[ARC5] Weird BC-453-B issue

[AKLDGUY .]

As I have pointed out before, if a decoupling cap at the bottom of an IF
transformer winding is faulty, missing, or internally destroyed, the tuning
of the IFT will be badly affected. In the worst case where a cap is
actually missing, there is only wiring capacitance to perform the necessary
decoupling.

Always check the likely suspects first.

73 de Neil ZL1ANM


On Wed, Aug 30, 2017 at 7:47 AM, J Mcvey via ARC5 <arc5 at mailman.qth.net>
wrote:

> Some of the mystery has been solved.
> 1) equipment failure. I was using an  adapter from the signal generator (
> N to BNC and BNC to binding post ) . Did have the N tight enough , so there
> was massive attenuation.
> 2) stray RF in the shop  causing false results.
>
> I still can't inject the 85 Khz IF with any success, but the radio does
> work!  I resorted to plan B and decided to just peak the IF's on a known
> signal.
> The dial is almost spot on. I peaked the IF's , then zero beat the BFO .
> The sensitivty on AM is about 3 microvolts and about 1 microvolt in CW.
>
> What am doing wrong with the IF injection?
>
> I think I'll replace the remaining caps as well.
>
>
> On Tuesday, August 29, 2017 2:23 PM, "arc5 at ix.netcom.com" <
> arc5 at ix.netcom.com> wrote:
>
>
>
> First- check your BFO operating freq.  If it is not 85KC, determine why.
> 2nd- put 85 KC at Mixer output.  Scope output of the 1st IF transformer.
> If it does not peak at 85 KC, find out why not.  If you can't peak the
> output at 85 KC, sub the transformer (write it you need subs). Repeat with
> next stage.
>
> Sent from my Ain't Smart Phone.
>
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