Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Doug -
First step is to put the 160M crystal back in the receiver, and check
the operation in transceive with receiver control. If this results in
the same failure, you have just eliminated all of the circuitry
associated with the Band Oscillator, PTO and Premixer stages in the
transmitter.
There are very few components peculiar to 160M.
Each of these components has an associated bandswitch contact, and while
it doesn't appear to be related to the switch contact itself, it IS
quite possible to be a "cold" or "rosin" solder joint on the switch contact.
C36, C37 and T1
C53, C54 and T9
Less likely ...
C86 and C193
C89
C45
So my process would be to physically examine each of these components
and their associated switch contacts for solder integrity. Cold spray
might expose a bad connection, but it's probably not a bad component.
T1 and T9 are small solenoidal coils mounted right on the bandswitch
contacts.
Putting on my Swami hat, I'm gonna guess T9 solder is the culprit.!
This is based partly on the fact that it's probably the most difficult
item on the list to access, but also that if this connection goes open,
it removes the plate voltage from the 12BY7 driver stage.
Let us know!!
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>
Doug Smith wrote:
Doug Smith <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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On Thu, 2007-11-29 at 20:08 -0700, Doug Smith wrote:
Doug Smith made an utterance to the drakelist gang
I'm going to try moving it to the T-4XC to see if that makes a difference.
OK, I've put the 160 meter crystal in the T-4XC and I'm seeing the same
results as when it was in the R-4C. No output (well, about 1 watt) on
transmit but excellent reception. I tested with the TRANSCEIVE switch
in both XMTR and SEPARATE modes and got the same symptoms.
Switching the crystal to the T-4XC eliminates the receiver as a possible
problem. And the problem does only occur as the transmitter warms up.
I get normal operation on all other bands so I can't believe it's a
tube. And, the crystal is oscillating since I receive good signals on
160.
I've put the T-4XC on the bench and put my 'scope on pin 2 (grid) of the
6EJ7 premix tube and temporarily grounded pin 3 (cathode). I see -0.93
VDC with any crystal (including the 160 meter crystal) and -1.04 VDC
with the VFO. I'm thinking the crystal is OK.
The symptoms are normal power output on 160 for a minute or two after
initial turn-on, then power output drops off to near 0 watts and does
not return until the rig has been allowed to go completely cold.
Operation on all other bands is normal.
I'm stumped...
73,
-Doug, W7KF
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