ACORN 1 - the final version

[Variometer]

I have now laboriously made a new set of components for the final build. The veneered baseboard will be cut down to the correct size & the rough edges hidden behind front & back panels & alumnium sides. The brass strips will be polished, but the straight wiring can remain as it is (enamelled heavy guage copper wire).
Bob

[Variometer]

The aluminium side angle have now been fitted to the baseboard. The coil & valvholder are in position & all the brass strip wiring. The brass strip is no longer all "earth" connections. The right-angle on the top right hand corner will convey the HT to the primary of the output transformer, whilst the angled piece beneath the valveholder will connect the anode to the other output transformer primary terminal.
Bob

[Buzzkf9cm]

Hi Bob,

Brilliant concept and design. I think your layout is very original.
Great work Bob.

73 de Gary,KF9CM

[Variometer]

Hi Gary,
Thanks. I completed it half an hour ago. Plugged in LT & valve didn't light, despiate heater being OK. Went down to shed in pouring rain for another. This time it did light & on applying HT of 90V all was well & it worked as good as the prototype. Closer inspection of original valve found that it was cracked round a pin, so air had got in!
Sometimes I feel this type of radio is a combination of woodwork, light engineering & radio as well! Lots of nuts & bolts. Made the brass knurled nuts myself. Polished up the brass wiring strips, veneered the baseboard. Front & back panels are glossy black acrylic. Sides are aluminium.
Bob

[Sideband]

Excellent work Bob . It's really like a trip back to the good old days of the hobby. Well done.



Rich.

[chipp1968]

Very smart , good work

[dave walsh]

Really excellent and interesting further version Bob! Worth a trip to the shed in the rain! It's been baking hot in Sussex so will stay put for a while. Dave W

[murphyv310]

Hello.
Cracking job! Really nice and the way it should be done, award yourself 10 points.
Trevor

[boiss]

Hi Bob
Super job! The brass strips are an excellent idea fixed to the base plate.
It's given me a few ideas for my next toy!!
Mike.

[petervk2mlg]

Brass strips are a great idea - rather like the way the old Telefunken Arcolotte was built in 1929/30- a very early kind of pcb!
Peter

[Variometer]

Thanks, I got a big box of brass strips from a car boot sale for next to nothing some time ago. They are stuck down with double-sided tape, but the joints are soldered & nuts & bolts put through in the middle of the longer lengths. It wont matter about eventualy failure of double-sided tape because the completed wiring holds everything firm.
Bob

[humphrey]

May I have a link to the original thread?

[Variometer]

Hi Humphrey,

The first part of this build can be found here:-

https://www.vintage-radio.net/forum/...ad.php?t=29295

entitled "The Paint Tin Acorn one prototype".

Details of the paint tin tuning coil are in thread

Tuning coil made from paint tin

Bob

[Dave757]

Hi

I wonder if anyone has the circuit for the Acorn Valve receiver?

Most of it is clear from the pics, but it would be nice to have the
coil details etc.

Kind regards

Dave

[David G4EBT]

Originally Posted by Dave757

Hi

I wonder if anyone has the circuit for the Acorn Valve receiver?

Most of it is clear from the pics, but it would be nice to have the coil details etc.

Dave

Bob - 'Variometer' will have - he designed it, and I'm sure he'll be only too pleased to note your interest and would probably be happy to send you the circuit if you drop him a PM. (He regularly checks into the forum, most recently on 10 July). He recently wrote an e-book on how to make your own one valve receiver using either an HL2 triode or an EF91 pentode entitled: 'Vintage Radio & Electronics For The Home Constructor - A One Valve Battery Receiver'.

The 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 from six 9 Volt batteries connected in series to make up the required 54 Volts for the H.T supply. Two versions of the circuit are described - the first uses a very old HL2 4-pin triode valve - the second version make use of the far more common EF91 pentode valve in place of the HL2.

However, in March this year on the forum, Bob reported that (to use his words):

"This e-book was a complete and utter failure and has now been abandoned (by me). However, I will be happy to e-mail it to anyone free of charge if they send me their e-mail address in a PM".

See post #22 at this thread:

https://www.vintage-radio.net/forum/...784#post669784

Hope that helps a bit.

[Dave757]

Many thanks David

Kind regards

Dave G0ELJ

[Variometer]

Here is the circuit with component values. L1, L2 and L3 are small RF chokes 47uH each, inside the coil can. The coil connection labelled "can" is just soldered to the can on the inside. The connection just goes to earth. If the reaction does not work, just reverse the connections to coil 4 and 5!
Bob

[David G4EBT]

Nice to see this thread re-awakened! I recall being very impressed with the original back in 2008 and thought that using a Humbrol tinlet for the coil screening can was a nifty idea, as was the use of three 47uH chokes for the tuning coil to save coil winding - often the biggest hurdle for homebrew sets.

I'm awaiting delivery of some 958-A acorn triodes (1.25V heater version of the Acorn series, rather than the more usual 6.3V). It might just fire my interest, but that said, I still have all the bits in a box, including coils that I wound, for a Short Wave Mag Acorn 3-valver, still waiting to be assembled since goodness knows when! Trouble is I've been retired for 20 years and it's a full time job with long hours, so I get little spare time for projects, and the 'do list' gets longer with each passing week.

[Variometer]

I wrote the Acorn 3 article in the Short Wave mag years ago, although the AF amp was not an acorn. It worked well, but if I remember correctly, they forgot to put the values on the capacitors on my RF tuning switch and also missed a dot (wires joined) from the circuit that would have prevented it working.
Nice to see interest reviving in this sort of thing. I have not done any radio for some months now as interest in "homebrew" seemed to be at an all time low.
Bob

[David G4EBT]

I've just dug the SWM article out Bob, and the one that I'm referring to was in fact by an author called Brian Adkinson and used three 945 Acorns. The article was spread over four issues of SWM from October 1992 to Jan 1993. I got all the bits together in 2003 and they're in hibernation waiting for me to awaken them from their slumbers! A fellow forum member who is a prolific home-brewer ('Peter') built one in very short order back then when I passed him the article.

One day perhaps...?

Sad to say that you're right about home-brewing - it mirrors other hobbies - model engineering, woodturning, aero-modelling, model boats - you name it. Many people have a passing interest in such activities, but are passive rather than active participants. They may buy a magazine or two from time to time, but that's as far as it goes.