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[AMPS] failure

To: <amps@contesting.com>
Subject: [AMPS] failure
From: measures@vc.net (Rich Measures)
Date: Wed, 18 Jun 97 08:48:40 -0700
>> From:          Peter Chadwick <Peter.Chadwick@gpsemi.com>
>> To:            amps <amps@contesting.com>
>> Subject:       [AMPS] failure
To: <amps@contesting.com>
>> Date:          Tue, 17 Jun 97 14:04:00 +0000
>
>> I think the 8122 has a cathode rather than a filament, so my guess is
>> that it drew a lot of current while the cathode cooled down, which takes
>> some time. ..
..........snip.....
>Turning off the filament and bias and leaving the anode on will 
>most likely ruin a metal oxide cathode tube. >If the cathode 
>isn't stripped .....

Cathode stripping seems quite likely.  This problem can be avoided by 
designing the amplifier so that when the heater voltage drops just below 
the rated minimum, the electric-mains power contactor opens.  This can be 
accomplished with a 723 comparitor IC and an optoisolator.  



Rich---

R. L. Measures, 805-386-3734, AG6K   


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