[Kenwood] TS520S problem

Fri Jun 3 05:56:51 EDT 2011

Hello all,
I've been off the air for a while but am finally getting time to fire up 
the 520 again and work some HF. All the emails I had saved from this 
list were lost a while back due to a unexpected hard drive crash, 
including the email address for the list. Here's the rig problem I've 
run into:
This past Sunday evening, I was doing a little ragchewing on 14.273 with 
a fellow in FL. While I was transmitting, I heard the sound of cracking 
ceramics and started seeing smoke coming from the finals area fan. I 
shut it down and, after it cooled off, pulled the covers off. Both of 
the 10ohm, 1W resistors under the tubes were toasted, one so bad I 
couldn't read the color bands. One was the original resistor and the 
other was replaced a couple of years ago. Visual inspection also found 
a cracked diode on the 14V side of the rectifier board. I have all this 
replaced now and the radio is back in operation.
I tested both tubes and found one that wouldn't even register good or 
bad on the tester. I replaced both tubes with a set of tested good 
6146W tubes I had on hand. I'm puzzled why this happened as I'm sure I 
wasn't over-driving the tubes. I have 980VDC on the top of the tubes 
which seems high to me but I don't know why it is high. Any ideas on 
what I need to check before I start using this 520S on the air again?
Thanks and 73's
Erik
KF4KRK
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