[Drake] T-4X info

[Garey Barrell]

Larry -

OK.  There was a field change bulletin issued to replace R95 with a back
panel pot (15M).  (Attached)  Depending upon who installed it, it might
turn either way to increase delay!  :-)   If it is set for minimum
resistance, the results would be as you describe.  If it is all the way
one way, turn it all the way the other!

If the transmitter loads up OK in  _TUNE_  mode, the sidetone oscillator
IS running, and the problem is elsewhere.  Next suspect would be a bad
C144 (10 uF @ 25V) on Pin 3 of V10a (6EV7), - or - possibly open D10,
1N483A diode.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>



telegrapher at att.net wrote:
> Neither of those adjustments make any difference.  BUT, there is a Vox 
> Delay pot on the back and it's labeled as such.  haven't done anything 
> with that yet.
>
> Larry
> W0OGH
>
>  
>
>     -------------- Original message from Garey Barrell
>     <k4oah at mindspring.com>: --------------
>
>
>     > Larry -
>     >
>     > Those two controls are VOX Gain and ANTI-VOX, front to back.
>     >
>     > Start with the VOX full CW and the ANTI-VOX full CCW. Bring up
>     the GAIN
>     > control on the front panel until the plate current kicks up to
>     about 150
>     > mA. Then turn the VOX control CCW for the drop-out time you prefer
>     > between phrases, or ... There is no delay control on the T-4X,
>     delay
>     > being adjusted with the VOX Gain.
>     >
>     > If you can't get what you want in the way of delay, you can
>     change the
>     > value of R95. R95 is the 4.7M (original) across the diode on the
>     VOX
>     > board near C145, the 0.1 uF, 200V film capacitor. The VOX tube
>     is the 6EV7.
>     >
>     > There is a small circuit in the transmitter that sends a pulse
>     to the
>     > relay tube to pull it in FAST to prevent clipping of the first
>     dot or
>     > syllable. The relay is then held in by the sidetone oscillator
>     tone as
>     > long as the key is down. Most likely proper adjustment will
>     solve your
>     > problem. If not, check to see if the sidetone is present.
>     Sidetone is
>     > generated by switching the Mic Amp (12AX7) to a phase shift
>     oscillator.
>     >
>     > If no luck, let us know!
>     >
>     > 73, Garey - K4OAH
>     > Glen Allen, VA
>     >
>     > Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
>     >
>     >
>     >
>     >
>     > telegrapher at att.net wrote:
>     > > I recently came to be the owner of a T-4X. Really nice and
>     looks like the
>     > finals are good also. No documentation. I have the CD which
>     covers the -C-
>     > Line but nothing in there that i swa says anything about the
>     T-4X or B line.
>     > >
>     > > There are two controls on the right side of the transmitter. I
>     don't remember
>     > just what they are but one of them affects the keying of the
>     transmitter. VOX
>     > gain or something. What happens is that when i depress the key,
>     all i get is
>     > just a slight kick of plate current. I'm suspecting that one of
>     those two
>     > controls needs to be adjusted, but which one?
>     > >
>     > > Idle Ip is good and it loads up to full output. Can't ask for
>     better than
>     > that except to fix the keying. Anyone with a manual for the T-4X
>     or T-4XB as i
>     > think they are pretty similar. And, what is the tube that works
>     in that
>     > circuit. Seems it was an odd number type?
>     > >
>     > > Larry
>     > > W0OGH
>     > >
>