AC Civilian Receiver

[Joe]

I bagged this last night:-

   

It's already obvious that it's going to need a 'new' speaker. What I was wondering is if an 8Ω one would do if it had a resistor connected across it or what about two in parallel? There's an element of cart before horse in this as I haven't got it yet and it'll have to wait its turn when I do. At least it's not energised or anything odd.

Where the Dickens I'm going to put it don't know!

- Joe

[Aerodyne]

I'm a little surprised by the chickenhead knob top centre of the scale. This must be a mod by someone. Even the relative few that were built with medium and long wave coverage didn't have a control there - the third knob was fitted central to the existing two in the lower front of the cabinet.
As far as the loudspeaker goes, I guess there's be no real harm in trying an 8 ohm unit but the mismatch is probably going to cause distortion and low volume. Wiring a resistor across the speech coil won't help the problem IMO. Ideally you need a correct unit. With a bit of luck you might be able to repair the existing cone or even recone from another unit.
Nice little sets to work on, but watch out for the unusual demodulation method.
-Tony
Quick edit: a sdecond look shows the folly of my suggestion re cone repair. You can't repair what ain't there!

[Joe]

Cheers, Tony.

I regard that large chicken-head knob as a nice bonus and am pleased that the fixed part of the scale is still there at least.

The speaker is beyond hope but luckily this is just a 'bog standard' one. It's more of a medium term project so I expect something will turn up and it can borrow the one out of my homicidal Ekco for a while - it'll teach that one to mind its manners.

I'll know more when I actually get hold of it.

- Joe

[OldTickTock]

Hi Joe,

Once you get it let me know what's what. I had a rummage through my stock and found four vintage 8" speakers in my spares three are 3 OHMS, one the Celestion is 12 OHMS. I'm hoping that's the standard size they used in the wartime utility set

I hooked them all up as Extn's to the workshop radio and they are fine.

If it's the right size I think the TrueVox will be the most in keeping, it's still got the dust sack on it. In case you were not aware these sacks are left in situ when the speaker is placed in the cabinet as dust protection. It came out of a 1936 Philips 838U.


Chris

[Joe]

Thanks, Chris. Let's just hope we're not tempting Fate!

- Joe

[Yorkie]

I think that the most likely reason that chicken head knob will have been fitted to the tuning cap shaft, which is in the centre of the moving dial cursor disc, will have been due to the tuning drive string having snapped. There are only two knobs on the front of the set - the left hand being the volume/on-off switch, the right hand being the tuning control, coupled to the tuning cap with a short drive cord. I don't know why anyone would fit a chicken head knob (assuming it's the original tuning cap, as it most likely is - why would it not be?) because there's a slot in the shaft of the tuning cap at the front so that it can be turned with a screwdriver if need be.

I've attached some pics of mine, which I mentioned to Joe that I bought cheaply at a Radio Rally 'a few years ago'. It was actually 1985, so I've had it 26 years - almost half of its life! It must have been in a bit of a state when I got it, because I note that I renewed most of the wiring, including opening up the IFTs to fit new wires, but I see a couple of waxies that I didn't change. I recall that I had to respray the dial and apply new lettering, with Letraset rub-down transfers, which matched the font originally used, then I oversprayed the dial with a few light coats of lacquer. A heavy coat will cause the lettering to come loose and float off. Trust me on that! The speaker cloth had rotted, so I replaced it with the nerest thing I could find that didn't look too out of place.

What I find odd about these radios is that they were allegedly designed in the interests of economy, yet they're very heavy, and have a really hefty mains transformer, whereas if we were given a brief to build an 'economy set' we'd surely have used AC/DC techniques, or a small auto-transformer. The chassis is heavy gauge steel, the speaker metalwork is very substantial, and the IF cans too are heavy gauge steel. Yet while glass was probably the most plentiful resource available, and not even recycled back then, apart from milk bottles and pop bottles, there's no glass in the dial, which is only about 2.5" x 3.5". Sure, it uses a 'Westector' detector, which some may argue saved on a valve, but it didn't really, as there were plenty of valves about which incoprorated a diode in the AF amp or IF amp valve. EBL31's (as used in the Ekco A22) are double diode pentodes which take care of th AF amp, detector and AGC. Scarce now - but not then.

In short, this set looks like what it is - a radio designed by a committee, to be made to a standard design by almost 30 manufactuers, with an austere utilitarian appearance to convey the illusion of wartime economy. A bit late in the day as the war was coming to an end by the time it went into production, and any half decent manufacturer - Ekco for example, could have designed a far more economical set.

Furthermore, confining the set to AC only, not only made it more cosly and wasteful in materials, it also failed to serve the needs of DC only customers, of whom there were millions back then. Our house in Nottingham wasn't convered to AC until 1959.

It will be an interesting restoration Joe - hopefully a speaker will turn up from a scrapper from Chris or another forum member, as I'm sure that one will. At BVWS events, often they have batches of valve and transistor radios they offer for £2.00 each from 'estate sales', though I know it's difficult to get to such events for many forum members. At the last Golborne event, Mike Braker had many portable radios at £2.00 each - I picked up a shabby TR82C and Roberts R200, both of which work, and simply need tidying up.

As to chicken head knobs, I've seen them advertised at ludicrously hight prices - £3.00 each, but asd I mentioned recently, Peter at 'JABDOG' sells them at 10 for £3.00 or 25 for £7.00.

I've attached a few pics of mine.

Hope that's of interest.

David

[Joe]

That's a fantastic restoration, David, though I'd expect nothing less!

Mine should be here today so it'll be interesting to see just what's what.

[Aerodyne]

The Westector may have been used due to the shortage of a suitable double-diode triode or pentode valve; note that the AGC circuit is odd to say the least, as the diode for this (clamp diode) is formed by V2 suppressor grid and cathode, with no control grid coupling cap but rather with direct connection to the secondary of the aerial input transformer, the bottom end of which being supplied with AGC voltage and decoupled by a 0.005uF cap. An unusual arrangement and one which could cause some head scratching in the case of 'no signals'. Although the Trader sheet is representative there are variations in form and connection of these front-end components from maker to maker, not to mention 'modifications' carried out by 'fixers' desperate to keep sets working through component shortages.

I see your point, David, about the cost anomalies. The transformer alone makes up a sizeable proportion of the chassis cost, I would have thought. It seems as if the set was quite deliberately 'styled down' to look economy in form, a political statement of the notion of belt-tightening austerity that was extant at the time. The cabinet is a good example of something cut down to the basic: made in rough, poor quality timber with just the two fluted verticals in a basic hardwood, it looks like a secondary school woodwork project!

As far as that chicken-head knob goes, the spindle surely must hsave been extended in some way to accept the knob? It does seem like a spot of overkill. The cord is a simple replacement job, after all.
Joe, the main point about a replacement loudspeaker apart from impedance and cone size is the way of fixing it. I'd guess you need one with a standard rim with four fixing holes. The Philips one mentioned by Chris is likely to have no such flattened rim, being fixed by clips or pressure plates. If you can, go for the standard type. Watch for woodworm in that softwood, too.

Interesting sets, these, and capable of surprisingly good performance.

-Tony

[OldTickTock]

Hi Just to clarify the ex Philips Truvox speaker does have a flat rim and does have fixing holes and thus would fit fine.

Chris

[Tedzed1]

Hello David, what a wonderful restoration, I'm envious

How did you refurbish the tuning scale to such a high standard?