Re: Help - B3 Intermittent loss of highs and intermittent hum

[bobs@hopf.dnai.com (Bob Schleicher)]

>At 13:13 29/12/95 -0500, edpayne@infi.net wrote:
>
>>My B3 intermittently cuts out, best described as a loss of highs, diminished
>>volume, and sometimes accomp'd by 60Hz hum "
>
>
>  _____________________________________________________________
>  Marco Montaruli, General Plastics - Rome <genpla@flashnet.it>
>
>
>Check the tone control.  Sometimes spraying cleaner into it and rotating to
the limits several times will cure, or just replace it (300K linear).

You might want to replace the cathode bypass caps on the 12BH7 and the
12AX7, which is common to the 6AU6's too.  They may be part of a 4 section
electrolytic, or tubulars.

Make sure there is no "growth" around the swell cap., and check the shielded
wire from the swell cap (green in a spring type gizmo) has about 1/8"
clearance at the end that goes to pin 7 of the 12AX7. I've seen the spring
move forward and try to ground the grid of the tube.  You might also want to
check the volume solt switch for "growth".  If all that fails, try C16, .033
from 12AX7 to the swell comp. network and C23 same value from pin 6 12AX7 to
the volume soft switch.

Hope thats of some help and good luck.

Bob S.