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Old 17th Nov 2015, 4:08 pm   #1
ukcol
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Default 42E Valve

In this wanted thread Andy (radioman) stated:


Quote:
Originally Posted by radioman View Post
........in the type 42, g3 is connected to the cathode (as normal) unlike the 42E where it's connected to g1......
This is in fact the case as shown here.

I have never knowingly seen this electrode configuration before and would be interested to know what effect it has on the characteristic curves for the valve and in what application(s) it would be used.
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Old 17th Nov 2015, 4:43 pm   #2
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Default Re: 42E Valve

There is (was) a discussion here: http://www.radiomuseum.org/tubes/tube_6f6eg.html

This suggests that it was said to give "higher amplification" but I would guess that as it was not common practice it probably did nothing or worse.
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Old 17th Nov 2015, 4:46 pm   #3
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Default Re: 42E Valve

How odd! Sort of goes against the whole idea of screening anode from grid in the first place, RM also lists the similarly-configured 6F6EG.

The mischievous section of my mind wonders if they were in batch production as pentodes when a patent infringement notice from Philips' lawyers plopped onto the doormat and the base wiring was hastily re-configured... I expect that there's a less exciting but more worthy technical explanation though.
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Old 17th Nov 2015, 8:39 pm   #4
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Default Re: 42E Valve

You may be right: certain US-made Philco radios in the 1930s used pentodes with separate connections (and signal-feeds) to g1 and g3 (usually in the IF amp stages I must admit) and called this a "dual-contriol amplifier" stage.

This could have been a way to get rould Philips patents on 'conventional' pentodes.
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Old 17th Nov 2015, 8:51 pm   #5
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Default Re: 42E Valve

Quote:
Originally Posted by PJL View Post
This suggests that it was said to give "higher amplification" but I would guess that as it was not common practice it probably did nothing or worse.
Thanks for the link Peter; it would be interesting to find an output pentode with a separate pin-out for G3 and compare its curves for normal G3 connection and this G3-G1 configuration.
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Old 17th Nov 2015, 10:30 pm   #6
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Default Re: 42E Valve

6cl6?
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