> Is there something that I'm not understanding 
> that would  
> cause the additional current through the beefier solenoid to 
> hold the  
> transistor open where the smaller solenoid doesn't?  When using the  
> TIP120s in parallel or the NEC, they don't fry and work fine after I  
> unplug power to the solenoid.  I'm confused...

To check whether that something is in the transistor(s) or elsewehere,
did you try to remove only the base current to get them out of the open
state?

Maybe you should consider using a mosfet instead of the biplar.

I assume you do have a good bleeder diode and/or snubber over the
solenoid?

Wouter van Ooijen

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