10-02-2019, 11:11 AM
(This post was last modified: 10-02-2019, 11:17 AM by Old Sparky.)
As it's not my record player, but one I'm repairing for someone else, provided the BSR Cartridge(an SCR11 or 12) which is fitted to it, is in G.W.O., and gives reasonable output, I'll stick with the original circuit. Next job is to refit the amp. to the player, re-connect the motor & cartridge, fire it up and see, or rather hear, the result. By ensuring that all parts of the metalwork are at the same potential - the panel on/in which the controls are mounted was loose!) and fitting a 3-core mains lead, the hum level - at least with the amp. out of the cabinet - is very much reduced. Incidentally I note that there is an 1800pf cap. fitted between the anode & cathode in one version of the amplifier (not present in the one I'm repairing) What is the function of this cap. -I'd guess it provides some NFB, at higher frequencies, right?
