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

[Guy Giacopuzzi]

Jim,
I've got something intermittent....just got the carrier balance to 
work.  "Tune" works but CW doesn't, though last night, it worked for a 
while...the key keys the tone oscillator, and the tone oscillator puts a 
signal into the vox amp and activates the relays; when I checked the 
tone oscillator, there was zero output when keyed...
I did rewire the  audio to original design, and now it appears the avc 
isn't working; I have to back off the rf gain for every different 
signal, or it distorts...

Guy

On 3/28/2016 11:45 AM, James Owen wrote:
> 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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