[Amps] 4CX1600B

[rlm]

>Rich Measures writes:
>> - - -   Does the circuit in which the 4cx1600 is used have a grid 
>> terminating R?  If so, is there an inductor in series with said R?  If 
>> so, how much L?  tnx.
>
>Hi Rich

Hello, Rich, de Rich. 

>It looks like Ray, QRO, added the resistor after 1995 as a mod. It
>also has an inductor in series but the value is not marked in the drawing.
>Why do you ask?

***   - - Because an inductor in series with the grid terminating R does 
three things:
the good:  1. Reduces 10m SWR by cancelling grid XC with XL.
the bad:   2.  Increases level of anode to grid VHF feedback signal 
arriving at grid.  
the ugly:  3.  regeneration may take place, usually during a contest, of 
course.
-  Note -- the source of the VHF feedback signal is the damped-wave 
ringing which takes place at the anode resonance when anode current 
increases or decreases.
-  Thus, it may be that the bang was the end result of a regeneration at 
the frequency of the anode resonance.  This resonance can be measured 
with a dipmeter on either side of the DC-blocker-cap.   The reason for 
the bang is that VHF is blocked by the low-pass HF tank, so it has no 
place to go, runs amuck, and a HV-to-gnd arc may take place..  

>
>Point of interest about converting these amps to a pair of 4CX800's:
>
>Very easy to do as the sockets are mounted on an easy to remove plate.
>However, I have both flavors of Ray's amps and a pair of 800's are 
>NOT the same as one 1600. Not by a thousand watts. 
>
>Both the QRO 2500 (2x4CX800A) and 3K (4CX1600B) amps run
>1500 watts out all day and are fine contest amps so the day I do 
>have to convert the 3K's to 2500's will not be too painful, just sad.
>
>73 Rich KL7RA 
>
>