[Vintage-Radio] s-77 strange hum

[Anthony W. DePrato]

Well i pulled the old S-77 Hallicrafters out of the pile it was time to 
start the restoring. replaced the cracked ac wire. checked for any signs of 
burnt resistors . put it on the variac and brought it up. loud hum in 
speaker vol control had not effect on hum . ok lets check the filters. dig 
in my boxes of NOS muilty CDE caps. found a match. hooked it in line . 
powered back up. hum still there . ok  by passed most of the caps with a 
new one just to check . hum still there. well. ok lets check the tubes. 10 
mins later all tubes checked good. ok reverse the ac plug still there. 
tuned around on 10 MHz shortwave head a station under the hum. now this is 
strange. wonder if the ballast tube could be causing it. started to 
disconnect the antenna wire that was hanging from A1 when i got it. well A2 
and G are strapped together. remove strap hum goes AWAY.  receiver works 
great. strange what you run into at times. now to recap it and have fun
73 Tony WA4JQS