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In the last days, I had an
intresting experience, that could be useful for all Drake
enthusiasts;
Take a TR4C and put inside 3 brand new
6Jb6, then connect it to a supposed well working AC4 ( the AC4 has the bias
supply defective, but you don't know this). Switch the radio on, and while you
wait for warm up, answer to a 10 minutes phone call, or better have a drink of
your choice in the kitchen. When you come back,you will discover that the TR4 is
in tx, the final is drawing all the current possible ( of course without load
connected and not tuned up) and your expensive triplett of new 6JB6 is
good as target for shooting with a slingshot or an air rifle!
Yes, if the negative bias fails, ( - 20 V
instead of - 60 circa ) this is what happens if you are not present, and notice
that the radio goes in TX instead of RX at power-on.
A stupid 20 cent. capacitor can make a
multidollar damage.
I suppose this happens with T4 series
too, so my suggestion is to change the diode and the caps on bias line as
default in the AC4
Good time to all readers!
Carlo Bianconi IK4ISQ
Italy
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- [drakelist] How to ruin a 6JB6 triplett carlobianconi
