Ted, I tried to reach you of list but your email is no good. I have a 142
XL here I can meter out any segment you want me to. Write back direct.

Ronny K4RJJ


"Ted Busky" wrote in message
om...
My nephew bought a BC142XLT at a tag sale to try out scanning. It
worked for a less than 15 minutes, but then the display went dead and
there is just barely a hiss from the speaker no matter where the
squelch is set. He brought it to me to try to fix it. I'd like to show
him that you can still work on your electronics since this is all
through hole construction.

My first question is there a schematic out there I can get for free?

My next question is does the following troubleshooting information
make any sense to anyone?

I have opened up the unit and probed around a bit. The 8V regulator is
putting out 7.95V which looks good. The electrolytics don't look
tired. It looks like the receive section works because I get what
sounds like receive audio hiss from the audio noise output pin of the
MC3359 FM demodulator chip. It also looks like the audio secion works
because when I put my fingers on the input lines and around the
circuit I get some feedback and noise from the speaker.

I assume the UC1116 is some kind of controller. It looks pretty dead.
I probed the keyboard inputs and the ones that are not ground stay at
3.5V. There is no pulsing as I would expect if the controller was
scanning the keyboard. The diplay lines are mostly at 6.5V levels with
no pulsing I would expect if the display was being scanned. Not a
single segment comes on. There is a 390 ohm resistor that looks like
it got hot. This drops the input power to about 5.2V. This voltage is
present as long as the power is plugged in even if the switch is off.
There is a sine wave of 383khz at UC1116 pin 16.

There is an interesting circuit that is generating 20V and apparently
driven by an LM386 audio amplifier through a multiplier. I thought
this might be for the display, but the signal runs to a Harris chip on
the RF side of the board.

Any help would be greatly appreciated.

Thanks,
Ted