1 valve kit radio?

[fusewire]

Hi, I've just got a one-valve (3B7) radio called "Skyroma" looks like 60s possibly a kit? Does anyone have one? I'm looking for circuit.

Thanks,
Bob.

[Cobaltblue]

Hi Bob,

Its a very simple set so a circuit can be drawn out the coil looks like a Repanco DRR2 ( can't guarentee it and someone else may better recognise the coil) you can find some information on Repanco coils here: http://vintageradio.me.uk/info/repanco.htm. The 3B7 is an interesting choice looks like war surplus you can find info here http://www.radiomuseum.org/tubes/tube_3b7.html
Its a double triode. I think is a very nice little radio. I doubt those war surplus caps will be faulty. I would be very carefull with the valve I suspect its not common.
Good luck with getting it operational
Mike T

[fusewire]

Hi Mike,

It does look to me like a Repanco coil. It uses two dielectrics and some of the insulation spacers are breaking up and sound all crunchie when turned.

I think I should reverse engineer the wiring. I think maybe they are using one half of the valve because it is wired for one half of the filaments (1 fill).

Thanks for your info.

Regards,
Bob.

[kibble]

I have a set labelled "The Little Jewel Radio. Made by J ROBERTS" see http://www.radiomuseum.org/r/unknown_little_jewel.html

This set is the same as sets advertised as "Skyroma" in Practical Wireless during the 50's & sold by Concord Electronics of Brighton.

A similar circuit appeared in Practical Wireless July 1957 as a compact mains set. I have a scanned copy I can send you if you are interested.

Regards
Keith

[fusewire]

Hi Keith,

That's it. Exactly the same, copy cat was that legal?

I would like a copy of circuit, how would you send it, post or email? The valve in the one pictured has a bakelite base, mine's metal. Is your valve a 3B7?

Regards, Bob.

[kibble]

Having examined my set I've edited a similar diagram to match, hopefully I haven't made any mistakes. I found it easier to edit than draw a new diagram. The valve in my set is a 1G6.

The PW project used a 6SL7 as it is a mains set. The article is a bit large to past here, but if you pm me your email address I'll send you the article.

Regards
Keith

[David G4EBT]

On the face of things, the loctal-based 3B7 was an odd choice for a battery radio, given that the heater current at 1.4V is 220 mA, but they were good up to UHF, so more than up to the task, and I guess they were cheap at the time. (They’re not dear now – NOS Raytheon 3B7s are presently on offer at £7.00).

There’s a nice homebrew example of a 1-valve TRF using a 3B7 at this link and the circuit might interest you Bob:

http://merrijoysmusic.tripod.com/med.hamradio/id3.html

Most of the kits that abounded in the late 50s - early 60s, which featured in PW ads, used whatever cheap ex-war surplus stocks of valves and components they could get hold of, at a time when the country was awash with such stuff. The valves were chosen not because they afforded optimum performance or where the best for the job, but because there were shed-loads to be had at knock -down prices.

I built several of these various kits in my late teens, and on the whole, they performed well, but were greedy for batteries. In 1956 I built a little set advertised as ‘a personable portable radio at a down to earth price, giving world-wide reception from 10-100 Metres’ from RCS Products. It looked a bit like a walkie-talkie with a rod aerial. It used two ex-WD 954 pentode acorn valves, which - though they worked well - were most unsuited to the purpose. They had 6.3V heaters, and consumed 150mA each; whereas low current miniature B7G based valves as used extensively in portable valve radios of that era consumed only 50mA at most.

The anode current of the acorn valves used in that set was 150 mA - three times that of miniature B7G valves. The HT was from a hearing aid battery, which lasted abut ten hours, and the LT was from four C cells, which quickly ran down.

The famous ‘HAC’ (Heard All Continents) one-valver used a pre-WW2 HL23 battery valve, which had a 2-volt heater. Though the heater current was relatively low at 50mA, similar to a B7G valve, to drop the voltage from a twin cell 3-volt battery to the required 2 Volts necessitated the insertion of a resistor in the heater circuit to ‘lose’ 1 volt. Again, the choice of valve can only have been because being pre-war and obsolete, it was cheaper than the post-war 1.4V heater B7G valves. (Unless it was thought that a larger octal valve looked more ‘authentic’). HAC recommended a front cycle lamp twin-cell battery, type 800 for the LT.

I look back fondly on those days. With the passage of time, these sets have taken on a certain charm, particularly to those of us who grew up through that era and were impressed by adverts, which often promised far more than they delivered. They weren't as cheap as they may now seem - the basic 1-valve version of the RCS ‘personal portable radio’ that I built in 1956 cost me 30 shillings, which equates to £29.00 today. I think the upgrade to 2 valves cost me 7s6d – about £7.00 at today’s price. As an apprentice, that amounted in total to half a week’s wages.

Happy days!

[fusewire]

Hi Keith,

This will be fine, thanks. I wonder if this circuit would be ok to adopt using a 1D8GT valve?

I got mine working, it had a resistor shorting to a pin so I moved it away. It's very noisy and scratchy and those dielectrics aren't much good. An air-spaced cap for tuning would be better. I'm not sure whether to salvage the Repanco coil for something special and I wish someone would remanufacture these coils. They always seem to make loads of money when they come up for sale on eBay, especially the crystal set one.

Regards,
Bob.

[fusewire]

Hi Dave,

Thanks for your info. I too was in that era and I think I'm trying to relive the past. The 60s was the best time in my life and I'm not happy with all this modern electronic technology and strange digital airwaves.

Regards,
Bob.

[David G4EBT]

Just a small correction to my post No2 above. I described the 3B7 circuit to which I provided a link as a 1-valver. In fact it uses two valves - an AF pentode for audio amplification, as well as using both triode sections of the twin-triode 3B7.

There seems a definite upsurge in simple sets such as these, which are capable of impressive results.

David.

[HMV 1120]

I have a virtually identical set marked A.S. Charles Long, utilising a Mazda VT150, this time the coil is marked "Weyrad". Pictures are from forum member Richards posting here: https://www.vintage-radio.net/forum/showthread.php?t=62073&highlight=A.S.Charles+Long

The VT150 has an O/C filament, I've yet to find another.