[ARC5] Weird BC-453-B issue

[J Mcvey]

Well beat me with the "stupid stick"!!!!!
More errors-operator error this time. 
I rarely go below 455 KHZ, so when I do, i use an old URM-25 military generator.. I have the raw RF output to a frequency counter. This output has a switch that must be thrown when using that output below 300 Khz. I didn't throw that switch and somehow caused the output to the freq counter to have distortion or harmonics or something that the freq counter can't deal with. Now it reads correctly and I get tone output at 85 KHZ. 

I find that the injection results are  best if the tube cap is removed and a multi-K ohm shunt resistor is connected between the grid and ground to maintain the bias. A 270 pt cap in series with the gen and grid worked well.

Stupid stuff!!! 


Now I am working on the ARC-5 version (r-25) which is pretty deaf at this time. gotta open this one up. it's junk pile fresh...
 

    On Tuesday, August 29, 2017 4:39 PM, AKLDGUY . <neilb0627 at gmail.com> wrote:
 

 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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