I had a TR-4 once I acqured with the same problem. The calibrator signal
was very strong but the reciever was deaf. Apparently the rig was hit with
a lightning strike and took out the couple turn link from the antenna to one
of the can transformers. (I don't have a schematic in front of me). I had
to remove a coupling shaft to get at the can transformer and remove it and
then remove the can over the RF transformer. The link coil was melted
apart. All I had to do was make a new link, maybe 2 or 3 turns as I recall,
out of magnet wire and reverse the process. My protection lamp also needed
replacing as well as the slide switch. Once this was done, everything
worked just fine.
Lee, w0vt
----- Original Message -----
From: "Paul Gerhardt" <[email protected]>
To: <[email protected]>
Sent: Thursday, December 16, 2010 10:23 PM
Subject: [Drakelist] TR-4 Low Receive
TR-4
TR-4 I am working now seems to have two main 'issues'
1. Low Receive. I have checked and cleaned the antenna relay and
ohming out the circuit it appears to be switching OK. The Cal
Function seems to work normally and according to the schematic seems
to inject the signal to the grid of V7 which is nearly the same point
that the Receive Antenna Signal comes in. The Cal Signal provides a
S9 plus some S meter reading on 40M and plenty of audio to the
speaker. The receive signals are quite weak and even the strongest
signals do not move the meter. They are copyable with the audio gain
up all the way however. The transmitter seems to work normally. Other
bands are pretty much the same with the Cal signal being weaker as one
goes up in freq. The transmitter seems normal.
2. One Xtal filter seems 'dead' only the X position works on any band.
All the tubes have been checked and the V7 has been subbed with the
same result. Transmitter shows good power and modulation on both SSB
and AM (in the X pos)
I am tempted to start trying to align the RF and mixer transformers T9
T10 but I really think there is an open or hi resistance in the RX ant
path. The antenna jack reads a short in the RX position and this
seems to be 'normal' as the coupling to T9 should show only the
resistance of the T9 and the small coax from the Lamp Fuse.
Any other troubleshooting ideas from the group?
--
Paul Gerhardt
K3PG
http://pgerhardt.blogspot.com
QRP ARCI 6674
FP 274
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