Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Wayne -
Certainly could be weak finals. Make sure both are "lit"! :-) Also a
weak driver (12BY7) but less likely. Alignment is also a possibility.
The trimmer adjustments are touchy, particularly on the higher bands. A
simple pass through the alignment procedure in the manual, just peaking
the trimmers, will often bring things back up.
Check R26. It's often damaged by someone using a metal screwdriver to
adjust the trimmers. All it takes is a momentary short from the trimmer
to the chassis, putting the +250VDC supply directly across that 1/2W
resistor!!
Also check R32 and R33 for condition and value, along with R30 and R31.
RF Parts is a good source of matched 6JB6 tubes, albeit a little
expensive. Sylvania (or Zenith) branded tubes are preferred, with RCA
and GE second choice. Other brands may or may not work properly without
adjusting the neutralization capacity beyond the range of the variable cap.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>
Wayne Rogers wrote:
Good afternoon. I'm new to the list.
I've had a T4XB and an R4B sitting on my workshop shelf for way too
long and have decided to bring it back to life. Don't have a lot of
experience with Drake, but do have 40 plus years in the hobby and an
electronics background, though I haven't done a lot of electronics
work recently.
So - I'm starting with the T4XB. It works, but power output is low.
Here's what I get (into dummy load, tuned for max power out, per manual):
Po = 70 W
Ip = 200 mA
Vp = 690 V
Bias = -55 V (70mA resting current)
Looks to me like I need new finals. Am I missing anything? Want to
be certain. Also, can someone recommend a reliable source for 6JB6's?
Thanks & 73,
Wayne N1WR
Lusby, MD
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