>
>
>Conrad Writes ...
>
>>
>>
>> Rich wrote
>>
>> >>Transistors that C/E short offer zero protection.
>>
>> Ok so sense the voltage drop across a resistor across the screen supply,
>> feed the transistor via an opto isolator,make the transistor trip a fast
>> relay in the primary of the supply transformer.This is better and more
>> reliable than a fuse surely.
>>
>
>Make that trip a fast zero crossing solid state relay in the primary
>of the screen supply. The SSR should "open" at the zero voltage point
>and, with the proper MOV to limit the inductive kick-back spike, should
>be the quickest, most reliable protection.
The screen in an 8171 is rated at 275w. Instanteous protection would
interfere with tuneup. A fast acting fuse works. .
>Frankly, I would sense screen
>current, screen voltage, as well as plate current and trip both the
>plate and screen supplies in the event of a fault. I might even use
>a big SCR (screen) or triggered spark gap (plate) to discharge the
>supplies to limit the fault (if I could justify the CO$T).
>
Glitch resistors work well enough. More complicated is not mo betta.
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|