I have a Lewbury Lectric radio that has seen better days I have to try and restore for a lovely lady. Upon seeing it I said no but she begged me to have a go.

Valve line up 80 , 59 , 57 any clues to a circuit diagram or any info would be greatly appreciated,

Basically I have a chassis I have to populate with components.

Cheers
Vic

80 rectifier; 59 output; 57 (6J7). Are they all of the valves? If it's a screen grid (autodyne) I think we need a couple of 57's.

Unless it is some form of TRF

Early thirties. Might be an idea to get photos of top & pan inside.

Marc

If it's of any assistance, we discussed Lewbury Lectric last year here:

http://vintage-radio.com.au/default.asp?f=1&th=609&offset=1.

Hello Marc,

yes it only has three valves and very little underneath the chassis.

It looks complete but has been played with. Top is all original.

Cheers
Vic

OK! TRF most likely. Need to see what coils it has. I have seen sets like this. Astor GN (Football was one) Cult following horror set otherwise. It did have detector diodes in the tube.

Yours will likely use the 57 as a plate detector and a pentode is the best using "top bend detection" as that overall will give the best gain to drive the OP tube. There is also the possibility that the set may be reflexed to help reduce the distortion resulting from this type of detection.

I do not see it having a lot of components. The 57's cathode resistor may be of a high value and have both a 25μF electrolytic and a mica cap across it.

Such things can be reverse engineered, if we cannot find a circuit. PIB but I have had to do it. Ten valve superhet with WECO (Trench) valves was fun (sic).

Marc

Here are a couple of typical early 1930's 3 valve radio circuits. These ones use valve types 57, 2A5 (2.5 volt version of a 42 & 6F6) and 80.

Hi Marc,

Cheers
Vic

Note the incorrect nomenclature for the 57 in the second drawing, also note the cathode resistor for 2A5 is virtually back bias for the 57.

Pictures uploaded.

Looks like one of the simplest circuits for a three valver I've seen. I might even try and build one later in the year if time permits.

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A valve a day keeps the transistor away...

Pretty obvious that someone has has a go at this before.

Electrolytic's will likely have a date but the tin can on top is likely a double cap and paper. The resistor & I suspect cap in the RF can do not look original. For 57 2Meg is reasonable on the grid It may have a cathode resistor of 2200R (250V B+)

It is made for an electrodynamic speaker. Field can be subbed with a resistor and the second cap lifted a little to not exceed 32 μF (10 + 22) 500V? With electrolytics instead of paper I would put a 0.047 across the second filter.

We need to know Secondary AC to predict B+ That can be done Tubes Out. if not marked, but you may need to rewire mains side to do it. Do not measure plate to plate (80 small pins) unless the meter is capable of withstanding more than a KV. Measure plate to ground(CT) (chassis)

Coupling transformer (doubt it a choke) will need checking, notorious for failing still gettable new. and that one is not original I'll bet.

Your choice of a speaker transformer inside pan 6K careful with wiring if you put it on the speaker.

Looks fairly simple. You could reverse engineer easily. I do things like that.

Marc

Thanks Marc,

Armed with this info I will have a go at it , Simple it may be but I am not used to doing old radios like this.

Cheers
Vic

The last bod left that a bit messy. I do not like the position of the rectangular block cap (cathode bypass?) it could be closer to the valve.

The electrolytics look odd in the photo as if the positives are both joined and that is a negative on the CT? Watch that, the field may have been in the earth and that gets a lot of Americans into strife.

If the positives are together & on a large (filament) pin, fair bet that is how it is One cap negative (lowest & first) on CT the other ground (chassis). 80 small pins, plates; Big filaments

I need to see four wires on the grey transformer for it to be one, otherwise it may be a choke. It may look a lot tidier with the electrolytic's and the block cap on a tag strip, or between two. Using a bolt on the gang in the centre area.

The wetless caps will likely have to go. Cloth wire is available to get rid of that green plastic (vanity).

Make a point of checking all of the resistors and the best way I have found to leakage test Mica's As 57 grid one does not look original, is with an insulation tester, (Altronics?) with one end of the cap out of circuit. It will also test the non polarised "Wetless" but normally papers leak like a sieve and one does not bother.

If you are careful, I see no real issues. I would still be tempted to draw it. much simpler than a 10 tube "Trench" valve superhet that I reverse engineered.

QUOTE: Looks like one of the simplest circuits for a three valver I've seen.

Looks like a superregenitive radio. The RF stage is rigged up to almost go into oscillation, thus creating gain. One of the pots controls this, go too far and you'll get squeals. Back off on it.

See http://en.wikipedia.org/wiki/Regenerative_circuit.

Hi Marc,

Will have a look at it after the weekend and answer items you have mentioned.

Cheers
Vic

Good morning Vic,

I am following your plight of the Lewbury with great interest as I have the Lewbury 5 valve superhet referred to in the above string.

Unfortunately I think you will have to reverse engineer and draw out the circuit diagram as found, this is what I eventually had to do with mine. Information from members on this site was most helpful but but the Lewbury circuit proved to be different to circuits that were suggested. Mine is now fully restored and working and was well worth the effort, I hope that you will be able to restore yours as these two sets would appear to be the only ones in existence. It would be of interest if you have any information on the history of your set as the Lewbury Lectric brand is still very much an enigma.

My regards to you and all the others that so kindly helped me with my research last year, Mike.