[Drake] TR4C repairs

[Garey Barrell]

Bill -

You need to check your meter shunt resistor, R45.  It's gone up in 
value, causing your PLATE meter to read high.  This is a little more 
than reasonable efficiency calculations, as it also makes you set the PA 
idle current too low, affecting linearity.

When you change R45, you'll also probably need to select a new R13 to 
ensure that the PLATE meter reads 100 mA accurately.  Easiest is to 
measure the new R45 with your DMM, then calculate the voltage drop for 
100 mA of idle current.  Set that current by adjusting the BIAS supply, 
and then select R13 so the PLATE meter reads 100 mA.

While you're in there, you might also want to check R93, R167 and R121 
for value and condition.  These also tend to go up in value.

73, Garey - K4OAH
Glen Allen, VA

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


wabate wrote:
> Dick,
>
> XMIT gain 9:30
> Plate     7.5
> Load      2.5
> RF tune   5.7
> Output    150 watts,
> Current   440 ma
>
> Could tune up to about 175 watts but then current would be over 500 ma.
>    Hope that helps.  I'm trying to preserve my sanity too.  Lost the slug
> on L7.  Know its on the floor somewhere!!!  HI HI..
>
> GL,
>
> Bill, K3PGB
>
>
> Dick KF4NS wrote:
>
>   >  For the moment I will not say much, just a request before anything
> further. I am trying to keep my cool.
>   >
>   >  Would someone please try something for me on a good working TR4C?
>   >
>   >  Connect a dummy load, no mic no key plugged in.
>   >  Set the VFO for 14.260mhz and tune up for max power out as read on a
> decent wattmeter (not relative power on the S meter).
>   >  Use the X-CW mode and  SIDEBAND X.
>   >
>   >  Then let me know the XMIT GAIN clock position, the PLATE, RF TUNE and
> LOAD numerical knob setting, output watts and plate current.
>   >
>   >  I am trying to maintain my sanity but not sure how long I can last.
> Enough for now.
>   >
>   >  Thanks and 73, Dick KF4NS
>   >  St Petersburg, FL 33714 USA
>   >  Keep The Glow!
>   >
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