[sdiy] Tubin'

[René Schmitz]

Hi Pat,

> I've been attempting to do some experimentation, and of course have come up
> with a couple of questions.
> 
> I'm working with a 6Y6G Pentode, and have found a datasheet here;
> http://hereford.ampr.org/cgi-bin/tube?tube=6Y6G
> I have very little experience with tubes, and I don't quite understand the
> base diagram.  I know which is which as for grids, plates, and heaters, but
> what I don't understand is the pinout.  There is no pin at the sixth
> position, which I would expect, but there is one at the first position.  Can
> anyone tell me if there are any special considerations for pin 1? (I'm
> assume it's "Not Connected", but what does the S mean in S/NC?)

In this datasheet, its a bit clearer. There is no "S". :-)
http://frank.pocnet.net/sheets/127/6/6Y6G.pdf
Pin 1 is not connected, and pin 6 could be missing.

> Also, have any of you used a full wave voltage quadrupler to get a descent
> plate voltage?  I've tried and tried tonight with no luck.  The two books
> that I found schems in were both slightly different, but neither on gives me
> an output.  Any other recommendations for a simple way to get approximately
> 100 to 135 VDC from a 28V transformer?

I've used doublers, and they worked fine. A little easier is to use two 
transformers back to back.

> What will the consequences be of running the heater on about 4.7 VAC instead
> of 6.3?  I'd be finding out for myself right now, if I could have gotten
> that quadrupler to work before getting to tired.  Oh well.

If you underheat the cathode over a long period, it could ruin the 
emission capability of the cathode. Also on a shorter time scale, it 
would mean that the transconductance of the tube is degraded, and that 
you can't get the full cathode current and power output. I would try to 
rectify the 4.7V with some schottky diodes, and add a filtering cap.

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159