Ian,
I am going to assume that this SSB adapter was working fine before the
failure, and I'm also going to assume that it attenuates signals when either
the OP1 filter or the CW filter is selected. If either of these assumptions
is not correct, I may be way off base.
First thing to check is RFC1 and RFC2 - check them for continuity and also
for a possible short to a crystal case. Slide a piece of paper between the
crystal and the choke as a quick check.
You say you have checked the diodes already, so for now figure that they are
OK.
Check R5 to be sure it is well soldered, and check the soldering of the
diodes and R-paks near the filter. A bad solder joint can sit there and
work fine for a time, but eventually fail.
Check the operation of the switching control voltages. RXS (U1 pin 21)
should be active (about 5 volts) when the OP1 filter is selected, and RXC
(U1 pin 22) should be active. These signals should be mutually exclusive,
and during receive you should have one or the other active, but never both
of them active or inactive at the same time.
If those steps don't correct it, it is at least a good start. Get back to
us with the results.
73,
Don W3FPR
> -----Original Message-----
> I am hoping someone can point me in the right direction here.
> My SSB board seems to have developed a problem. TX is fine but RX is
> really down. Even stations who would normally peg the S Meter barely
> register. If I remove the board and jumper the 2 connectors, the
> receiver springs into life. I have checked continuity on the torroids
> and checked the pin diodes (in circuit with the diode position on my
> DMM) and all seems to be well. Voltages on U1 appear to be ok but I am
> getting a small reading on some of the pins that should read zero (in
> the order of 150mV)
> Any ideas chaps?
>
> Ian
>
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