SB-313 Receiver Problems

[Jim Bo]

Joe,

Ok, got the LMO out and took off the bottom cover.  The tuning cap is covered
with a piece of metal that is solder to the housing that holds the cap.
Can't see any plates or piston of the cap due to the cover.  The metal side
of the LMO housing does not allow me to get at the plates of the cap.  There
is a copper ground strap that connects the top of the metal plate (the metal
plate is soldered to the metal housing that surrounds the cap) to the LMO
housing, and the solder "fillet" looks good.  The metal mechanical "stops"
(the ones that turn when you turn the shaft) on the shaft are easily seen,
and I have cleaned that mechanical interface with some "Tuner Control Cleaner
and Lubricant".

I don't see the end stops that you refer to, they appear to be buried below
the tuning shaft, so I can't get at them to solder.

Any ideas or comments from all in the group?

Thanks in advance.

Jim
***

Joe wrote:

> Common problem, you have a poor ground path (oxidation) on the tuning cap
> shaft contacts.
> Clean up the 2 rotor shaft contacts.
> You can also improve the path by adding some braid from the shaft stop
> points to gnd.
> -----Original Message-----
> From: Jim Bo <jbollit at IX.NETCOM.COM>
> To: HEATH at LISTSERV.TEMPE.GOV <HEATH at LISTSERV.TEMPE.GOV>
> Date: Monday, September 06, 1999 8:13 PM
> Subject: SB-313 Receiver Problems
>
> >I have an SB-313 with a problem and I am hoping someone here can
> >help me.
> >
> >The radio receives short-wave stations, but the tuning seems
> >"noisy" and you will get heterodynes when tuning.
> >
> >If I have a station tuned in, just moving the tuning dial 0.5 Khz
> >will result in noise or static in the speaker, sounding like a
> >dirty pot.  Additionally, the station may jump in frequency or
> >all together not be heard.  Rocking the VFO back and forth with
> >produce the scratchy noise and cause loss of the station at
> >times.  If I tune a station and just leave the radio alone, it
> >receives fine, with good audio and signal strength.  But if I
> >touch the VFO knob, I get the noise and loss of station and
> >sometimes heterodynes.
> >
> >I have removed all the pcb's and "retinned" the copper tracks so
> >they make good ground contact, and I have tried terminating the
> >output of the LMO with 47 ohms with no luck.
> >
> >Any ideas out there?  Sure would like to get this radio working.
> >
> >Thanks
> >
> >Jim
> >
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> >
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