[ARC5] Weird BC-453-B issue

[Bruce Long]

Did you use a dc blocking capacitor or the equivalent when applying the 80 kHz test signal.  If not your test lead connection could have easily badly upset the bias required for the tube to work.


      From: AKLDGUY . <neilb0627 at gmail.com>
 To: J Mcvey <ac2eu at yahoo.com>; ARC-5 List <arc5 at mailman.qth.net> 
 Sent: Tuesday, August 29, 2017 4:42 PM
 Subject: Re: [ARC5] Weird BC-453-B issue
   
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.
______________________________ ______________________________ __
ARC5 mailing list
Home: http://mailman.qth.net/ mailman/listinfo/arc5
Help: http://mailman.qth.net/mmfaq. htm
Post: mailto:ARC5 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

   
______________________________ ______________________________ __
ARC5 mailing list
Home: http://mailman.qth.net/ mailman/listinfo/arc5
Help: http://mailman.qth.net/mmfaq. htm
Post: mailto:ARC5 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html


______________________________________________________________
ARC5 mailing list
Home: http://mailman.qth.net/mailman/listinfo/arc5
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:ARC5 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

   
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20170829/216c36dc/attachment-0001.html>