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Yamaha PX-3 photointerrupters and other issues causing problems

Tried several places, first the blue wire that goes to the motor board screw from the main board. Then, the blue wire that comes from the power transformer to the main board.....
 
I'm not sure what to say about all pins measuring 0 Ohms now?
You are sure the meter is on Ohms, not volts?
 
They are not measuring 0 Ohms, they are, for example, pin 1 is 2.275 kOhms
 
Pin 2 is 11.45 kOhms and each pin gives me some similar reading instead of 0L
 
That is OK and expected that you will measure a high resistance, which is MUCH different than 0 ohms. A reading of 0 Ohms probably means a short, but a reading of some other is either internal resistances or external paths between pins. So back to my original question... when you measure pin 14 to Gnd, do you measure a resistance or 0 Ohms?
 
Fishead said:
OK, so with the power off, I get continuity to ground, not only on pin 11 but on EVERY pin on IC 2.
Click to expand...
So what did you actually mean by this statement above, that you measured a resistance or "continuity" (meaning 0 Ohms) to ground?
 
Pin 14 measures 4.502 kOhms......not sure where you were asking for pin 14? I thought we were still on pin 11, sorry.

PS - Pin 11 measures 11.14 kOhms
 
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I was asking you to check to see if pin 11 (sorry typo on post #67) was shorted to ground by measuring the resistance from pin 11 to ground to see if it measured close to 0 Ohms. I asked to make sure that the signal trace from TR7 collector to IC2 pin 11 had a short to ground causing you to measure 0VDC instead of 11.6v. But it sounds like you do not have a short to ground since you measure a resistance. In that case, I would think that TR7 is bad.
 
Thank you for clarifying.....I kinda thought that was what happened which is why I included, later, the value for pin 11.

How to test TR7? How could that go bad when I did nothing remotely (to my knowledge, and that's questionable for sure!!!) close to it and sure didn't unsolder it or anything. Is there a way to test that component?
 
Does your DMM have a diode or transistor tester? If not we can test the resistance like diodes.
By the way, this might be an issue but might not solve other problems that you encountered, but needs to be corrected.
You will probably need to unsolder the transistor to test it.
 
My multi meter does have a diode tester, it's on the same setting as Ohms but you select a different parameter. Here's the MM that I have:

 
Thank you, I'm learning......

I tested the TR 7 and got:
Step 1 (B to E): OL
Step 2 (B to C): OL
Step 3 (E to B): 0.684V
Step 4 (C to B): 0.678V
Step 5 (C to E and then E to C, switching pos and neg): 0.848V and 2.724V

So, it all checks out except Step 5......however, this was a test without taking the TR off of the board.
 
Looks like I may need to unsolder TR 7 from the board to get trustworthy results......yes?
 
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