[Amps] grounding grids

[Joe Subich, W4TV]

> 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 at contesting.com 
> [mailto:amps-bounces at contesting.com] On Behalf Of Jack Shirley
> Sent: Thursday, July 30, 2009 11:00 PM
> To: Thomas Carlsson
> Cc: amps at 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 at 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 at 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 at 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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> >
> >
> >
> > --
> > Thomas, PY2ZXU/SM0CXU
> > Member of the PW2D Team
> >
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