[Boatanchors] Confussion

[The Pollacks]

I think someone is confussed over how to spell confusion....

-----Original Message-----
From: boatanchors-bounces at mailman.qth.net
[mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Barrie Smith
Sent: Sunday, August 08, 2010 4:32 PM
To: Boatanchors Mail List
Subject: [Boatanchors] Confussion

I got the push-pull pair of VT-127As neutralized, I think.

I then tried increasing the drive, with no HV.  As I increase the drive the
grid current goes up until it reaches 105 ma, which occurs at about 50 watts
of drive.  Increasing the drive beyond that point causes no increase in grid
current.

According to the only specs I have for the tubes, I will need 140 ma of grid
current for the two tubes.

I'm thinking that the grid circuit is fighting itself.  With no safety bias
applied, the bias voltage rises with increased drive.  At 50 watts drive the
bias voltage is -550 volts.

That's 180 volts more than the tube specs call for.

The tube specs call for a 5000 ohm grid resistor, which is what I have
(actually two 2500 ohm in series).

I believe that if the bias voltage were not so high I could achieve my 140
ma of grid current with the 50 watts of drive, which, according to the tube
specs, is what I need.

Any thoughts as to what I should do next?

73, Barrie, W7ALW
______________________________________________________________
Boatanchors mailing list
Home: http://mailman.qth.net/mailman/listinfo/boatanchors
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Boatanchors at mailman.qth.net

List Administrator: Duane Fischer, W8DBF
** For Assistance: dfischer at usol.com ** 


This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html