[Collins] Exploding 6146 in KWM-2

Garey Barrell k4oah at mindspring.com
Sat Sep 16 09:40:11 EDT 2006



Dr. Gerald N. Johnson wrote:
> On Fri, 2006-09-15 at 23:43 -0500, Dave, K2DP wrote:
>   
>> Food for thought, anyone have some ideas on why a 6146 would literally explode in my KWM-2 while the rig sits in the receive mode ? That is, other than the fact than the tube date code is "63-30" meaning that it is 43 years old !!!!!! Frankly, at that age, I'm not sure what any tube will do, but I am curious to know if others have experienced a similar type failure. Visual examination of the PA circuit in the KWM-2 and the 516F-2 do not show any visible HV capacitor or high wattage resistor failures. 
>>
>> 73 and keep'em glowing !
>> Dave, K2DP,. St. Louis
>>     
>
> There shouldn't be anything IN a tube to cause it to explode. Its a
> vacuum tube. My guess is that the tube envelope was cracked or a seal
> leaked and it got gassy and since it sits with about 900 volts DC on the
> plate with the cathode grounded, when it got gassy enough it drew enough
> current to heat the gas which then expanded and made the appearance of
> an explosion. Did you happen to notice that the getter deposit (that
> silvery spot on the inside of the glass) wasn't so silvery but had some
> white portions before it blew up? A definite sign of gas. Also the plate
> current at idle was probably rising. What's the history of this tube?
>
>   
Bias supply failure???

73, Garey - K4OAH
Atlanta

Drake 2-B, 4-B & C-Line Service CDs
<www.k4oah.com>



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