>
>
>Hello
>I think and hope that my problem with parasitics in FL-2100B is now solved
>with the help from this AMPS-reflector.
>From Rich Measures, AG6K I got some useful advice and a suppressor kit for
>2pcs 572B´s.
>Here is what I did:
>
>1. Anode circuit
>¤ 2 NiCr suppressors installed in each anode.
>6 turns in parallel with 100 ohm 3Watt Metal Oxide Film resistor (MOF)
>¤Original silvered strap from C-blocking to C1-tank replaced with 2 NiCr
>wires, one straight, the other with 1 turn 6mm diameter.
>After these modifications no VHF-resonances could be detected. Before I had
>a well-defined dip around 105 MHz.
>
>2.Grid circuit
>¤ 200pF decoupling conds replaced by 2x470pF from each grid directly to
>ground lug at the socket mounting screw.
>¤ Original 33 ohm grid resistor removed and replaced by 33 ohm and 10 ohm
>in series. 10 ohm to grid. On each wire of the 10 ohm resistor I placed a
>ferrite bead, my=125, mix 61. Resistors are 2W MOF.
>
>3. Cathode (filament) circuit
>¤ From input network switch to each filament I used 10nF in series with 10
>ohm 3W MOF.
>
>4. Misc.
>¤ Glitch protection diodes installed in parallel with plate meter "shant"
>R3. 2 diodes type 1N540x in series, anode to ground.
>¤ Filament voltage now 6,0VAC at socket. In my case I used the 234v tab on
>the primary of T1. This to increase tube life.
>¤ On all bands I have 500+ Watts with the amplifier driven to 400mA.
>
>I am gratefull to Rich, AG6K for his advice and help. I think Rich has made
>a great contribution towards our better understanding of VHF-parasitics.
>
>73
thanks much, Hans. Please say hello to aunt Marta when you see her.
Cheers.
- Rich..., 805.386.3734, www.vcnet.com/measures.
--
FAQ on WWW: http://www.contesting.com/ampsfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|