Panasonic AG DV1000 mini DV cassette recorder.
Complaint: Smoke came from the back of the recorder and then it failed to work.
Troubleshooting: I performed a very close examination of the top circuit board. I expected to find some burned component. The top inside of the unit looked pristine. After obtaining the service manual, I started checking the power supply as the unit showed no life, no front panel display was lit.
The AC power comes into a line filtering network and then goes into a full bridge rectifier, D1140. I tried to measure the output of that rectifier and found only 10 volts. I measured 16 volts going into the rectifier. This was nuts. The schematic showed absolutely nothing that would drop the line voltage down to that low a voltage.
I disassembled the unit so I could look the whole bottom of the circuit board over. The board was obviously waved soldered but the AC power connector showed a definite solder failure. The component lead could be moved side to side. The darkened solder showed the probable cause of the reported smoke.
Repair: I noticed that the power input connector leads did not readily accept solder. I should have removed the connector and tinned the leads before resoldering the component to the board.
After this repair, the unit worked fine.
Please take special care to get the small door, that opens for the tape insertion, properly in place for correct operation. I had to hold the door in an open position and then push the front plate on to the unit before the door would open and close properly.