> This was done to match the output power of the TR-3 and TR-4.
This would also indicate a value to removing the negative feedback
circuit with modern 100 Watt output solid state transceivers. With
their three finals, the TR-3 and TR-4 were capable of 150+ watts
output and the L4/L4B were designed when 1000 Watts plate input was
the rule.
73,
... Joe, W4TV
> -----Original Message-----
> From: amps-bounces@contesting.com
> [mailto:amps-bounces@contesting.com] On Behalf Of Jack Shirley
> Sent: Thursday, July 30, 2009 11:00 PM
> To: Thomas Carlsson
> Cc: amps@contesting.com
> Subject: Re: [Amps] grounding grids
>
>
> The answer is:
>
> to provide -2db negative feedback. This was done to match the
> output power of the TR-3 and TR-4.
>
> Also of note; it was the first 3-400/500 amp to have tuned
> input circuits,
>
> The output circuit was designed to match a 2 : 1 SWR at all
> impedance's and phase angles.
>
> He also designed the MN-2000 which will match a 5 : 1 SWR at
> all impedance's/phase angles.
>
> At one time they were getting L-4s in for service which had
> the pi wound grid chokes where the windings were " slammed
> together" .. This was from plasma arcs inside the tube going
> thru the grid. He called EIMAC about this and they said when
> the 3-500z are being vacuumed sealed, they put high voltage
> on all the terminals to burn off the metal whiskers which
> form during the process. Eimac said " guess we will have to
> let them burn off longer " . After that the problem went away.
>
> The cost of a 3-500 was 24.50 then.
>
> Any other questions?
>
> 73 Jack N8DX
>
> On Thu, Jul 30, 2009 at 10:00 PM, Thomas Carlsson
> <thomascarl@gmail.com>wrote:
>
> > Interesting addition: LK-500 and its brothers have Grids direct to
> > Ground, no components. Cathode resistor only 0.15ohm/3W. SB220 and
> > L4(B) both 1ohm in cathode and they have the same grid
> components, on
> > schematics I have the RFC and C's are copies of each other. 73,
> > Thomas, PY2ZXU/SM0CXU
> >
> >
> > On Thu, Jul 30, 2009 at 8:25 PM, Jack Shirley <jcshirle@gmail.com>
> > wrote:
> >
> >> I looked at the various 3-400 and 3-500 circuits in the
> Eimac Amateur
> >> Service Newsletters and did not find this mentioned anywhere.
> >>
> >> If the SB-220 and L4 use the same grid circuit, I could ask the
> >> engineer who designed the Drake L-4 as I know him personally. Any
> >> interest?
> >>
> >> 73 Jack N8DX
> >> On Thu, Jul 30, 2009 at 6:48 PM, Ward Silver <hwardsil@gmail.com>
> >> wrote:
> >>
> >> > > perhaps somebody with an SB-220 and a spectrum
> analyzer needs to
> >> > > do an IMD profile using each grid circuit and SEE which one
> >> > > produces the cleaner output.
> >> >
> >> > What?! And ruin a perfectly good thread?
> >> >
> >> > 73, Ward N0AX
> >> >
> >> > _______________________________________________
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> >> > Amps@contesting.com
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> >> >
> >> _______________________________________________
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> >>
> >
> >
> >
> > --
> > Thomas, PY2ZXU/SM0CXU
> > Member of the PW2D Team
> >
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