GB Battery +/- polarity confusion

[AlanBeckett]

Ah, but ...
The Red Wire should go to the End of the Battery which is labelled +
The Black - Negative - Wire should go to one of the Taps which are Labelled progressively from the +.

When Transistors were staring to become available at a sensible Price I used to use them for 'Projects' aka 'Messing about' as my Mum put it

Alan

[Crackle]

Yes David, your sketch made sense to me.

Mike

[Terry]

That wasn't me, it was David. I've only just caught up.

Sorry, Alan!

I'm reading (and writing ) this on a very small screen and must have picked your name by accident!

[Terry]

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 ...

[Terry]

OK, I've been lugging - well, the car has! -  this laptop around the Wet Midlands and Central wales for a week so I suppose it's time I booted it up and anyway, the phone needs charging ...

Here's a typical grid bias battery - note the markings:



Translating this into David's drawing gives us this:

   

See the difference?

Considering Nick's confusion in the original post, it is important to get something like this right to avoid spreading further confusion.

At least, that's my attitude - your's might differ ...

[Mark Hennessy]

At least, that's my attitude - your's might differ ...

Please, let's keep this civil

[Old Sparky]

Hopefully my post earlier helped to clarify things, rather than 'stir it up'. Admittedly I hadn't thought that the way grid bias batteries are (were) marked might be a bit ambiguous, but then, I remember my father talking about them (He had at least one radio which used 120v. HT & 9v GB Batteries, plus a 2v Accumulator, but I've never worked such a radio, or even seen one for many years.

[Yorkie]

Thanks for your input and the pic Terry.

For the avoidance of doubt, I've amended the sketch to correctly depict the actual voltage readings as shown on GB batteries, which is attached below.

(Nick's first homebrew Grid Bias Battery was a stunner - not doubt this one will be too).

It really dates me to recall that GB Batteries were still being sold by the likes of Woolworths into my early adulthood!

[SurreyNick]

I'm glad you showed that picture Terry. If I put the positive probe of my DMM in the +0 tap and the negative probe in the 1.5 tap should I get a positive or negative reading on my DMM?
Nick

[pwdrive]

Negative.

Lawrence