Howdy fellow repeater builders.
My Micor UHF ham band repeater has gone deaf.
Basic troubleshooting reveals no discriminator output
When I hang a scope on the input to the 2nd IF amplifier everything
looks great. I can key up my FT-817 on the machine's input frequency
and see a nice signal with deviation as I talk. Switching to another
repeater frequency on the FT-817 I get nothing so I'm sure the
Channel element, mixer all the doubler circuits and all the other IF
stages and crystal filter stages are ok. The output of U102 the 2nd
IF Amplifer M6707 IC has nothing. I pulled one end of C192 the end
that goes to L137 from the output of the AMP. This is easy because
it's mounted dead bug on the back of the PCB. Still no output from
the AMP. I did this to make sure no other circuitry down the line
was holding down the output of the AMP. So I think the four diodes
in the discriminator are OK. When the machine is cold and been
powered down for 30 minutes or so the amp seems to work for about 5-
8 seconds when first powered up then shuts down so I'm pretty sure
this IC is bad.
The questions are:
A. Is this a common problem?
B. Where can I find a replacement?
C. Is there a new device that can be used in it's place? It's in a 9
pin round package.
D. Shoud I look for an old mobile UHF Micor and remove the part?
Thank You group and have a nice Labor Day weekend.
Bill N5ZTW
