the standby switch opening the cathode path to ground makes me nervous.
Maybe the switch arcs when it opens.
I'd find a different way to put the amp in standby or at least put a snubber cap across the switch.
Maybe wire a switch in series with R74 and let the negative grid bias go way up to cut the tubes off.
mark
4.am4...
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hent.
ins
. sWhat I can't understand, from the schematic you linked, are the lack of fuses between the Xformer and the bridge rectifiers. Looks to me like a disaster waiting to happen. We add fuses in low voltage circuits like that to protect the transformer as the primary fuse rarely blows when a secondary bridge shorts out - at least the primary fuse doesn't typically fail until things have gone very wrong in the Xformer...
On our old tube amps, as used in jukeboxes, the practice was to turn off
the B+ for standby, this greatly reduced heat as well as wear & tear on components.
John :-#(#
** A switch in the supply to the output tube's screens works well - assuming beam tubes or power pentodes are in use.
Only a few mA need be switched at idle and no electros to discharge.
..... Phil
** A switch in the supply to the output tube's screens works well - assuming beam tubes or power pentodes are in use.
Only a few mA need be switched at idle and no electros to discharge.
..... Phil
************************************This seems to be a very simple and elegant solution, yet I have never seen it in use.
Is there a reason this has not been more widely used?
Gareth.
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