28-10-2015, 05:21 PM
David,
The markings on your battery are the problem.
Yours are:
-0V 1.5. 3.0. 4.5 6.0 7.5. 9.0
But they should be:
-9.0 -7.5 -6.0 -4.5 -3.0 -1.5 +0
You show the -9.0V connected to the grid and the -3.0V connected to the chassis. There is indeed 6V negative on the grid wrt ground but that is not the right way to do it!
Anyone wanting a -3V supply for an earlier stage is going to be particularly confused because the terminal on the battery MARKED -3.0 is already in use!
I don't seem to be able to add pictures on this phone but if you Google 'grid bias battery' and select images you will see pictures of several batteries with the outputs clearly marked on them. None that I can find match David's drawing ...
The markings on your battery are the problem.
Yours are:
-0V 1.5. 3.0. 4.5 6.0 7.5. 9.0
But they should be:
-9.0 -7.5 -6.0 -4.5 -3.0 -1.5 +0
You show the -9.0V connected to the grid and the -3.0V connected to the chassis. There is indeed 6V negative on the grid wrt ground but that is not the right way to do it!
Anyone wanting a -3V supply for an earlier stage is going to be particularly confused because the terminal on the battery MARKED -3.0 is already in use!
I don't seem to be able to add pictures on this phone but if you Google 'grid bias battery' and select images you will see pictures of several batteries with the outputs clearly marked on them. None that I can find match David's drawing ...
