SB-300 Receiver problem

[Bob]

Hi,

    Sounds like the finger stock that mates the rotor with the frame of the
tuning capacitor is corroded or the bearings are also full of crud.  Open up
the unit and clean the bearings and the mating rotating surfaces of the
capacitor.  Craig Deoxit will do the cleaning and then a tiny  bit of
mineral oil in the bearings after they are flushed out with Deoxit.  Don't
use any abrasives to clean contact surfaces (pencil erasers are the tools of
the Devil) and so on).

    good luck

    Bob, KE6F
----- Original Message -----
From: Mark V. Johnson VE3DJU <mjohnson at CA.IBM.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Sunday, February 13, 2000 7:43 AM
Subject: SB-300 Receiver problem


> Hello All...Once again I'm turning to the collective wisdom of the team to
> offer an ideas regarding a problem I'm having on my SB-300 receiver.
>
> The rig is in fairly good shape...well built...no mods of any consequence.
> The problem..when tuning on some CW, RTTY or even the odd SSB signal, the
> signal sounds distorted/unstable or jumpy, when tuning it in..Almost like
> an unstable BFO on a cheap receiver. When you stop tuning (turning the
tune
> knob) the instability settles immediately. When you turn the knob to get
> the right pitch on a CW signal, it gets jittery again.  It happens in the
> USB and LSB mode, it is not dependent on the AGC setting, cutting back on
> the RF gain does not effect it, and it only seems to happen on some
> signals. Not all!! Not a big problem, but something's not right and it s
> gonna drive me nuts until I find it. Unless someone can tell me its an
> inherent design issue, which I doubt.
>
> Someone has been into the LMO as it is a 6CB6 tube( I believe a 6AU6 was
> std) and the screws are no longer sealed. . I put my scope on the LMO
> output and it appears very clean and stable. As I tune it, it changes freq
> very nicely..no apparent distortion.
>
> The problem occurs with the receiver in standalone mode and when mated to
> my  SB-400.
>
> Any ideas are welcome and appreciated!! TNX
>
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