I’m having problems repairing a 320vdc power supply that drives a stepper motor.
The circuit I’m working on uses a IR2110 Hi driver that drives a power mosfet.
When I connect my scope to the gate and the drain of the mosfet I get parasitic noise
and ringing. When I worked on the circuit the IC wasn’t using any sockets. So my question is it okay to use a IC socket to trouble shoot the problem? Is that the reason
I’m having trouble with noise? I’m using a high quality machined socket and it makes it a lot easier to troubleshoot the board.
Thanks in advance.
jmelect
Even a high-quality socket can introduce additional inductance and capacitance into the circuit, which can cause unwanted noise and ringing. you can try using shorter wires to connect the scope to the socket, as longer wires can act as antennas and pick up more noise.
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In addition to the inductance and capacitance changes already mentioned by @bidrohini, the resistance goes up with a socket. However for machined DIP sockets these changes are minuscule and rarely cause problems for circuits.
The minuscule parameter changes make measuring them extremely difficult so the gold standard debugging method is substitution (A/B testing).
Assuming you have a single assembly, you simply test it with and without a socket. If the problem never happens without the socket then you know the socket is the problem. Remember to replicate the test a few times to make sure you aren’t seeing a different and intermittent problem.
If you have multiple copies of the PCB assembly to use for testing, then you can create a more formal testing regime with control and subject groups saving some testing labor and increasing confidence in the results.
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