Peter;
The 7 pin gas regulator will sink 30 ma while the larger octal type will
sink 40 ma. Typically a 4CX250 will run 5 to 10 ma negative screen
current, if properly loaded, to 35 ma at 300 VDC lightly loaded. The 7
pin regulators won't handle the current while the octal versions
marginally will. Regulation is not adequate in either case and IM will
suffer.
As a builder of amps using these tubes for VHF I know what a challenge
to get them going and keep them happy. They are very efficient, low
drive amps BUT..... one flash over and it time to get the checkbook.
73
Bob K4TAX (See my call on QRZ.COM)
Peter Chadwick wrote:
>
> It's a bit disappointing that his web site says nothing about real performance
> parameters, such as harmonics, IMD and so on. Also, using gas tube voltage
> regulators for 4CX250 screen supplies has surely been exposed as about the
> worst
> way to go (best part of 15 or 20 years ago) ......and why the octal variety of
> VR tube, not even the miniature 7 pin type?
>
> I can't say that I'm impressed by what is on the web site.....but I'm not an
> amplifier buyer anyway.
>
> 73
>
> Peter G3RZP
>
> --
> FAQ on WWW: http://www.contesting.com/FAQ/amps
> Submissions: amps@contesting.com
> Administrative requests: amps-REQUEST@contesting.com
> Problems: owner-amps@contesting.com
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|