[Amps] sb220 question after mods

[Pete Smith]

A propos of this -- what does it signify if the grid meter reads well below 
zero when an SB-220 is idling at no drive?

73, Pete N4ZR

At 11:31 AM 1/16/2005, Vic Rosenthal wrote:

>N7uvh at aol.com wrote:
>>
>>Hi guys...
>>
>>Been working on a sb220.. did the rectifer and choke mods. Replaced with
>>Harbah parts.
>>I have noticed that i don't have a idle plate and grid currant.
>
>You should never have ANY idle grid current.  If you do, your amplifier is 
>oscillating or something is wrong with the metering circuit.  Zero signal 
>plate current should be about 160-200 ma (for two tubes) for good 
>linearity on SSB. If you are only running CW or RTTY, it will work fine at 
>zero, although it will take more drive.
>
>>i noticed that the right tube will glow some and the  left tube does not.
>
>One is weaker than the other or they are different brands (the Amperex 
>ones have significantly different characteristics).  The one that is 
>glowing is doing most of the work.  They can glow dull red, but if they 
>glow bright orange or yellow, you are exceeding the dissipation 
>rating.  Or, maybe one is a carbon anode type and the other is metal.
>
>--
>73,
>Vic, K2VCO
>Fresno CA
>http://www.qsl.net/k2vco
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