SB 104A PROBLEMS

[John Farrington]

At 05:43 PM 01/03/2000 -0500, you wrote:
>I have the SB104 that the ARRL put together back in the 70's for the QST
article.  It was upgraded to the 104A.
>
>Now I have two problems.
>
>1. first,  The mic/cw Pot seems to give me a jumpy result on the
>      s-meter (power meter).  It seems to want to go wide open....
>2. second: much the same thing with the receiver RF gain.  it seems
>      to be working wide open...But, I still can't attenuate any
>      signals by turning the RF gain down.  Any suggestions?

Bill:
Can't offer any specific advice without doing signal tracing, but
I have a 104 that I upgraded to a 104A and it didn't have any such
problems; therefore, the most likely things in your case are wiring
errors or bad connections, either in the upgrade or the original
assembly. That upgrade kit was very extensive and complicated, so
it would have been easy for the builder to have made make mistakes.
If the mistake was in the 1st build, and the upgrade was added on
top without correcting it, then it will be extra difficult to find.
I can only suggest that you put on your magnifying glasses, get out
your VOM, and start tracing. Even connections that look good might
be bad, like those board plugs and solder joints.

And remember, the whole front end board was replaced with the
upgrade, so, if someone stuck the old front end back in and kept
the new one, there's no telling what the effects would be.

73

John Farrington  KE5ZB

Sponsored by the City of Tempe 

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