|[AMRadio] Ranger problem-No joy yet|
Tonne at Comcast.Net
Wed Jan 1 12:24:50 EST 2014
Bob and all:
I have again run the analysis but this time put the
Key Up and also the Key Down voltages on that
It is again posted (case-sensitive if you do it manually):
Note that all of the voltages except the actual VFO blocking
signal are based on a negative 56 volts out of the bias
circuit. So if you measure, say, -60 volts there then all of
the voltages will be a bit greater than the schematic shows.
For those that can't get the schematic, here is a table of
Bias voltage (one end of R42): -56
Junction of R42 and R43, grid of a 12AU7: Key up=-43, Key down=0
Junction of R43 and R45 (multiplier blocking): Key up= -38, Key down=0
Junction of R44 and R45 (buffer blocking): Key up=-30, Key down=0
Voltage at top side of C86: Key up=-38, Key down=0
Hope this helps you home in on what is going on.
- Jim Tonne W4ENE
On 1/1/2014 8:40 AM, Robert Sauvan wrote:
> I cant thank everyone enough for the suggestions to my fix on the
> Ranger. I have gone through everyones suggestions with no success yet.
> All caps check out good, C86, C87, & C89. R39 is the variable resistor
> to set the keying and that shows to be working on the scope,but, it
> doesnt seem to be doing anything to affect the radio.What Im saying is
> by turning the shaft, it does not change the cutoff for the vfo. No
> change in the radio. Maybe this should be replaced despite the fact
> that I can see it working on the scope? I was having considerable
> difficulty getting the radio to reproduce the problem on the
> workbench. It would work just fine and when I put it back on the shack
> table it would act up right away. Now, of course, everyone is going to
> say, "something is different in the shack". My same thought, so I
> reproduced the same setup in the shack as I did on the workbench.
> Problem cropped up right away on the shack table. Took it back down to
> the workbench, problem wouldnt occur. Although I could get it to
> happen eventually. I even went so far as checking the voltage on my
> wall outlets to see if they were different and swapped the plug strips
> to make sure I was reproducing everything exactly. I was using a dummy
> load and took all antenna relays etc off line and bypassed. So, more
> troubleshooting today. This doesnt look to be an easy find.
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