I'm working with some DCSSRs wjohn gave me with 24VDC. The 3rd channel of 4 automatically turns on after powering the SSR for a small period of time. It "ramps up".
I thought -- humm bad FQPF13N06L (MOSFET), but I replaced it and to my amazement the issue persists.
- I've checked the resistance on the base for the MOSFET on all channels and they are to spec.
- I've removed the opto and the issue exists -- this eliminates the 7805 and all but the MOSFET, 24VDC, and 1 resistor from the troubleshooting based on the schematic.
- Again, I replaced the MOSFET (FQPF13N06L) and it persists.
- I swapped out the light I was testing it with for another thinking it was shorted or something, and the same issue persists.
- I disconnected the 3rd channel outputs expecting a different channel to drift on and the other 3 worked perfectly.
- When I use my mulitmeter on the MOSFET base then + and - it turns on and off, but still drifts back on later.
- All other channels work PROPERLY.
Only mod to the DCSSR is the 7805 is a SMT style, that I fit to the back of the board, but when I pulled the opto this part of the circuit should be inactive, so I do not think it is that.
Cannot send pics until I go home.
Very confused and in need of some ideas -- Jboyles.