On Sun, 18 Dec 2011 09:23:09 +0000, frank wrote:

Hi Ken,

Ken Fowler wrote:

Hi Frank,

The reason that it suggests to inject the 467 KHz IF signal into the
mixer grid is that the tube will serve as a capacitive coupling for the
signal into the IF amplifier. If you try to inject at the mixer plate,
you have to worry about the high voltage at that point. If you can
hear an output with the signal injected into the mixer grid, the IF
amplifier is working. Then you can inject the 4.6 MHz signal to see if
the mixer is working. If the second mixer is working, move back to the
grid of the first mixer with the 4.6 MHz signal. Etc. Etc. Of course,
it would help to know what level of signal at these points should cause
a normal output. Good Luck and watch out for those plate voltages. In
fact, it is not a bad idea to check the DC voltage on the control
grids. If the voltage is positive, it might mean a leaky coupling
capactior.

thanks for all suggestions, I'll check the voltages on the grids first
of all, even if capacitors should be ok, all tests I made showed no
leaks on them, but I didn't test *all* of them as some are difficult to
reach. I haven't been able to find either a DC voltage chart or an RMS
signal chart for this receiver, so I guess it won't be an easy
troubleshooting.

Count on just about every stage amplifying, at least a bit. If you
inject a signal at the correct frequency someplace, it should come out
down stream, only bigger (assuming it's not so big that AGC is knocking
it down).

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com