On Fri, 17 Oct 1997 13:03:36 -0500 philk5pc@connect.net (Phil Clements)
writes:
>At 09:30 AM 10/17/97 EDT, you wrote:
>>
>>On Fri, 17 Oct 97 03:15:03 -0800 Rich Measures <measures@vc.net>
>writes:
>>>> at 10:00 PM 10/16/97 -0700, you wrote:
>>>>>I question the resoning on a high value such as the 50ohm 50 Watt
>>>>>resistor in their amp. Seems a little off to me.
>>>>>
>>>>>Comments?
>>>>>
>>>>
>>>>That is Svetlana's recommended value for that tube.
>>>
>>>Which tube, Phil?
>>
>>
>>For the 4CX1600B as used in the Emtron the "real" Svetlana
>recommendation
>>is 25 Ohms or more. This would then lead to the assumption that the
>tube
>>manufacturer feels a 110-120A surge is acceptable at a nominal
>>2700-3000VDC.
>
>I do not! I have to pay "retail" for my tubes.
The last time I looked so do I. I just do not subscribe to the ham myth
that 2X or more overkill is worth anything. Having spent beaucoup years
in the Mil-Industrial world I tend to feel that manufacturers specs on
hollow state devices are well within reason.
The main problem is that most hams and some manufacturers either cant
read or cant understand the specs.
>
>>See my other post for the spec sheet quote.
>>
>>Again assuming around a 3KV Ep in the Emtron (Tube max is 3.3KV) the
>amp
>>designer is being quite conservative with a 60A rating.
>
>It is always best to be conservitive. Most modern day designs are
>hanging
>on the
>ragged edge on component parts at the 1500 watt level.
I agree with many...not most.
>>>>You never want this resistor to open during an event.
>>>
>>>good point -- or sustain any type of damage.
>>>
>>>>10 ohms is ok up to about 3 kv. I am running 20 ohms
>>>>on my Alpha 77SX with good results.
>>>>
>>>Does 'good results' mean that you shorted the anode supply and the
>20
>>>ohm glitch resistor was able to handle the resulting current without
>
>>>sustaining damage?
>
>That is correct...I use 2 10 ohm 12 watt glass wirewounds in series
>due to a
>space constraint. Flashovers in the Alpha 77SX RF compartment have
>been so
>intense that some users have reported that internal parts in the
>blower
>were even destroyed.
The 77SX is probably one of the worst examples that was produced. It
started off bad and the hams and aftermarket types made it worse. It
reminds me of the Edsel...lots of style and a big name
but.......................So much good and bad residing in one box.
73 Carl KM1H
It is imperative that a glitch resistor be added
>in
>the Alpha 77 series. I put the resistor right next to the HV crowbar.
>
>
>(((73)))
>Phil, K5PC
>
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