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Old 3rd Mar 2013, 1:12 pm   #1
Goodfellas
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Default "Universal" valve radio

Hello,

I have a bakelite radio with the brand name "Universal". It works well enough although the reception is very dependant on the angle the radio is at. At the back of the radio there is an aerial wound around the back panel but also a length of loose wire. Can anyone tell me if this is how the aerial is supposed to be? Or can I remove the loose wire?

Also, I'd love to know when this was made, I'm guessing the 1940's.

And was it a budget radio? (Is is a very simple radio.)

Thanks,

Oliver.
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Old 3rd Mar 2013, 2:20 pm   #2
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Default Re: "Universal" valve radio

Oliver,

The dial markings are a clue to the date of your radio. In this case "BBC 3" appears a two points of the medium wave scale - representing the Third Programme, which began in 1946 and became Radio Three in 1967.

If the set is not a well-known one, the valve line-up gives some indication of the design philosophy and the valve types will also relate to the time the set was made. Octal, Mazda Octal and similar sized valves were used up until the early 1950s and began to be replaced by types with B7G, B8A and B9A bases from the late 1940s. More exact dating can be set by codes on some components, especially electrolytic capacitors which usually are marked with the date of manufacture. Obviously this depends on their being the originals.

In default of a service sheet, a circuit diagram or a sales brochure, photographs of the inside would help with dating.

As you are fairly new to the Forum, I hope you won't mind being reminded that any radio intended for AC or DC mains will have a live chassis and needs careful safety precautions when working on it to prevent possibly fatal shocks. You radio is very likely to be "Universal" in this respect too.

PMM
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Old 3rd Mar 2013, 2:42 pm   #3
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Default Re: "Universal" valve radio

Hi PMM, thanks for the info. I'll take a look inside and might post a couple of pictures. I'll take care not to be zapped by it

Any clues as to the aerial setup I mentioned?
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Old 3rd Mar 2013, 3:01 pm   #4
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Default Re: "Universal" valve radio

Hi Oliver,

Not exactly the same as, but very similar to, this Portadyne.

Colin M
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Old 3rd Mar 2013, 7:37 pm   #5
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Default Re: "Universal" valve radio

There have been a few of these on the forum over the years. Another possibility is that it's a kit set. The cabinet is, I belive, a Pilot Little Maestro-style one, which was marketed by surplus outlets well into the 1960s for amateurs to build their own sets into.

N.
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Old 3rd Mar 2013, 8:10 pm   #6
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Default Re: "Universal" valve radio

With that case it shouts 'kit' to me. Goodness knows who was the vendor, but the apparent direct tuning drive is somewhat unusual. Does it use Octal or minature valves?
I had one with direct drive to the tuning capacitor, which was a seriously cut down short superhet & had minature 8 pin valves. Terrible performance.
Get that back off & let's see what she looks like inside.
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Old 3rd Mar 2013, 10:52 pm   #7
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Default Re: "Universal" valve radio

Tuning mine is not much fun since it needs very careful tweaking to get a station tuned just right! The radio's been working well all weekend, the output is loud (on some stations), although the sound is a little distorted so maybe it's due some renevation work.

I just looked at "Pilot Little Maestro" on Google images and yes the case is the same, although they appear to use the traditional (and better) method of turning the tuning capacitor!

I'll post pics of the valves soon.

By the way, I brushed my hand past the end of the aerial wire and got a tingle. I used a mains electrical test screwdriver (the sort with a neon bulb inside) and it glowed dimly when I touched the aerial... is this dodgy?
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Old 3rd Mar 2013, 11:13 pm   #8
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Default Re: "Universal" valve radio

The tingle and the distortion could both point to electrically-leaky paper capacitors, which you should change before using the set any more. Ask if you need more advice.

Good luck,

Nick.
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Old 3rd Mar 2013, 11:15 pm   #9
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Default Re: "Universal" valve radio

The case can be found used in the "Transportable A.C. Superhet", page 617 of November 1962 Practical Wireless.
Seems like a kit or small production run using surplus parts.
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Old 4th Mar 2013, 11:05 am   #10
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Default Re: "Universal" valve radio

It must be a kit set. There is a point to be made about the case: 'Little Maestro style' was the term used by one contributor to this thread and that's correct - although the case looks at first glance identical, there are subtle differences, the most obvious ones being the shape of the right-hand ribbed pillar. On the 'real' LM case this column of false louves is slightly broader and the front edge of the louvres carries a distinct flat, whereas with the'false' LM, the column appears simply rounded and of very slightly less width. Also noticeable is the flatness of the moulding above the LS grille louvres, where with the LM original there is a distinct slope downwards.

This begs the question: if the original (and costly) moulds were NOT used, why make such a close replica of the case? Was the original mould modified in some way? Did Pilot sell the rights to the design? Was the wooden version (or one of them) of this constructor's case identical to the LM wooden case?

I know - I need to get out more...
Tony
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Old 4th Mar 2013, 10:30 pm   #11
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Default Re: "Universal" valve radio

Thanks for all who have confirmed it as a kit, definitely looks like one. I don't mind though, I like its style and it's nice and small compared to my other larger valve radios.

I wonder if the mould they used needed fixing, hence the little differences noticed by Aerodyne.

As promised, attached are some pictures of the chassis.
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Old 4th Mar 2013, 10:34 pm   #12
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Default Re: "Universal" valve radio

Not much mystery regarding the 'guts' of this set. A 3 valve TRF with a metal rectifier.
The earlier ones used military surplus components. The fact you have had a 'tickle' from the aerial wire is alarming. Normally there should be a coupling capacitor between the serial coil & the wire aerial. This should be a low value mica capacitor. Those should not fail, but any other kind that are present ought to be regarded as suspect. Any waxed paper capacitor ought to be replaced without any prior notion of testing them. There is one location where a leaky capacitor can wreak havoc. It is the coupling capacitor to the first grid of the audio output valve. It is referred to as "That Capacitor". So notorious is it that it ought to be the first component to be changed.
Alright.. I know I am drifitng off topic. Our new friend needs to know these things.

Normally the tuning ought to be driven by a cord between a shaft & a far larger pulley attached to the tuning capacitor to give a reduction. Why the convenient reduction drive was dispensed with puzzles me. Maybe it just wasn't necessary with far fewer stations on the air then?
What are the valve types?
If that metal rectifier dies it will whiff like a old-fashioned privvy. The HT should be around 200V, as it is derived from the mains & the voltage drop across the rectifier is around 50V.
the rest of the Forum can advise on choosing a diode & resistor combo to keep the HT voltage from rising too high.
The audio distortion could be down to the leaky grid-coupler capacitor. Find it & change it!

Last edited by Neil Purling; 4th Mar 2013 at 10:43 pm.
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Old 5th Mar 2013, 12:44 am   #13
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Default Re: "Universal" valve radio

Quote:
Originally Posted by Neil Purling View Post
Normally the tuning ought to be driven by a cord between a shaft & a far larger pulley attached to the tuning capacitor to give a reduction. Why the convenient reduction drive was dispensed with puzzles me. Maybe it just wasn't necessary with far fewer stations on the air then?
Cheapness, pure and simple!
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Old 5th Mar 2013, 3:45 pm   #14
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Default Re: "Universal" valve radio

There's one good thing to get out of all this, TRF's have only a handful of bits to check/replace.
I somehow had a feeling it was a TRF.
Oliver, when this set's overhauled & working, don't expect it to perform as good as a super-het, TRF's seem to need a massive aerial before they perform.
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Old 5th Mar 2013, 8:35 pm   #15
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Default Re: "Universal" valve radio

Glowing bits commented
Quote:
when this set's overhauled & working, don't expect it to perform as good as a super-het, TRF's seem to need a massive aerial before they perform
Agreed, at least a reasonably efficient aerial...AND EARTH, which in this case could be a problem as it seems likely to be a live-chassis model, judging by the photos, because I see what looks like an output transformer (but could be a heater transformer) and a still smaller wound component, either a transformer or choke. None of which are likely to provide full chassis isolation, which might explain the tingle from the aerial lead - assuming the isolating cap is either absent or shorted. DON'T earth the chassis. You should get local station reception on a few feet of wire or run a much longer lead outside, high as you can and away from walls for most of the length.
Tony
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Old 5th Mar 2013, 9:46 pm   #16
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Default Re: "Universal" valve radio

Quote:
Originally Posted by Aerodyne View Post
I see what looks like an output transformer (but could be a heater transformer) and a still smaller wound component, either a transformer or choke.
Tony
I reckon the larger one is a heater transformer and the smaller one is output. Looks like a new blue wire is soldered to the heater transformer which might suggest a replacement mains lead. I hope the neutral is wired to chassis....



Rich
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Old 24th Aug 2013, 4:34 pm   #17
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Default Re: "Universal" valve radio

Well I finally took the chassis out of the case and can give some more info about this radio. It still looks like a project radio (or built from a kit), there are no brand markings or numbers inside.

There are two Brimar/BVA 6U7G valves. The third valve is hard to identify, one of the numbers is badly printed, it says:-

H^A CV1032 KB/T

Note: It might say CV1932 instead of CV1032, I've attached a picture.
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Old 24th Aug 2013, 5:05 pm   #18
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Default Re: "Universal" valve radio

CV1932 looks like a match to your picture- it's a triode equivalent to 6J5G or L63. It doesn't make a lot of sense with a couple of RF pentodes, though.

http://www.r-type.org/exhib/aaa0665.htm

6U7G is a vari mu pentode.

http://www.r-type.org/exhib/aaa0665.htm

CV1032 is an output valve of sorts, but it's a battery double triode which hardly sounds right either.

http://www.r-type.org/static/webcv03.htm

Is one of the pentodes doing duty as the output valve? Not impossible- it would be good for maybe a watt of audio.
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Old 24th Aug 2013, 5:36 pm   #19
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Default Re: "Universal" valve radio

I agree actually, after another google images search, it is a CV1932.

I'm alsmost afraid to ask this (and in my defence, I do have an electronics background, but not in valves!), but does this radio lack a valve (or solid state) rectifier? Please see the picture in my previous post.
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Old 24th Aug 2013, 6:21 pm   #20
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Default Re: "Universal" valve radio

Quote:
Originally Posted by Goodfella View Post
I agree actually, after another google images search, it is a CV1932.

I'm alsmost afraid to ask this (and in my defence, I do have an electronics background, but not in valves!), but does this radio lack a valve (or solid state) rectifier? Please see the picture in my previous post.
There is a device like a stack of washers threaded on a rod by the side of the loudspeaker, this is the rectifier. Neil mentions it in posting # 12.

Tony
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