with (expensive) high impedance headphones but, similar to this design, I used a scrap output transformer in conjunction with an ex WD low impedance earphone being sold cheaply by Duke's in Manor Park.

Like most people in those days, I cheated by building my set round the easily and cheaply available Repanco DRR2 coil ...

The performance was staggering - extremely sensitive, very selective - and the RC reaction control worked very well indeed!

... Have you done a 1 valve amplifier project to drive a loudspeaker?

You could borrow a bit from this, Mike!

The beauty of a circuit like this is that you can build it any way you want, change it to suit yourself or component availability (within reason!) and it will still work!

For example, instead of the current magnificent design, if you could find a stache of miniature solid dielectric 500ρF variable caps and a Repanco coil, it would fit comfortably on a 2oz tobacco tin!

When all else fails, read the instructions

 
Posted : 29/04/2014 11:52 am
Terrykc
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... Beginners might wonder why they can't see the filament glowing and wind things up a bit. Whoops! ...

If you can tell us how to do that with a single D cell (I envisaged it as being in a single cell holder) I'd be very interested ...

I suppose you could use the pentode section of a DAF9x valve instead - in a darkened room, at least, you can always see the extension of the filament that passes through the diode anode ...

When all else fails, read the instructions

 
Posted : 29/04/2014 12:04 pm
Anonymous
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Actually I would use generally available Mains valves able to work down to 12V HT of 12V or about 24V. See below.

See
http://www.junkbox.com/electronics/lowv ... ubes.shtml

Note an ECH83 is exactly a differently labelled ECH81. Proved beyond doubt.

I think Terry has told a greater truth here. It's not just about replicating the exact design, it's about the inspiration to experiment and get results from very simple circuits. The snag with using a DF9x battery valve is that they are now in relatively short supply. Beginners might wonder why they can't see the filament glowing and wind things up a bit. Whoops!

I wonder if a Russian rod pentode would work :aah

Of course they will. As Triodes, Pentodes and Tetrodes. Or two to replace a Heptode/octode.
Millions of them and 1p23b / 1j29b can be run off 2V instead of 2.4V to simulate any 2V valve.

The ECC82 of course will work down to 12 V with 0V or slightly positive grid as will ECH81 (ECH83 is same valve).

As an alternative to the EF91, why not use a DF9x type? One D cell lasts for a very long time and keeps the receiver independent of the mains.

Seriously bad idea. These are quite expensive enough already for replacements. Use 1j29b, 1j24b, 1j18b at 1/10th of cost and millions of them NOS from 1977 to 1991. The 1j24b is only 11mA filament. No valve holder needed. Solder flat between tag strips, or plug in to breadboard or use IC socket strips or veroboard.

Excellent research by Cathovisor on availability for the Community. Anecdotal accounts of what is on ebay or in our own stock isn't good enough. We need to create a list of common replacements for Battery, mains, Magic Eyes, Audio Power valves etc with data sheets to help people creating new projects. The temptation is always to use what is to hand.

You can run E series heater of a 6V Lead Acid as long as it's not on charge. (or of 5 x NiMH with low drop out regulator, that's actually nominally 6.75 if not on charge, not 7.5V).

Or a 6V + 6V transformer to give about 6.3 V off 240V for filament and rectify the 12V AC with doubler (windings in series 2 x diodes and 2 x capacitors, heaters have to be "floating" on either winding but if more than one they can be evenly shared between windings to allow smaller transformer) and for 25V to 30V HT (easy as only 2mA to 15mA needed). More than adequate for ECC82, ECH81 etc if grid bias is near 0V. Not sure about EF80. I will test.

I'll post a photo & schematic later of a test setup with transformer, PSU and socket so you can easily see what grid voltage for suitable Ia with 12V and 30V HT

 
Posted : 29/04/2014 12:40 pm
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