19-07-2020, 09:09 PM
(This post was last modified: 19-07-2020, 09:14 PM by Murphyv310.)
Thanks Rob.
OK so we know the output stage is working as it should. The things that can induce hum from V3 the phase splitter can be a leak on the valve base, an earth loop, leaky coupling capacitors C6 & C7. With V3 only in place what is the voltage on the EL84 control grids pins 3 with respect to ground -ve.
Oh and snip out that cap across the switch. Its not a snubber its for RF suppression which is irrelevant on a amp like this.
There is also the possibility that C2, 15uf is faulty a 16uf will do as a replacement.
Did you measure the resistance between pins 1 & 7 of the EZ?
OK so we know the output stage is working as it should. The things that can induce hum from V3 the phase splitter can be a leak on the valve base, an earth loop, leaky coupling capacitors C6 & C7. With V3 only in place what is the voltage on the EL84 control grids pins 3 with respect to ground -ve.
Oh and snip out that cap across the switch. Its not a snubber its for RF suppression which is irrelevant on a amp like this.
There is also the possibility that C2, 15uf is faulty a 16uf will do as a replacement.
Did you measure the resistance between pins 1 & 7 of the EZ?
Cheers.
Trevor
MM0KJJ. Member of, RSGB, GQRP, WACRAL, K&LARC.
Trevor
MM0KJJ. Member of, RSGB, GQRP, WACRAL, K&LARC.