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 Post subject: Western Electric 92-B Driver
PostPosted: Jul Thu 19, 2018 5:10 am 
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Joined: Apr Sat 18, 2015 3:01 am
Posts: 99
Location: Lexington KY
In the WE 92-B amplifier, would the UTC HA-104 be a good candidate for the 300B driver?
http://bit.ly/2L8DDZN

HA-104 Single Plate to PP grids.


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 Post subject: Re: Western Electric 92-B Driver
PostPosted: Jul Mon 23, 2018 1:14 am 
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Joined: May Thu 24, 2018 11:27 pm
Posts: 34
Location: NJ 08520
It might be...Since the original 285B(?) opened up somewhere (?) and you have an HA-104 on-hand, give it a try and listen...Since you can actually disconnect the first tube gain stage and possibly even the second, hopefully the HA-104 (plus your associated preamp) will provide enough system gain. Also, keep in mind that the fidelity of the UTC tranny actually exceeds the amp's frequency response potential. However, since the amp is cathode biased, parasitic HF oscillations should not be a problem.

If the original interstage opened up on only one side of the secondary, you can rewire the "old radio trick" of installing two, identical resistors in series, across the good secondary winding. The junction of these two "padding resistors" then becomes the "C" (negative bias) or ground connection. I have used this "hints and kinks" trick on many interstage tranny equipped amp stages. I usually use two matched 100K Ohm resistors in series.
If the primary opened, that would be a sorry situation. Since the circuit shows a parallel fed primary, then that "kickback" blocking cap leaked enough DC to melt the fine wire used in the primary...

If the gain with one 262 input/driver tube is inadequate, do you have other interstage trannies to choose ?


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 Post subject: Re: Western Electric 92-B Driver
PostPosted: Jul Mon 23, 2018 1:38 am 
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Joined: Jul Fri 18, 2008 10:02 am
Posts: 2055
Location: near ST Louis Mo 62002
There is no DC current in the primary or the secondary of the driver transfomer so the HA-104 should work well in that circuit .

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Mark
(Conti the brain damaged robot )


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