30-11-2016, 11:43 AM
(30-11-2016, 10:29 AM)Sparks Wrote: Well it isn't!The readings are only correct with G3 left disconnected!
This doesn't give me any cause for concern, I long ago discovered that theory does not always match up with fact when it comes to radio,
There is always an explanation for something so well understood as radio.
Real radio theory always matches reality when the measurements are done properly and the correct theory properly applied.
It gives me great concern as is means something is wrong. An electrode should always be connected to somewhere, never floating. I'd not want visitors to the site to get the idea that valve testing can be done with unconnected electrodes.
It absolutely connects to cathode in Pentode mode (g2 and anode are isolated supplies) and on an EF39 it *might* connect to anode if g2 and anode are using the same supply (triode mode testing). I'd have to check what the Philips data or construction says.
If there is no separate g2 HT, then it's only testing pentodes as triodes (g2 connected to anode).
