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Class B 811A Modulator driver




 
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Author Topic: Class B 811A Modulator driver  (Read 1609 times)
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kc2we
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« Reply #25 on: June 15, 2020, 11:03:01 PM »

RCA Ham tips

https://worldradiohistory.com/ARCHIVE-RCA/RCA-Ham-TIps/RCA-Ham-Tips-51-Winter.pdf

Uses 6SJ7 6SN7 6SN7 (2) 807's (2) 811A's. Uses driver transformer. Classic circuit. 300 + watts out. However, if there was a class AB1 option using tubes other than 811's, maybe can do with no transformer.
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Seth Taylor
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« Reply #26 on: June 16, 2020, 09:29:11 AM »

Seth, we just discussed and presented roughly 3 main methods of driving any tube
into Class B2, but in particular the 811 without a transformer?

No transformer is ever needed for AB1, as it is cap coupled.  Cool

                      _-_-bear

PS. Getting "300 watts" out of a pair of 811s, even given the 1250vdc B+ is a tad
optimistic, imho. Maybe peak??. But don't try a sinewave at that power level.
Of course back then 811s were easy to find, and cheap. WWII surplus...
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_-_- bear WB2GCR                   http://www.bearlabs.com
Steve - K4HX
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« Reply #27 on: June 16, 2020, 11:07:52 AM »

Bear, 811s or 811As?
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WBear2GCR
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« Reply #28 on: June 16, 2020, 11:04:17 PM »

Steve, if ur referring to the Ham Tips article? Did not notice.

The 811A is the one found most often today, and it does handle a bit more
power. Other than that the same tube.

But you can drive any tube with one of the cathode drive schemes, just set the
bias through the CT of the choke, or the point inbetween the resistors... etc.

Is that what you were asking?
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Steve - K4HX
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« Reply #29 on: June 19, 2020, 12:47:42 PM »

Yes, the 811A has more plate dissipation. If it's not emission limited, they should be able to produce more power.
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W2PFY
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« Reply #30 on: June 27, 2020, 07:28:03 PM »

To K4HX

Quote
Good stuff Terry. Thanks for sharing.

Your very welcome and judging from the number of downloads, some may be on their way building a cathode follower Grin Grin
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