Subject: Re: [AMPS] How To Design HV Glitch Protection Circuits
> While Eimac suggests a value of R in the screen ckt, experience
> indicates that a value of R in the screen ckt during a flashover will
> allow the screen voltage to ramp above the rating of the screen bypass
> capacitor. My experience is in VHF and UHF using the 4CX250 and 4CX300
> tubes. Thus sockets with screen bypass capacitor built in is
> necessary. The end result, get the check book out, cause a new socket
> is needed.
>
> 73
> Bob K4TAX
I have found Harris to be very innovative in their designs of broad-band no-tune
high powered amplifiers. Such as plate chokes with no resonances, etc.
A very nifty solution to your problem is also included in the RF-110A amp
that uses a pair of 4CX1500B's. It consists of an SCR, four diodes, and three
resistors. They call it an arc suppressor. When there is a very momentary arc
between the plate and screen the arc suppressor protects the screen power
supply components in the event of such an arc. When an arc occurs, the
current passing through the screen regulator diodes causes a voltage drop
across a resistor which fires the SCR. This shorts to ground two points:
1. The final amplifier screens at their sockets.
2. The highest voltage point on the screen supply.
This shunts the arc currents around the screen supply components to
ground, and shunts the screens of the tubes to ground.
I hope this is helpful to you tetrode folks.
(((73)))
Phil, K5PC
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