[Heath] Dead SB-101 IF?

[Kenneth G. Gordon]

On 21 Nov 2015 at 12:12, Alexander N. Gerli wrote:

 
> I have a working LMO, rx audio stages and the LSB and USB 
> oscillators are working (LSB and USB settings sound correct), SSB 
> and CW Filters seem correct, RF and AF Gain controls work and the 
> S-Meter Zero control zeroes correctly.

Hmm...if the S-meter zeros correctly, then the IF stages are working.
 
> Now...the Preselector doesn't work. no change in tuning sensitivity 
> regardless of band. I CAN hear a signal. At the top of the LMO, like 
> 490 out of 500, I hear a type of beacon signal fairly weak from WLO, 
> a commercial mobile Marine Radio voice/data station located in 
> Mobile AL. AND, the signal is there regardless of the chosen band 
> (so just the LMO is being amplified, right?). The frequencies they 
> operate on are not anywhere near the LMO range of 5-5.5MHz.
> 
> Somehow the IF and mixers are not working.

No. I think the IF is working: the mixers may not be working, but that is 
probably because one of their input signals is not there.

It sounds to me as though your heterodyne oscillator is not connected or not 
working. I would start there.

I assume you have a 'scope? Do you have a manual or a PDF copy of it?

There is a heterodyne oscillator test point near V-19, a 12AT7. There should 
be at least 2 VDC on that point on each band.

If there is 2 VDC or so there, then the output from the heterodyne oscillator 
cathode follower may be shorted or open. You can also connect a scope 
there and take a look at the heterodyne oscillator signals. They should 
change frequency for each band switch position.

Please check your heterodyne oscillator out thoroughly then report back.

vy 73,

Ken W7EKB