(20-04-2013, 01:51 PM)pwdrive Wrote: The LH triode must be hard off with - 140v on the grid?
Lawrence.
Yes: it must be. The cathode is at 0 v., so with -140 v. on the grid, the valve cannot be conducting.
But can anyone tell me why C518, 1 nF, is there? What's it supposed to do? At first, I though that is passed a -ve going spike from the half-wave rect., until I saw that C508, 0.01 uF, is connected to 0 v. Hence, C518 is effectively short-circuited to 0v. by C508.
And, perhaps more to the point, where is the -150 v. at the grid of the RH 12AU7 coming from?Al.
