[Amps] Drake L4B to 6 Meters Help

[Joe]

This Thread is interesting,
I have not dig into this old beast of a SB-220 yet to remember how or 
what the circuit is composed of. But back in the 80's This SB-220 had a 
mod added that made it run a LOT cooler because even when the amp was 
placed in transmit mode, unless there was watts going in, there was zero 
idle current.

I honestly do not remember exactly how this was accomplished. tho.

Joe WB9SBD
Sig
The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com
On 12/13/2016 1:21 AM, gudguyham--- via Amps wrote:
> Self cut off bias has NOTHING to do with operating bias!  Operating bias is set by Zener diodes or a string of diodes in the CT return of the filament transformer.  The more string diodes or the higher the Zener voltage the lower the idle current.  Zero bias means no operating bias added to the normal current draw of the tubes.  So, remove or short out any zener or string diodes in the CT and allow the amp to idle at its normal zero bias value and watch your output increase.
>
> Sent from AOL Mobile Mail
>
>
> -----Original Message-----
> From: Michelle <michelle_melt at windstream.net>
> To: amps <amps at contesting.com>
> Sent: Tue, Dec 13, 2016 12:51 AM
> Subject: [Amps] Drake L4B to 6 Meters Help
>
>
>
>
> -----Original Message-----
> From: Paul Baldock
> Sent: Monday, December 12, 2016 10:51 PM
> To: Michelle ; <a href="mailto:amps at contesting.com">amps at contesting.com</a>
> Subject: Re: [Amps] Drake L4B to 6 Meters Help
>
> Michelle
>
> Did you say that you are running the 2 tubes a zero bias and have
> about 100mA idle current. I think it should be more like 200mA in the
> SSB position. This would suggest that either your high voltage is
> low, or that one tube is not working/connected. One tube would be a
> good reason for only getting 600W PEP.
> - Paul
>
>
> Paul,
> The 100 ma idle current was due to the "self" cut off bias mod I installed,
> I have since found out 100 ma is to low and
> I am in the process of trying to raise it back up.
>
> Michelle
>
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