[Drake] T4XC performance

[Garey Barrell]

Ed -

All typical.   Alignment will correct most. 

The 10M trimmer problem can usually be resolved by tuning the RF TUNE 
control a little further than described in the procedure so that a 
little more capacitance is required.  It also helps to put a dab of nail 
polish on the trimmer adjuster screw.  There is so little tension that 
it is very sensitive to vibration/shock/thermal variation.

The CW GAIN problem is normal, although yours is a bit more extreme than 
most.  Check R104 and R106 value.  Typically 2 - 3 o'clock, although 
sometimes on 10M it takes a little more.  Also, re-peak the TUNE and 
LOAD controls for maximum output as you increase the GAIN.  The TUNE 
GAIN control is a little high (typically 10 - 11 for ALC saturation) 
also, V9 gain may be a little low, and/or C107 ESR a little high.  High 
C107 ESR also usually results in "backwave" on the sidetone.

The AM is OK.  It is purposely kept low to discourage overdriving on 
AM.  There is NO ALC on AM and it is not all that difficult to drive it 
into clipping.  A scope is a VERY good idea.  There is a mod to increase 
this "resting" power, but it defeats the purpose of "controlled carrier" 
modulation, i.e., keeping the "no modulation" dissipation low and 
increasing the carrier only when it is needed to support modulation.  
This modulation method does cause the S-Meter to waver at the other end, 
making it harder to convince listeners that you are "really" running 
AM!.    If they didn't have S-Meters, they'd never know!  :-)

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual
<http://www.k4oah.com>



DJED1 at aol.com wrote:

>I'm working on a T4XC I bought on eBay ("look, excellent"), and found some 
>unexpected problems -I need advice on troubleshooting.   First, the power output 
>was only 25 watts on 10 meters, although sold as "full power out".   I did an 
>alignment and changed the 6JB6s, and now get about 80 watts on 10, increasing 
>to over 100 on 20 and below.   My concern is that the rearmost trimmer on 10 
>meters will not peak, although the trimmer will reduce the power if turned 
>enough.   It's hard to imagine the trimmer is bad.   Any suggestions for further 
>troubleshooting?  Second, I found that on CW I have to turn the RF gain much 
>further than in tune mode to get full power output.   I can tune up on 20 with 
>the RF gain at 12 o'clock, but need to go to 4 o'clock on CW to get full power 
>out.   Is this normal and if not, what do I look for in troubleshooting.   
>Similarly, on AM I get an indication of about 10 watts out, with higher reading 
>when I modulate.   Is this normal?   SSB seems OK compared to another T4XC I 
>have.   I have a pretty good stock of test equipment for troubleshooting.   
>Thanks for the help
>Ed
>
>  
>