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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 5th Jun 2021, 9:00 pm   #1
weanedontubes
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Default BULGIN. Transcoupler

Hello.
Does any one have any info on these, ie component make up and circuit.
Tks. David.
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Old 5th Jun 2021, 9:21 pm   #2
Ed_Dinning
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Default Re: BULGIN. Transcoupler

Hi David, possibly a form of resistance capacity coupling, which could incorporate a choke as well.
Radio books of the period may well have circuits of its innards.
Transformer coupling was popular as it gave some additional "gain"

Ed
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Old 8th Jun 2021, 3:47 pm   #3
weanedontubes
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Default Re: BULGIN. Transcoupler

Thanks for your reply Ed.
I think I may have answered my own question.
Seems at the 1932 Olympia show there were a few new innovations to improve the characteristics of the LF transformer stages. The Bulgin offering was one of these.
I found the following write ups in the magazines of the time. It pretty much sums up the situation.
Regards.
David.
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Old 8th Jun 2021, 6:27 pm   #4
emeritus
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Default Re: BULGIN. Transcoupler

The Transcoupler (Bulgin code L.F.10) appears in their 1936-7 catalogue, price now only 10/6d.

" This is the well-known fed-transformer unit, the first of its kind, incorporatng all the necessary resistances, condenser, etc. The latest and present model incorporates indestructable resistances of the Bulgin "Miniature" type. The "Transcoupler" replaces transformers of the straight-connected type, gives greater amplification, and better treble and bass response. The Transcoupler may follow any valve."

The catalogue provides no circuit diagram or other technical info.

Last edited by emeritus; 8th Jun 2021 at 6:28 pm. Reason: typos
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Old 8th Jun 2021, 6:43 pm   #5
Robert Gribnau
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Default Re: BULGIN. Transcoupler

See for a schematic page 222 of this Practical Mechanics of February 1934: https://worldradiohistory.com/UK/Pra...4-02-S-OCR.pdf
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Old 8th Jun 2021, 8:25 pm   #6
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Default Re: BULGIN. Transcoupler

A simple RC coupler with anode load, easily replaced by two resistors and a capacitor. Why build one when you could get the whole lot for 10x the price and impress your friends?
 
Old 8th Jun 2021, 9:44 pm   #7
weanedontubes
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Default Re: BULGIN. Transcoupler

Thanks for all your replies. The circuit diagram from Robert was just the ticket. Those FJ Camm magazines were all ways a good read for the money. You could buy a bunch for just pocket money back in the 50's.
I am posting the here the diagram from the Practical Mechanics magazine.
Regards.
David.
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Old 9th Jun 2021, 1:53 pm   #8
Ed_Dinning
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Default Re: BULGIN. Transcoupler

Hi Still has the transformer to give a bit of gain and possibly go open circuit with age, but now parallel fed so no DC in core and possibly a smaller core

Ed
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Old 9th Jun 2021, 5:09 pm   #9
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Default Re: BULGIN. Transcoupler

Ah, the transformer could be a lot smaller and better not having to cope with the standing current though it, I stand corrected.
 
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