Let's re-read the original message, *carefully*, shall we?
Mark said:
Hello All,
I have a Ranger II that's problem is a very loud hum, seems like 60 Hz, heard in
my receiver, that comes from the ranger.. The transmitter tunes up fine, and
modulation is O.K. It **isn't** there when the transmitter is zeroed into the
receiver, just when I *//remove//* the zero.. Completely wipes out the
receiver..
I use the same cables, coax, mic, etc.. on another setup and it works fine,
so I've at least eliminated that.. Sounds like a capacitor not working??
anyone experience this before..Where do I start??
(emphasis mine, to help illustrate)
someone else wrote:
I don't have a Ranger, and never did. Other ranger experts out there
have flooded you with a bunch of good ideas, with maybe one important
exception. When you monitor yourself with a receiver, you often hear hum
when the transmitter is hum free. This is because of ground loops in the
particular set up.
It's not when -transmitting- ... it's when recieving and the Ranger is
idle, and generating the hum, UNTIL he put's it in either xmit, or uses
the Zero-beat function.
I maintain that he's got a driver/buffer combo that's going into
oscillation. I have that same problem happening on another Viking II I
have here, if things are not adjusted correctly. In fact, I've had
reports of being heard on 3.900Mc while transmitting on 3.880. It's a
little birdie that's getting generated in the exciter, and then being
amplified (reduced by 20 or 30db from the fundamental) and appearing
20kc up the band, and lord knows where else. I don't use that exciter
any more..
I learned a long time ago, you just don't peak oscillator and buffer
controls on an old rig like a Viking II or a Ranger, or any of the other
old tube rigs. The buffer plate needs to be dipped while observing the
current on it's metered positoin, and the oscillator needs to be dipped
in much the same way in IT'S metered positoin, then LEAVE 'EM ALONE!
When those conditions are met, -THEN- adjust the grid drive to 5mA
(6146's x2) and let it go. Peaking the oscillator and buffer stages
while looking at the grid current meter is probably what got me (and
maybe others) in trouble on the other Viking II, or other older rigs
that were tuned up improperly.
MY suggestion would be to check/change all of the associated descrete
components associated with the oscillator stage through the grid stage
of the 6146 on the Ranger, Mark, as well as change the tubes out. Not
sure what's in there.. 6AU6 and a 6C4 comes to mind, but it's been
-eons- now since I was in a Ranger. The main thing to remember is, that
these rigs are (as someone else pointed out) 50 years old, and component
values change.
--
73 = Best Regards,
-Geoff/W5OMR
