[Kenwood] Help - Removal of 12BY7A in T-599D

[Peter A Markavage]

As an original owner of the 599D Twins, here's how it's done. The shield
is spring metal that holds very tightly around the tube. Grip the tube
and shield and gently rock the tube back and forth while pulling upward.
The strap is attached to the tube socket and is positioned between the
tube and shield. Once the tube pins clear the socket you should be able
continue pulling upward and the strap will slide out from between the
shield and tube. Now, with the tube on a bench or table, with your
fingers, gently pry the long edge of the shield slightly, to loosen the
spring tension on the tube. The tube should slide out with ease or with a
minor push on the tip (tube top). When testing is complete, insert the
tube back into the socket. Then with one finger hold the strap next to
the tube glass and gently slide the tube shield down the tube and over
the strap. Make sure the strap remains straight and does not buckle.

I will "assume" that you have followed the directions in the operating
manual for tuning the rig. If the Driver and Finals testing and/or
replacements still don't solve the problem, check the pre-driver
transistor (drives the 12BY7). Looking down at the 12BY7 in its socket,
the pre-driver transistor is at the lower left about an inch from the
tube. It's the only transistor there that is mounted in a socket. It's a
MOSFET, 3SK22, and due to the heat generated by the 12BY7, will, over
time, degrade drive performance with a loss or lessening of drive to the
12BY7. Additional peaking of the Drive control and increasing the Carrier
Level control can compensate for the deterioration for awhile, but, in
time, it will have to be replaced. 3SK22's are still around; there are
NTE equivalents; and 3N200's or 40673's will also work.

Pete, WA2CWA
FYI: manuals are available from me, www.manualman.com 


On Fri, 14 Nov 2003 18:43:29 -0600 "jdraughn" <jdraughn1@cox.net> writes:
> Good evening all,
> 
> OK I give, how do you get the 12BY7A Driver amplifier
> tube out of the radio. I have not been able to get the
> tube out of the metal shield that fits around the tube and the 
> shield is fastened to the tube socket buy a small strap that's
> too short to allow the tube to be layed over and pushed out.
> 
> What am doing wrong?
> 
> BTW anyone have a copy of the service manual or know of a source for 
> one?
> 
> I can only get about 5 watts out of the rig.
> 
> Thanks,
> Jeff, N0OST