I have this circuit


I am suspecting the Q3 or K1 is bad.
When I apply 15V to K1.
I am seeing +15V at 4 and +15V at 8. It should be LOW on 8.
How do I go about checking to see if this K1 is faulty?
thanks

 

It should be LOW on 8.

If the line driving pin 8 is open circuit then a DMM connected between pin8 and ground will read +15V, because the meter resistance is much greater than the K1 coil resistance.

 

What's at the top of the circuit? The connections to pins 4&8 go offpage, so we don't know what is controlling your relay.
On the same vein, what is R2R5-E9? The relay connects to a signal there as well.

Basically, you have asked what is wrong and unintentislly (or intentionally) omitted everything we need to know.

 

I have this circuit

I am suspecting the Q3 or K1 is bad.
When I apply 15V to K1.
I am seeing +15V at 4 and +15V at 8. It should be LOW on 8.
How do I go about checking to see if this K1 is faulty?
thanks

Hi

Check if there is a suppression diode across the coil of K1. It might be shorted.

eT

 

Is the relay socketed for easy removal? (easy to test by itself out of the circuit)
Or soldered to a PCB? (not so easy to desolder to test)

But yes.. without the rest of the schematic we don't know if what you are seeing is correct or not..

 

If you have 15 volts going in and 15 volts coming out, ground is missing?
Like others have said, where do 4 and 8 come from or go to?

 

yeah. ground is missing.
we realized that the founding pin is not is place.
we got that fix.
thanks.