The AM Forum

Hello!

I am seekign input on a planned circuit.

I want to put a couple of 4D32's in parallel, with about 800 to 900 volts on the plates, and 400 on the screens.  AB1 grid bias should be around -37.5 VDC, but someone please check.

I want to drive the pair with a 6AG7.

What would the plate resistance be for such a pair, approximately?  What sort of bias supply would be required?

Thanks!

Matt

push pull or single ended .... audio or rf ?

RF. Single ended.  It will amplify the AM from an HP-606A.  The 606A will go into a 6AG7.

The 4D32 will be single ended, parallel.

Thanks!

For AB2:
600 volts on the plates, 250 screen volts (well regulated), -25 volts bias well regulated, 100 to 365 ma plate current, 26 ma screen current, 3k ohms, 125 watts out.
Takes half a watt drive to get there.
30 watts carrier output in AM.

AB1 power out would be about 15 watts?

I would like to push the plate voltage.  About 800 to 900 VDC.

Ideas?

Would a Heath IP-17 handle the grid bias, or something heavier?

With AB1, no grid current..........attractive.


This thing is going to have a plasma tube as a load.

Plasma tube load?? Wazzat? Pic?

Grid bias is nil current. Anything will do that.
AB2 is mo' bettah.
I think you'd do bettah with PP over SE parallel, unless your goal is a lower output Z from
the tubes.

AB2 requires DC coupling (xfmr is one way) to the grids. Easy enough if ur not needing to
be extremely frequency agile.

sounds like a fun project.

                        _-_-

Just up the bias and screen volts to get 900 volts on the plates to run.
Only testing will tell how much power you get out in AB1.
Its likely to be quite low.

I thought of push-pull, but want to run the plasma tube single ended, with one end going to a decent ground.....maybe some radials in the soil.

Must be agile.........200 to 300 Khz, up to 1600 to 1800 KHz.  No better VFO here than a 606A!

I am OK with AB2, but need a way to bias the grid without trouble.  I am going to make a set of coils for the input LC circuit............Pi coil big, with many taps.

Pi tank out, but then a link coupling to a secondary parallel LC tank.  One end of the plasma tube taps this tank coil.  The other end to ground.

Plasma tube is two electrodes spaced about 10 cm in a large pyrex tube.  Tube charged with about 20 mm Hg of helium gas.

See rifevideos.com

Fasten your seatbelt.  Sensory overload ahead!


Matt :-)

I guess they could be run push-pull.  Link couple to the single ended secondary tank.

Grid bias is my concern.  How about a resistor in series with the parallel LC grid input circuit?  Or a decent sized choke?

How about zener cathode bias? Its simple. Other methods will work. This can't be an amateur radio device.

Must be medical quackery if its this rife device from the 1920s. Maybe you have something there ;D

Its a project.

Al VE3AJM

watch out for generating X-rays. Not saying it does or will, just saying be careful and actually measure/test.

grid bias can be via a CT secondary - the turns that drive the grid. Air core, it cares not about DC.

                    _-_-

How would any significant (maybe any) x-rays be generated with a plate voltage of 900?

don't believe you will .... went thru a calculation of this in ee physical electronics ... airc it requires a 12 to 15 kv potential difference to generate weak X-rays .... one of those electron volt calculations

"Plunk your magic wand Froggie !"
"Hi ya kids ! Hi ya, Hi Ya !"

"Now sit real close to the screen kids, I'll tell ya secrets."

X-ray heaven for the lil' darlings.

Seriously, the plasma experiment sounds like modulation fun.