[Kenwood] TS520S problem

[Rob Atkinson]

The bad 6146 could have been the problem.    What load impedance is the rig
working into?  do you have it tuned up right?  (these days not everyone
knows how to tune up a tube rig.)  Another long shot:  What's your line
voltage?   What was the 520 designed to run on?  If 115 v. and yours is at
125 say, that might be a cause of problems over the long term.

73

rob
K5UJ

On Fri, Jun 3, 2011 at 4:56 AM, Erik Iddings <erikwiddings at embarqmail.com>wrote:

> 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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