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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 23rd Aug 2019, 10:00 am   #1
G0HFCFrank
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Default Roberts RMB Wavechange

Hi Folks,
The previous opponent of this Roberts RMB removed all the wires from the wave change switch and created the rats nest pictured. Looking at the circuit, the MW aerial coil L1 is the frame aerial and has four wires, black red yellow and green. I assume these correspond to connectors a b c & f on the diagram. The black wire is connected to chassis, yellow to C34 (tuning cap) and red and green jointed together and connected to the MW aerial trimmer C32.
I intend to repair or replace the 4 pole 3 way waveband switch and rewire back to original. Trouble is I don't know where the red green and yellow wires should go as I don't know which is which. If some kind soul with the same receiver could identify them for me I would be most grateful.

Frank C.
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Old 23rd Aug 2019, 3:24 pm   #2
GeoffK
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Default Re: Roberts RMB Wavechange

The red arrows show the 4 poles of each three way switch bank.

With switch in position S1 this is for MW section.
(Bank 1 aerial pole) S1 switched to L1 (MW frame aerial) inner, S4 (bank 2 pole from C4 aerial tuner & C5) to other (outer) side L1 top & trimmer C1.

S7 (bank 3) (from C8 & C9 osc tuner) to S7 (L9 osc pri) S10 (bank 4) (L12 osc sec & second grid (osc anode) V1

Repeat for other two switch positions.

Black would be going to common of trimmers C1 C2 C3 and C13 C14 C15 (C12) in osc section.
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Old 23rd Aug 2019, 5:46 pm   #3
ms660
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Default Re: Roberts RMB Wavechange

So far as I can make out....

Red (d) connects to S1, 2 & 3's wiper.

Green (b) connects to S2.

Yellow (a) connects to S5.

Black (c) connects to chassis.

Based on the Trader sheet schematic and switch drawing and a photo in the GVR forums gallery.

Lawrence.
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Old 24th Aug 2019, 9:04 pm   #4
G0HFCFrank
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Default Re: Roberts RMB Wavechange

Thanks Guys,

Geoff your pic of the front end is different from Trader Sheet 1037 and easier to read; Lawrence, thanks for the colour identification, it makes things a lot easier. Not much spare time this next week but watch this space!

Frank.
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