The Topward 1302 multimeter performs as expected.
I left it plugged to AC outlet in OFF position for a few days after the last use. Then I had to move it away from the bench and I got a hot surprise: the transformer was hot enough I could not hold the finger on it.
WHAT? It was plugged but supposedly turned off, the display unlit too. Even if the ON/OFF switch would operate on the low-voltage circuits, why would an unloaded transformer get so hot?
Time to have a look at the actual circuit.
Good news. The PCB reports the product name as "TDM-104", which brings up a PDF manual from the Topward website. The schematic diagram confirms the transformer is always connected. Therefore also the diode bridge and capacitors are active when the AC cord is plugged in.
I probed voltages and they all seem fine. There is no ripple detectable with the multimeter.
Considering this product probably sat in the low-end side of the market, it was cheaper and safer to power off only the logic circuitry rather than the whole AC. Who cared about saving power in the 1980's?
