[ARC5] OT? bc-348 bfo question

[Fernando - LU2DFM]

On Sat, Sep 14, 2013 at 06:18:13AM -0500, John Hutchins wrote:
> Fernando
> If you have a previously hacked set go for all kinds of
> modifications, in fact I would encourage it.  Otherwise I suggest
> only making modifications that are easily reversible.

This receiver was salvaged from scrap, it was previously beaten and
modified to sick, I taked it apart _completelly_ to revert back
modifications and correct wiring.

I'm taking flak here for hacking, even when I said nothing of
modifications of any kind, reversibles or not. I'm trying to get
knowledge about the circuit of the receiver.

> 
> I have listened to SSB for years on MVC using the R series of the
> BC-348 no problem.

I'm also. That's pretty much what I expect from this kind of receiver.

 
> Suggestion if your set does not have an Antenna trim control suggest
> mounting a variable capacitor 75 ~150 pf with an isolated shaft/ or
> using an  isolator coupler in a box and connect your receiver
> through this to your antenna.  Trimming helps a lot to get the
> signal up.

The receiver has it's original antenna trimmer. In fact, I managed to
get it close to original look and circuit. Missing: output
xformer-choke, back connector, dial light rehostat, couple of knobs
(AVC-OFF-MVC lever notably), original antenna post, one of the long
screws that set the cabinet.

> Next the next check the AGC/AVC timing capacitor (123-C on HKLR
> series, 64 JNQ series, 101 EMOPS series) .05 uF  I see ~100 V PP
> some times on real strong signals.  The cap typically is 400V paper.
> So draw your conclusions there.  In the HKLR series it is mounted in
> the transformer CAN!
Done. 

> 
> Also check the existing cathode bypass capacitor of the 2nd
> IF/Detector circuit (9-16 EMOPS series, 70-B JNQ series, 11-16 HKLR
> series) .  This also is a paper cap, same conclusions here.
> Next I suggest a mod that is easily reversible: add  5uF ~200V
> capacitor across the cathode bypass capacitor of the 2nd IF/Detector
> circuit this may help.

Cathode of 2nd IF/DET or 3rd IF/DET? I think you mean the later.

Thank for your input.

-- 
73 de Fer, LU2DFM