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 Post subject: DFD1 digital readout
PostPosted: Nov Thu 16, 2017 7:24 pm 
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Joined: Aug Wed 25, 2010 3:23 pm
Posts: 1129
Location: WA 98407
Anyone remember these now obsolete units? I bought one 10 or 12 yrs ago to use with my SX-28. Despite my lack of training and expertise I managed to complete the assembly and adjust it for use with the intended receiver. It worked very nicely. Then one day, never having acquired a frequency counter, I "undid" the LO offset to use it as a frequency counter :oops:

Now I would like to return the DFD1 to its intended use. But I can't remember how it's coupled to the receiver (I can find only a few pages of the original documentation, and not the one for those instructions). Through a small cap to the grid or cathode pin of the mixer tube? Or the oscillator tube? Both are 6SA7s. I tried that and the display is not reacting to whatever signal is present on either pin 5 or pin 6 of either tube.

To test that it actually works, I coupled it to the oscillator of another radio. It worked, although the display showed twice the nominal frequency of the oscillator. So, any suggestions for the SX-28? Thanks!

Tom


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 Post subject: Re: DFD1 digital readout
PostPosted: Nov Thu 16, 2017 9:39 pm 
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Joined: Nov Sat 07, 2009 11:37 pm
Posts: 1775
Location: Sayreville, NJ 08872
Might find some info here:
https://web.archive.org/web/20040210140 ... 0/dfd1.htm
The DFD1 manual:
https://web.archive.org/web/20040210214 ... 1inst.html

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Pete, WA2CWA - "A cluttered desk is a sign of genius"
http://www.classicradiomanuals.com


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 Post subject: Re: DFD1 digital readout
PostPosted: Nov Fri 17, 2017 1:06 am 
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Joined: Aug Wed 25, 2010 3:23 pm
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Location: WA 98407
Thanks Pete. Buried in there was an indication that tying it to the cathode of the LO was correct. Thanks for finding those links.

Tom


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 Post subject: Re: DFD1 digital readout
PostPosted: Dec Fri 01, 2017 1:39 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Warner Robins, GA
I have one of those and in order to get mine to work with my SP-600 without pulling the oscillator frequency while getting a reliable display I had to use the preamp board (mounted it inside the case) and mount a jack on the radio chassis near where a wire carrying the LO signal runs.


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