The 425 is a very easy amp to drive....30-35 watts for 1500 out
normally. One way to insure long tube life is to make certain that the
grid overdrive LED on the 425 just flickers once in a while on either
ssb or cw. It is a very conservative measure and thus if you keep that
LED dark you will not overdrive the amp. Tune for maximum po, keeping
Ip such that you aren't going over 1500W out and operate.
I have multiple power meters here and in a few cases three of them on
the same line (digital for power out and swr protection, analog to help
tune the tuner and one in the amp). They never ever agree but that does
not bother me....its all relative anyway. 73 bob de w9ge
Jim Brown wrote:
>
>
>
>
>>Here is what was found to be the problem. The coasx going into
>>and out of the input low pass filter board uses tho9se el-cheapo
>>japanese connectors. found the center conductor of the miniture
>>coax is used a "plug-in" pin into the pcb of he input filter.
>>Guess over time corrosion got the best of it. I soldered both the
>>input and output coax lines (center conductor) to the pc board
>>and mhy problem went away: 1500W out without exceeding the max
>>grid current.
>>
>>I purchased a pair of new tubes, 3CPX800A7 tubes because I
>>thought tubes were flat: NOPE. Now I have spare set of tubes,
>>NOT FOR SALE.
>>
>>
>
>73,
>
>Jim Brown K9YC
>
>
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