[AMRadio] Ranger II Problem ? Need Help..


Jim candela jcandela at prodigy.net
Thu Apr 13 07:36:50 EDT 2006



Geoff,

    OK after re-reading I see the situation is different than what I
interpreted the first read through. If the Ranger blocks the receiver when
in idle mode, then something is oscillating. If so, is it a broadband
emission at a 60 hertz rep rate, or just a spur near the transmit frequency
where the Ranger was tuned up? Why the "loud hum"? A parasitic oscillation
doesn't usually AM or FM modulate itself with 60/120 hz ripple? I bet there
is something else happening here and the RF stages are not being fully cut
off when in receive mode. Sometimes when a transmitter is unloaded, and the
final RF tube is not completely cut-off (grid block keying) the TR relay
needs to also short the transmitter output, or better yet apply a 50 ohm
load. Still, I agree that something is likely awry, and finding that is the
best approach.

    It would be most interesting to use a scope to look at the receiver IF
output to see what is being received.

Jim

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net]On Behalf Of W5OMR/Geoff
Sent: Wednesday, April 12, 2006 4:01 AM
To: Discussion of AM Radio
Subject: Re: [AMRadio] Ranger II Problem ? Need Help..


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??
>
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

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