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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 25th Aug 2018, 12:44 pm   #1
G4YVM David
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Default WS19 set audio pick up...

Can I connect a speaker / phones to the pins of a 19 set and listen to the audio without going through the control box? I ask because a friends 19 set is with me and I was trying to see whether I could listen to it. It has no control box and I am not sure of the pins for audio. I did find one with a rather unstable 12v Dc on it. Clearly that's not the one, but I was just intrigued...

D
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Old 26th Aug 2018, 7:54 am   #2
M0SOE_Bruce
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Default Re: WS19 set audio pick up...

The "A" set audio output is pin 4 of PL2A. You can connect a speaker between it and ground. The output impedance is 100R as it's designed to feed multiple headsets.
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Old 26th Aug 2018, 12:31 pm   #3
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Default Re: WS19 set audio pick up...

I agree with M0sOe Bruce, pin 4 is shown on the circuit diagram connected to a tap on T2A secondary.

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Old 26th Aug 2018, 3:35 pm   #4
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Default Re: WS19 set audio pick up...

For maximum output, you need to match the output impedance to that of the speaker. The required voltage ratio is SQRT 100/8 which is approx. 3.5. I have successfully used a small mains transformer for this connecting the speaker to the 6.3V winding and the output of the set between the 250V and 230V terminals.
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Old 26th Aug 2018, 9:30 pm   #5
G4YVM David
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Default Re: WS19 set audio pick up...

Thanks guys

D
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Old 27th Aug 2018, 1:35 pm   #6
G6Tanuki
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Default Re: WS19 set audio pick up...

If you're looking at doing this, you could do a lot worse than get hold of a "100V line" audio transformer: these have a range of tappings on both the primary and the secondary so can be frobbed to provide a whole range of impedance-matches.

Whatever, don't expect the result to be very loud!
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Old 7th Dec 2018, 9:22 am   #7
G4XWDJim
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Default Re: WS19 set audio pick up...

Quote:
Originally Posted by G4YVM David View Post
Jim I can't make it but I need a transformer, something like a heater transformer, to use as an audio transformer in my 19 set. I want to drop the 100ohm to speaker values 4-8 I guess.

I could pay postage
David,

I probably have what you need but most of my transformers are in several large wooden boxes which I can't get into just yet but is a heater transformer really what you need.

A 240/6.3 heater transformer has a 40:1 ratio which is much the same as the average valve radio audio output transformer and would probably replace the 19 set transformer without the need for an additional one.

If you want to tack an extra transformer to the headphone output it needs to be a much lower ratio, about 2 or 3:1. A little transformer which I think would get near this and is readily available and cheap is the Eagle LT700. It's a small transformer intended as the push pull output transformer for little transistor receivers and is less than an inch cube in size. The primary which you'd connect to the 19 set headphone output is centre tapped and would give you a couple of ratios to choose from by using half or all of it.

The other thing you could do is use a redundant computer speaker with internal amplifier.

Best of luck.

Jim
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Old 7th Dec 2018, 9:58 am   #8
G4YVM David
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Default Re: WS19 set audio pick up...

Jim

Two good ideas. I have an amp here in fact, but we were trying to make it self contained...

Thanks again

D
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