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 Post subject: Add S-meter to Hallicrafters S-40
PostPosted: Apr Mon 16, 2018 3:36 pm 
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Joined: Feb Fri 22, 2013 5:04 am
Posts: 180
Good morning,

I have assembled the parts necessary to add an S-meter to a Hallicrafters S-40 general coverage receiver in a manner similar to an add-on S-meter kit that Hallicrafters actually sold. I also have the literature Hallicrafters provided with the kit to show how to install it.

However, with my ignorance on display here, I am not sure exactly where to connect the kit to my S-40 receiver. In the second schematic photo attached below, I have shown where I think it should go. Would I splice the kit in SERIES with the wire coming from T8? It looks as though this connection ultimately gets back to the plate return of V1, the RF tube. Is this correct?

Thanks in advance for any help y’all can provide.

Jamie


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 Post subject: Re: Add S-meter to Hallicrafters S-40
PostPosted: Apr Mon 16, 2018 4:01 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 6529
The meter assembly (with its associated calibration/compensation resistors) does go in series with the B+ feed to the RF stage. The tube current will vary with the AGC bias applied to the control grid of this tube with current dropping as higher AGC voltage is developed with higher level input signals thus providing the "S" meter action.

Realize that the meter will read backwards with "full scale" occurring at minimal signal and zero occurring with maximum signal level with your meter. Make sure everything in the added meter is insulated for full B+ because the resistors and meter terminals are at B+ above ground.

Rodger WQ9E


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 Post subject: Re: Add S-meter to Hallicrafters S-40
PostPosted: Apr Mon 16, 2018 5:32 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 343
Location: Limington, Me
I believe that all the S-40 series have a socket on the rear for connecting an S meter. Download
the manual from Bama for details for your particular receiver.

73, Roger


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 Post subject: Re: Add S-meter to Hallicrafters S-40
PostPosted: Apr Mon 16, 2018 5:48 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 6529
And the other Roger is correct! :) I was looking at a different setup.

Thank you for adding the correction.

Rodger WQ9E


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 Post subject: Re: Add S-meter to Hallicrafters S-40
PostPosted: Apr Mon 16, 2018 5:59 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1187
You'll have to ignored or redo the scale, but mounting an ordinary meter upside down will get it to swing the other way. :)


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 Post subject: Re: Add S-meter to Hallicrafters S-40
PostPosted: Apr Mon 16, 2018 7:45 pm 
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Joined: Feb Fri 22, 2013 5:04 am
Posts: 180
Thank you all for the replies.

I just finished hooking up the meter by splicing the two meter leads in series with the wire lead coming off of T8. The meter worked perfectly and I was able to attain both a mechanical and electrical zero.

And as Roger WQ9E said, the meter reads backwards with “5” on the right side of the meter scale as the true zero. The stronger signals move the meter pointer to the left toward “0” on the meter scale. The meter is very responsive and the receiver can be fine tuned rather easily.

Also, I know about the meter accessory socket on the back of the radio. From what I have read, it was designed for the SM-40 accessory meter also made by Hallicrafters. (The SM-40 seems quite different electronically from the meter kit I have assembled.). The meter socket supplies B+ voltage (pin #2), filament voltage (pin #1) for a dial lamp in the SM-40, a screen connection (pin #4) and a B- ground connection (pin #5). Pin #3 on the meter socket is not used. I couldn’t see how it would work with the wiring diagram supplied with the meter kit referenced in my OP.

Again, I appreciate the help received.

Jamie


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