Transistor switches

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MrDEB

Well-Known Member
Am building a circuit that has a 4030 low output to control a relay.
Had it working on breadboard but now transistor won't switch on (PNP)
I have no resistorson base, 12v connected to emitter
planning a revamp using just relay but need to turn on a 24v dc solenoid with a FET transistor??
circuit has 3 yellow lights that I will tie in diodes to the ground return to OR the 3 lights, then connect to relay.
Relay controls a red light that comes on if a yellow light is still on.
this is a starting tree.
any ideas on why the transistors quit working.
On low from the 4030 I read 2.8v on high it reads 11.8v.
 
With +12V on the emitter of a PNP transistor, its base voltage should not go lower than about +11V. yours goes down to only +2.8V so the base-emitter junction is broken.

The CD4030 can produce an output current of only about 20mA with a 12V supply. Enough current to kill the CD4030, not the transistor.
 
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