I just repaired a Henry 3KA for a friend. It had suffered a sorted tube, and
blew apart the HV current-limiting resistor (25ohm/25w) and plate-current
trip-out adj. resistor. I replaced the bad tube and blown resistors, and the
amp is working normally with 1500w out at 100w drive.
I am noticing that the ZSAC current when set to the SSB position is around
300ma Ip for 4000v Ep, and 150ma Ip for 3400v Ep when set to the CW position.
These levels seem hi for a pair of 500Z's, and when keyed with no drive, the
tubes get orange within 15 seconds or so. The zener diode is rated @ 10v, and
seems to check OK. Is this a result of using Chinese tubes, or normal for a
10v bias diode ?
I know that too low of a ZSAC results in splatter, but other than excess
heat, what is the downside of having a higher ZSAC ?
BTW, filament voltage is around 5.2v , measured at the point the transformer
enters the RF deck. When measured on the transformer side of the choke, how
much higher should I be looking for to result in 5.0v at the tube ?
I appreciate the knowledge available here on the reflector. Even with the
bickering, there is always something new to learn, being a younger generation
ham born in the solid state era!
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