Detrola 438 Range receiver manual/schematic - UK Vintage Radio Repair and Restoration Discussion Forum

Hans PE1KWH · 24th Sep 2021, 9:29 am

I am looking for the manual/schematic for the Detrola 438 BC-1206 range receiver.
I have got the grey version which does work but i believe the output can be wired for low and high impedance headphones.

There should be a manual describing all versions : T.O. 16-40BC1206-2
but can't find it online.

turretslug · 24th Sep 2021, 11:13 am

I'm sure I did once find a circuit diagram for the Detrola version online, it's easy to find the circuit etc. for the Setchell-Carlson model but whilst they are functionally similar, they use different tube types with detail circuitry differences (also slightly different IF frequencies).

Good luck with it, it's an interesting little radio with its use of 28V aircraft supply for HT. Very compact!

Hans PE1KWH · 24th Sep 2021, 6:54 pm

Yes it is the smallest BC receiver part i know from the ww2 era.

It works but uses 2 tubes in the end stage as opposite to the single ended output used in the Setchell ( i do have one of them too ).

Nice about those radios is the 28 V supply AND you can still use them where they are designed for, listening to beacons although not much last these days.

Terry295 · 24th Sep 2021, 8:19 pm

Hi Hans

Hope these are of some assistance. The values in red on the redrawn circuit are highlighted as they seem very high but that is what the original circuit say they are?

Wonderful little set, still hear some of the aeronautical NDBs from around the country!

Cheers Terry C (ZL4TC)

Terry295 · 24th Sep 2021, 8:21 pm

Apologies omitted to attach files, here they are

turretslug · 24th Sep 2021, 10:35 pm

Quote:

Originally Posted by Terry295

The values in red on the redrawn circuit are highlighted as they seem very high but that is what the original circuit say they are?

There was a convention with some older circuit diagrams to use "M" as the 1,000x multiplier, presumably from the Latin "mille" or some such root. Things make much more sense when this is borne in mind, e.g. a 40k local oscillator grid resistor, and 1k HT decouplers.

Hans PE1KWH · 25th Sep 2021, 7:07 pm

Great,

Thanks Terry,
This makes me happy.

The radio works but i like to see if i can switch it to low impedance headphones.
I found the wire studs but now understand how to change it.

Have a great weekend.

24th Sep 2021, 9:29 am	#1
Hans PE1KWH Triode Join Date: Jul 2016 Location: Hilversum, Netherlands Posts: 33	Detrola 438 Range receiver manual/schematic I am looking for the manual/schematic for the Detrola 438 BC-1206 range receiver. I have got the grey version which does work but i believe the output can be wired for low and high impedance headphones. There should be a manual describing all versions : T.O. 16-40BC1206-2 but can't find it online.

24th Sep 2021, 11:13 am	#2
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,400	Re: Detrola 438 Range receiver manual/schematic I'm sure I did once find a circuit diagram for the Detrola version online, it's easy to find the circuit etc. for the Setchell-Carlson model but whilst they are functionally similar, they use different tube types with detail circuitry differences (also slightly different IF frequencies). Good luck with it, it's an interesting little radio with its use of 28V aircraft supply for HT. Very compact!

24th Sep 2021, 6:54 pm	#3
Hans PE1KWH Triode Join Date: Jul 2016 Location: Hilversum, Netherlands Posts: 33	Re: Detrola 438 Range receiver manual/schematic Yes it is the smallest BC receiver part i know from the ww2 era. It works but uses 2 tubes in the end stage as opposite to the single ended output used in the Setchell ( i do have one of them too ). Nice about those radios is the 28 V supply AND you can still use them where they are designed for, listening to beacons although not much last these days.

24th Sep 2021, 8:19 pm	#4
Terry295 Tetrode Join Date: Nov 2009 Location: Christchurch, New Zealand Posts: 64	Re: Detrola 438 Range receiver manual/schematic Hi Hans Hope these are of some assistance. The values in red on the redrawn circuit are highlighted as they seem very high but that is what the original circuit say they are? Wonderful little set, still hear some of the aeronautical NDBs from around the country! Cheers Terry C (ZL4TC)

25th Sep 2021, 7:07 pm	#7
Hans PE1KWH Triode Join Date: Jul 2016 Location: Hilversum, Netherlands Posts: 33	Re: Detrola 438 Range receiver manual/schematic Great, Thanks Terry, This makes me happy. The radio works but i like to see if i can switch it to low impedance headphones. I found the wire studs but now understand how to change it. Have a great weekend.