[AMPS] 4-1000 is this a good tube?+

[Larry Molitor]

At 12:40 PM 5/18/00 -0400, N6BUU@aol.com wrote:
>the above comments reminded me of a fellow I ran into on 40 mtrs a few years
>back he was running 5KV ON A PAIR OF 813s! i wondered, but forgot to asked
>him what his idle current was, as the (2) 813 give only 250 w of plt. dissp.
>anybody here had any experience running 813s at this voltage?? (seems just a
>tad high to me!)
> 
 >
>                          HANK


Hank,

I run 813's at 3000 with no problem, other than taking the usual 
precautions when running a device much higher that the manufacturer's 
suggested ratings. However, recently I inadvertently ran the same amp with 
about 3400 key down volts and had it start to drop output power and 
increase anode current as the tubes got hot. There was no sign of 
"parasitic type oscillation". Switching back to 3000, the amp immediately 
returned to normal operation. I did not have time to analyze the problem as 
I was in the middle of another problem at the time. I hope to get back to 
this when I get time. It would be good to know if the cause of the 
difficulty was the tubes or some other component.

5KV would certainly be an interesting experiment. Rich, have you ever 
hi-potted an 813 at 5 KV?

73,

Larry - W7IUV

>



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