On Fri, Jan 10, 2025 at 10:21 PM, Roger KW4EMF wrote:
<I've looked at several internet posts about checking the 500z's with a multimeter. If I understand this correctly. Two of the pins are the filament and three of them are grids. What should the readings look like when <checking them with the ohm meter? The tubes are out of course.?
<Thanks
?
Pins? 1+5 are the cathode...and will read zero ohms, or close to it.??
Pins 2+3+4? ?are all tied internally to the grid.? You will see zero ohms between any of the grid pins.?
And u will read a wide open? between cathode and grid.
Grid to cathode shorts are not uncommon, but that never happens till the fil is lit.? A good eimac 3-500Z will hi-pot test 5 kv between grid and cathode/fil .? ?A chinese? 3-500Z will hi-pot test 1 kv? between? grid and cathode.?
U need to go through every inch of that amp.? 1400 watts on 20m..and only 400 watts on? 40+80m is indicative? of either a bandswitch problem / coil tapping issue, on the kw output side, or a tuned unput bandswitch problem, or tuned inputs.? ?and now u are down to 400 watts on 20m.?
You can also pull one tube out...and test with remaining tube, and vice versa.? ?It could also be an issue with one or both sockets.? ? It's a simple amp, in its basic form it's a pi tuned input and pi tuned output.? Metering,? B+, fil V, and a tr relay.?
