12-29-2016, 08:04 PM
At the workbench.
Mondial, the first thing I noticed when I began to look this area over tonight is that it is apparent that TR701 and TR702 have been replaced previously - and whoever did it did a very sloppy job.
While I did not see any solder bridges, it is a wonder that there aren't any. There are large solder blobs on topside of the PC board, on the leads of TR701. And the "serviceman" used too much solder to solder TR701 and TR702 into place.
My readings:
TR701, schematic readings followed by my actual readings.
C - 1.6 / 0.5
B - Not given / 0.495
E - 0.02 / 8.8mV
TR702, schematic readings followed by my actual readings.
C - 9 / 15.3
B - 1.6 / 0.5
E - 0.77 / 60.2mV
Voltage at the cathode of D702 does not change when the knob (actually, the knob shaft as the knob is not currently on the shaft) is touched. The wire from the tuning knob shaft is in place and has continuity from the knob shaft to point 15 on the tuner PC board.
It looks like a rebuild of this circuit is in order.
Since I am faced with that chore, and since my LEDs for the pointer have yet to arrive, I think I am going to set this unit aside for a little while. I'm not giving up on it, though - I am hoping that I can restore this circuit to proper operation. I'm looking forward to this unit having a properly working Auto Magic circuit.
Mondial, the first thing I noticed when I began to look this area over tonight is that it is apparent that TR701 and TR702 have been replaced previously - and whoever did it did a very sloppy job.
While I did not see any solder bridges, it is a wonder that there aren't any. There are large solder blobs on topside of the PC board, on the leads of TR701. And the "serviceman" used too much solder to solder TR701 and TR702 into place.
My readings:
TR701, schematic readings followed by my actual readings.
C - 1.6 / 0.5
B - Not given / 0.495
E - 0.02 / 8.8mV
TR702, schematic readings followed by my actual readings.
C - 9 / 15.3
B - 1.6 / 0.5
E - 0.77 / 60.2mV
Voltage at the cathode of D702 does not change when the knob (actually, the knob shaft as the knob is not currently on the shaft) is touched. The wire from the tuning knob shaft is in place and has continuity from the knob shaft to point 15 on the tuner PC board.
It looks like a rebuild of this circuit is in order.
Since I am faced with that chore, and since my LEDs for the pointer have yet to arrive, I think I am going to set this unit aside for a little while. I'm not giving up on it, though - I am hoping that I can restore this circuit to proper operation. I'm looking forward to this unit having a properly working Auto Magic circuit.
--
Ron Ramirez
Ferdinand IN
