ken scharf wrote:

A better way to use the 813 in triode mode is to connect the two grids
together. This creates a HI-MU zero bias triode.

That is the way I am using them. Got it all together last night and had
a short QSO with a good audio report. It takes very little Ranger
audio to get 100% mod.

Unfortunately, the plate tuning cap started arcing so I had to shut it
down and have a look today.

js

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Jack Schmidling wrote:
ken scharf wrote:

A better way to use the 813 in triode mode is to connect the two grids
together. This creates a HI-MU zero bias triode.


That is the way I am using them. Got it all together last night and had
a short QSO with a good audio report. It takes very little Ranger
audio to get 100% mod.

Unfortunately, the plate tuning cap started arcing so I had to shut it
down and have a look today.

js

Please post a schematic on your web site!

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Feb 23, 10:52 am, Tim Wescott wrote:
Please post a schematic on your web site!

Tim -
You might be surprised how few parts there are in a classical zero-
bias class-B modulator.

There's a schematic in the 50's/60's ARRL handbooks, and the ENTIRE
circuit is two 811A's and an output transformer. That's it!

This simplicity is the cunning advantage and popularity of zero-bias
triodes (or zero-bias-triode operation of the other tubes). Once you
get to beam tubes/pentodes with all their bias supplies and screen
supplies and power-supply-sequencing etc. you start getting into
having to draw schematics.

Later editions added a pi filter on the output to reduce "splatter"
and a control relay to remove plate voltage on receive.

Tim.

Tim Shoppa wrote:

On Feb 23, 10:52 am, Tim Wescott wrote:

Please post a schematic on your web site!


Tim -
You might be surprised how few parts there are in a classical zero-
bias class-B modulator.

There's a schematic in the 50's/60's ARRL handbooks, and the ENTIRE
circuit is two 811A's and an output transformer. That's it!

This simplicity is the cunning advantage and popularity of zero-bias
triodes (or zero-bias-triode operation of the other tubes). Once you
get to beam tubes/pentodes with all their bias supplies and screen
supplies and power-supply-sequencing etc. you start getting into
having to draw schematics.

Later editions added a pi filter on the output to reduce "splatter"
and a control relay to remove plate voltage on receive.

Tim.

I guess I'm more interested in knowing what the supply and grid voltages
are, transformer ratios, a bill of materials, that sort of thing.

Yes, you are correct that the schematic of a one cubic foot, 100 pound
monster amplifier could be drawn on a business card, but still...

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Feb 23, 12:30 pm, Tim Wescott wrote:
I guess I'm more interested in knowing what the supply and grid voltages
are, transformer ratios, a bill of materials, that sort of thing.

I too am interested in the transformers that he's using. Tubes are
easy to come by in comparison to appropriate modulation transformers.

And it can't be the super-simplest implementation because I see some
pictures with little power transformers with diodes and electrolytics
forming some kind of bias supply.

Then you have to work hard to not burn up your favorite modulation and
plate transformers :-). Plate chokes, I can rewind them when they
catch on fire now!

Tim.