I just first say I'm a beginner and (keen but not experienced) amateur at electronics.
I have a 35 year-old Epson MX-80 dot matrix printer that I'm trying to bring back to life. A while back it started issuing thick smoke plus a bit of crackling. I powered it down straight away. My suspicion was dried-out caps even though the main caps on the power supply looked fine. To be on the safe side I chose to replace them anyway. But having taken the old caps off the board and tested them, they are responding perfectly well – my DMM says they're holding the rated capacitance.
Also, the smoke residue on the underside of the Epson's upper case somewhat suggests the smoke may have come from the transformer. I've stared and stared at the damn thing but can't see any obvious issue.
So my inclination is to do the following:
I have a 35 year-old Epson MX-80 dot matrix printer that I'm trying to bring back to life. A while back it started issuing thick smoke plus a bit of crackling. I powered it down straight away. My suspicion was dried-out caps even though the main caps on the power supply looked fine. To be on the safe side I chose to replace them anyway. But having taken the old caps off the board and tested them, they are responding perfectly well – my DMM says they're holding the rated capacitance.
Also, the smoke residue on the underside of the Epson's upper case somewhat suggests the smoke may have come from the transformer. I've stared and stared at the damn thing but can't see any obvious issue.
So my inclination is to do the following:
- Without putting the main circuit board back in, apply power to the printer and see if the transformer starts smoking.
- If it doesn't, start probing the cables coming from the transformer to see what voltages they're providing.