Simplified G2 Regulator for a 4CX250B amplifier
 

Hi All,

I have been toying with the idea of building a 4CX amp for some while
now but keep being put off by the relative complexity of the protection
circuitry associated with G2.

I (think) that I have read cover to cover the G3SEK and GW4FRX articles
on the subject, and hope that I have ended up with a usable if not
simplified version of the work done by G4JZQ.

I am not trying to compete with any of these guys, I am just trying to
offer another view on the subject.

Take a peek
http://www.geocities.com/markaren10/..._Regulator.pdf
and let me know your thoughts.

This is about 2 hrs work from "engage brain" to "publish first ideas
for comment" so don't be too harsh.

Regards,

Mark.

Simplified G2 Regulator for a 4CX250B amplifier
 

What are you trying to do?


TR1 looks like a current limiter for the FET. Why are you doing that?

The source voltage looks like 425 volts, the series resistor 10k 2W,
the shunt regulator threshold 340-350 volts.

that's about 75 volts differential, so the 10k would have about 7.5 mA
of current. If the screen loaded more than 7mA it would fall out of
regulation.

The FET dissipation would be 2.5 watts assuming no negative screen
current.

What holds the screen to ground when the overload opens?

Why is the VDR on the screen side of the screen current meter?

Maximum screen dissipation would be around 21 mA when the screen was at
about 200 volts. Maximum screen current about 40mA.

73 Tom

Simplified G2 Regulator for a 4CX250B amplifier
 

Hi Tom,

"I have been toying with the idea of building a 4CX amp for some while
now but keep being put off by the relative complexity of the protection
circuitry associated with G2"

Basically, just simplification. See
http://www.ifwtech.co.uk/g3sek/board...ode-manual.pdf for
the whole of Ian's manual (chosen starting point)

There is a bunch more protection stuff on the base of the tube, I
forgot to mention this in the posting. I should have also said that the
starting point for the review should be topological.

I will look at your detailed comments when I wake up (it's 3am :).

Thanks very much for taking a look.

Regards,

Mark.