HOW to tell the capacity (& V.max) of the SMD capacitors

[ci139]

it's the reusability of blown UPS spare's

& the precautions to unsolder/re-solder SMD FET-s (such as prefferred order 4 S,D,G)

 

[ronsimpson]

I reuse SMD components (some).

If you did not order the parts from a supplier then you do not know their maximum voltage.
Some parts have no markings.
Some parts will have a YA5 that might work if you know who made the part. That code could be on a IC-opamp, IC-buffer, transistor or a capacitor. You have to use your head and have some luck.
Resistors might have no markings. or 103=10k? A=? 1013= maybe 101k 1% wattage is a big?

 

[Sceadwian]

You could test a couple of dozen capacitors of a known value and increase the voltage until greater leakage current is noted, this will increase as you surpass it's voltage limit, compare this to similar leakage currents on the known diodes at the same voltages and you should be able to approximate the value, but it be pretty painstaking.

 

[ronsimpson]

You could test a couple of dozen capacitors of a known value and increase the voltage until greater leakage current is noted, this will increase as you surpass it's voltage limit, compare this to similar leakage currents on the known diodes at the same voltages and you should be able to approximate the value, but it be pretty painstaking.

When measuring for leakage current; the current will go from uA to Amps very fast. Use a resistor for current limit. Size the resistor so only 10 to 100uA will flow when the part under test is shorted.