[Drake] TR4CW/rit issues

[Garey Barrell]

Larry -

IF your crackling and noise doesn't increase in volume when you increase the AF GAIN, the most 
likely causes are, in order, V17, C135, C212 and C211.  C136 or C142 are possible suspects, but much 
less likely than the four above.  ALL are located on Board 5, the small board next to the V17 
socket.  My Service CD would be very helpful!  :-)

The low receive sensitivity is most likely the RCVR / TCVR switch on the left side of the cabinet.  
Exercise this and a drop or two of DeoxIT if you have it.  Same for the #12 Fuse Bulb next to the 
relay, pull and re-insert a few times and DeoxIT.  The relay is easy to remove, not so easy to 
replace.  Look carefully at the wire bail to see how it is hooked into the socket, then pry up the 
top side near the hook end until it clears the socket notch.  The relay can then be unplugged.  If 
you look at the relay clear housing, you can see little nubs of plastic in the cover that snap into 
notches in the relay base.  You can  _carefully_  pry the case edge away from the base, (it's 
actually fairly flexible,) far enough to clear the notch, and while holding what you have gained, do 
the same on the other side.  The case will then slide off.   CAREFULLY clean the contacts by 
slipping a small strip of bond paper between the contacts and then withdraw it, holding pressure by 
hand.  If you have  DeoxIT a drop or two on the paper will make this easier, and it will last 
longer.  Do NOT apply too much pressure to avoid bending the contact arms, just enough to let the 
paper scrub the contact surfaces.  Then replace the cover, hook the bottom end of the wire bail 
while you can see where it goes, and then insert the relay and snap the wire bail in place on top.  
This is the hardest part of the job!

73, Garey - K4OAH
Glen Allen, VA

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


Larry Knapp wrote:
> To all those Drake guru's.....I have a TR4CW/rit that has a couple of issues I would like some assistance on.
>   
> 1.  I have what I call 'blow by' when listening using the speaker or heaphones on low or minium volume; at minimum volume I hear crackling and noise,
> then when the volume is increased I also hear signals but the crackling&  noise continues.  I have been told that it could be
>   a bypass capacitor in the receiver audio output area; perhaps C136 or C142, both are .01 mfd.  If this is so, exactly how do I get to them?
> Yes, I do have an original manual.
>   
> 2.  My receive sensitivity to me seems low (now that I have recently been reenergized to use one of my favorite radios) based on the past several years of using
> this fairly 'hot' radio.  The 'perceived' low sensitivity may be based on #1 (above), or perhaps it is a dirty relay.  I see the relay.  It is enclosed in a plastic case held
> by a wire clip.  How do I safely get at the relay contacts without damaging the relay and thus to be able to clean the contacts; to eliminate one of my issues.
>   
> Any assistance will be appreciated.  73, Larry KC8JX
>