[Heath] SB-101...more problems....

[James Owen]

Hi Gary,   A few thoughts here as I just completed rebuilding an SB-101 and have a HW-100 on the bench as the present time.   How do you determine that the CW position doesn't work? If it didn't then you would have no output when in the tune position as the CW  crystal is switched in only in the tune position and CW position on transmit. It's not used when in receive.    If the carrier won't balance completely several things to check. One be sure the balance pot is good as I found one end in mine was broken. Check for resistance across the pot (one end disconnected) and look as how smooth the resistance is from the center to either end.  If still not balanced you may have a bad diode in the balanced modulator or even a defective T1 though it's unlikely it's T1.  This is a pretty simple circuit and not many things to go bad.    As far as the wires disconnected it sounds like someone modified the audio output to drive something other than the speaker. The green wire from the transformer goes to the speaker through the phone jack and you would have no output if that disconnected.The cable on "B" goes to one end of the VOX anti-trip pot and circuit would work with this disconnected. I would put the circuit back to the original design.
73 Jim
 James C. Owen, III K4CGY

      From: Guy Giacopuzzi <gggdds at js-net.com>
 To: heathkit listserve <Heath at puck.nether.net> 
 Sent: Sunday, March 27, 2016 8:07 PM
 Subject: [Heath] SB-101...more problems....
   
  Well, I got the LMO working right, and tuning in the correct direction, but I've got other problems...CW position just plain doesn't work, and I've got carrier--what I feel is too much--when using both the LSB and USB modes...tuning the carrier null cap and pot lower it, but not enough...I think the problem's in the carrier oscillator or balance modulator, but I haven't had to time to check the voltages...(I have had time to do the resistance checks per the manual, and they all seem ok)
 
 One other odd thing...I found the green lead from the output transformer cut, and three of the shielded cables in the same area disconnected...the blue one going to "B" on the audio circuit board, and two white ones...one going to the speaker rca plug, and one going to from the green lead of the output transformer back to the phone jack on the front....wonder why?
 
 Guy -- 
  
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