Nah. If it were a piece of wire, it should be about .01 Ohms. 1/2 Ohm would be a really lousy piece of wire (maybe #30 AWG?). Directly grounding the grids saves a lot of problems.
Thanks again everyone will definitely look at measuring resistance I think its a newer amp tho but will check later.... Thanks Christoper
Maybe .01 with a milli ohm meter and carefully prepared surfaces... A regular man's DVM will see ~.2 ohms with the leads shorted... But that's beside my point. I want to know what version of this amp M0TRJ has and if there is something wrong at the sockets without taking the tube mounting plate out of there (a mini PITA). ... we're looking for a few good clues in the game of, "Repair by Remote."
Yes, I forgot they have those Grid resistors . . . Definitely worth measuring, as if they have gone high (due to flashovers inside the Valves in the past) this might cause the problems you are seeing. Best measuring from the top of the valve base (as suggested) on each one . . . as like most repairs or even tests on these Linears, you can't easily get to anything! (one of the reasons I hate them!) Roger G3YRO
Ok Christopher i have mailed you some pics of grid and believe that the amp was built july 2012. I get no reading between pin 2 and ground but do from pin 3
I believe the ones made after 2010 went to directly grounded grids. That's why I figured a simple test would help us figure out which amp Simon has... I really hope it is an older one. Bad grid resistors would make sense here. Of course, then you have to take the mounting plate off anyway.
Well, I must have drawn the diagram backwards... the grid is one of the little pins. The other little pin is open. The two big-uns are the filament lines. If the reading from what I marked as pin3 to ground is < 1/2 an ohm on all three of them, it's a newer style amp with the grids directly grounded and we can forget about bad grid resistors there. Maybe it will just work with the new valves!
