World of Ham Radio 1997/WOHR97_AmSoft_(1997-02-01).iso/mods/kenwood/ts/ts830_0.doc

Text File | 1997-02-01 | 2KB | 35 lines

That poor little 12BY7 !!  Kenwood doesn't have to buy tubes for replacement
I guess !!   While aligning my rig, I happened to notice the 12BY7 getting
very hot. (Ouch, burnt my finger)  I slipped the shield off and noticed that
the plate gets a little cherry after a few minutes of idling with no drive.
Granted, this isn't normal operation.  After all, most of the time we are
jabberin' away.  However, referring to my trusty tube manual showed that the
screen of the tube was being over-driven even when there was drive present.
Here's a simple fix that should add years to the life of the tube.

Change R37 1/2W Metal-film 3.3K   to   1/2W Metal-film 4.7K

This resistor is located on the RF unit P.C. board which is accesible from
the top of the rig.  I just clipped one lead of the existing resistor and
added 1.5K in series. ( Actually 4.8K in my unit now ).  You will find R37
just to the right of the driver tube, in front of connector 9.

I notice no difference in the operation of the rig on any band, so there is
still plenty of drive available to the Finals.  The tube still runs a little
warm, probably due to the fact that there is also far too much plate voltage
on the little guy.  Stay tuned for another installment, as I'm working on
this at present.

If you operate any of the heavy duty-cycle modes, ( RTTY, etc. ) you might
also want to speed the fan up a little while you are in there.  Move the
wire to the fan from the 100 Volt tap on the power transformer to the 120
Volt tap.  This adds very little extra fan noise, and a little extra air
flow.  I've been running mine this way for over two years now and the fan
motor doesn't seem to be suffering.

Any questions, comments, flames ??

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73 de Jeff WR2E @ KB1BD.nj.usa    Tinton Falls, NJ  07724       Mailbox: WR2E-15
 on 145.07   ----------------------------------