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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 10th May 2018, 4:39 pm   #1
G4YVM David
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Default WS19. No audio.

I've got my friend's 19 set going to the point that the heaters glow etc. I'm sure it does work fine, but I can't get audio from it. I am connecting a speaker to the pin 4 and chassis but get nothing. Now, is this because the modern low impedance speaker won't do the job or because I might have an issue? Pin 4 on plug 2A is the right pin, the intercom relay works which makes me think the set is fundamentally fine, so what am I missing?

David
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Old 10th May 2018, 5:32 pm   #2
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Default Re: WS19. No audio.

Make sure the receiver is receiving and look at the attached schematic and description.

I would go to the cap of the 6B8 G.

What you would be missing is a cup of tea instead of digging into 60+ years of crystalized crud on the wiring under the chassis.
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Last edited by radiotechnician; 10th May 2018 at 5:33 pm. Reason: word missing
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Old 10th May 2018, 5:33 pm   #3
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Default Re: WS19. No audio.

I thought the 19 set only drove headphones unless someone added an audio power amp stage.

How original is it?

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Old 10th May 2018, 7:09 pm   #4
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Default Re: WS19. No audio.

I think mine is headphones only.
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Old 10th May 2018, 10:51 pm   #5
mike g3zii
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Default Re: WS19. No audio.

Hello, You should hear something on the headphone output with a speaker.
On mine unmodified, it's there but not super loud. I matched mine to a 3 ohm speaker by using the rx output transformer of a Pye vanguard . the winding driven by the transistor output steps down the impedance and ups the power output.
but you probably have not got one of those handy.
I would do some fault finding around the 6B8 stage as already suggested.
The output transformer could be suspect. best of luck with it.
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Old 10th May 2018, 11:19 pm   #6
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Default Re: WS19. No audio.

Quote:
Originally Posted by G4YVM David View Post
Now, is this because the modern low impedance speaker won't do the job or because I might have an issue? Pin 4 on plug 2A is the right pin, the intercom relay works which makes me think the set is fundamentally fine, so what am I missing?
David, if the speaker is not matched you should still hear the audio, it will just be quiet.

Actually, I'm pretty sure that this set would have had similar audio power output power and headphone impedance to the ZC1 receiver. If you scroll to page 77 of this article, there is a method to make a small extension speaker box and impedance match it. Even though the ZC1 had only an RF pentode as the audio output valve and was made to drive headphones, a correctly matched speaker gave more than enough volume in a standard room. So I think this method would work for your 19 set too, after you have fixed the current fault.

http://worldphaco.com/uploads/ZC1_MK...R_SUPPLIES.pdf

Hugo
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Old 11th May 2018, 1:27 am   #7
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Default Re: WS19. No audio.

Here is a picture of the earphone cone for WS19 headgear
that was used in the tanks. The DC resistance is about 64 ohms.

I believe the output impedances for the B , A , and intercom
sets was 500 ohms. The level would have sufficient to travel
through field wiring to reach a remote operating R/T post.

Both the microphone and earphone used the same cone type
speaker assembly (as far as Canadian apparatus that I had
worked with). The remote station microphones and earphones
were carbon, and non-cone telephone type.

There were groups of WS19 aficionados who owned the sets
and held ham radio events with them.
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Old 11th May 2018, 2:15 am   #8
Argus25
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Default Re: WS19. No audio.

Quote:
Originally Posted by radiotechnician View Post
Here is a picture of the earphone cone for WS19 headgear
that was used in the tanks. The DC resistance is about 64 ohms.

I believe the output impedances for the B , A , and intercom
sets was 500 ohms.
That is close to the ZC1 earphones that I think were 100 Ohms DC resistance and the impedance not a lot different.

With a pair of small 32 ohm speakers in series then, the 19 set would probably have plenty of audio output and not require a matching transformer.
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Old 11th May 2018, 6:18 am   #9
G4YVM David
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Default Re: WS19. No audio.

Thanks all. I tried adding a simple resistor to the speaker line then I removed it and usd an audio amp I built instead. Now I get audio but it's just noise and hash. No signal gets through it all, even when 'injected'from a nearby transmitter.

Methinks she is dead somewhere. The audio valve is heating ok.

D
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Old 11th May 2018, 7:23 am   #10
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Default Re: WS19. No audio.

As mentioned the ws19 will drive a 3 Ohm speaker but it will be low volume and will dampen the mod on transmit. I use a 600 Ohm speaker as used on some communications receivers and it works fine. Do you have any indication on the AVC position on the meter switch with a strong signal?
I have had problems with the toggle switches failing or sometimes just not switching on if not used for some time.
Don, m5aky
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Old 11th May 2018, 8:15 am   #11
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Default Re: WS19. No audio.

The output transformers (T2A) have a tendency to go o/c primary (probably due to the dreaded "green spot" corrosion). As Don has said, with an input signal, you should see a (downward) deflection on the meter in the AVC position if the RF side is working. Another source of possible problems is dirty relay contacts. All the circuit information, etc, is available for download on the VMARS manuals page.
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Old 11th May 2018, 9:06 am   #12
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Default Re: WS19. No audio.

If it turns out to be the output transformer, Sowter were making replacements. Last time I checked the price worked out at about £60.00 including VAT and carriage.
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Old 11th May 2018, 6:43 pm   #13
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Default Re: WS19. No audio.

Hi David

As already suggested T2 has a tendency to fail, also, a good dose of switch cleaner can work wonders round the relays and wafer switches. [don't forget the meter switch it can produce false readings].

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Old 14th May 2018, 10:14 pm   #14
G4YVM David
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Default Re: WS19. No audio.

Thanks all, I'll either work on this or not...trouble is, the owner has now bought aT1154/R1155 so this 19 set is effectively surplus. We shall see.

Thanks though...I'd like to fix the audio.
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