[Yaesu] YAESU 2100Z linear

[Billy W. Cox]

Guys (and gals?)

Here is a query from Tommy, EI9BTB regarding tubes for his 
FL-2100-Z linear amp ... Perhaps someone else has been down
this road and knows the answer to his questions ... His email
address is listed at the bottom of the text. He is now "on-line"
with the Yaesu reflector (TU KM9P!) to see this posting ...

Please respond to him and or the reflector, not my 'address'.

73 de Bill AA4NU ... 

and here's his query ... text of 2 messages from EI9BTB follow ...
--------------------------------------------------------------------
I do appreciate your help. There is a problem replacing the existing 
572B tubes in the Yaesu 2100B Linear with the Svetlana 572B tubes.

There is an article in the October issue of "Radcom"stating that 
Svetlana 572B has a slightly higher gain than the original.When 
fitted in the FL-2100,FL-2100B,and FL-2100F linears they sometimes 
oscillate in the standby mode because, as Yaesu has confirmed, the 
cut-off bias is only slightly higher than cut-off. If the amplifier 
'takes off ' as an unloaded TPTG oscillator it can  wreak havoc.  

W6TC bought a used FL-2100B and modified the bias circuit  
incorporating a voltage -doubler configuration  to increase the 
stand-by cut-off bias.  After modification, the amplifier becomes 
unconditionally stable when fitted with the higher -gain Svetlana 
572B.

The Heatkit SB-200 which uses a similar circuit has 100 Volt cut-off 
bias and is stable when fitted with the Svetlana 572B.

It also states at the end of these last paragraphs that this applies 
also to the new Yaesu FL2100Z

This seems to indicate that fitting the Svetlana 572B in the Yaesu 
FL-2100Z is okay and does not need any modification.

However I am not prepared to take the chance without having a more 
definite clarification from Yaesu or from someone who has done the 
replacement in a Yaesu FL2100Z with Svetlana 572B tubes.

I am wondering if you could possibly help re replacing the existing
572B Tubes in the Yaesu 2100Z linear with the Svetlana 572B Tubes.
 
I am not sure if they are a direct replacement.  I have contacted Mr.
Badger of the Svetlana Corporation and he advised that I contact
Yaesu direct.

I have been unable to locate an E-Mail address for Yaesu.

I would much appreciate if you can help me.

Yours sincerely,

Tommy Griffin, EI 9 BTB  (his email is ei9btb@indigo.ie)

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