[Boatanchors] Regenerative IF

[Roger Ruszkowski]

Bill,
 
You are looking for a bleed resistor in the AGC feedback voltage loop that is open or has a cold solder joint.
The function of the resistor is to bleed the excess voltage off the AGC that is setting the regen level in the feed back loop.
 
As you change the gain and set the regen stages into their high gain mode some caps get charged up to hold the regen voltage levels. This part of the circuit works OK. As you back the gain down the control voltage should decay and  let the stages drop out of regen or high gain operation. We expect a bleeder resistor to be present and providing the discharge path. A resistor is not doing the job it should do. I will hold out for crud on a switch contact or tube pin socket then a cold solder joint, then a broken resistor and then a resistor way out of its original resistance range, (burnt). 

Good luck and happy troubleshooting.

Roger Ruszkowski AI4NI
 
 
-----Original Message-----
From: Bill and Liz <magoo at isp.ca>
To: boatanchors <boatanchors at mailman.qth.net>
Sent: Sat, Dec 27, 2014 4:58 pm
Subject: [Boatanchors] Regenerative IF


I have a homebrew receiver in the shop with a funny problem.  It has a 
regenerative IF stage and if you accidentally run up the regen control too far 
it breaks into oscillation and won’t come out for several minutes.  The whole 
receiver is “paralyzed”-there is no reception at all; very slowly it begins to 
recover, a process which takes another few minutes.

Anyone suggest what is happening and possibly how I can stop it from happening?  
I have no experience with regenerative receivers.  Other regen receivers I have 
played with will go into oscillation but will come out quickly as soon as you 
back off the control below oscillation point.  

Bill VE3NH
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