Sigma PT 4B rejects all coins

[cbard]

I'm new to the slot machine world learning as I go. When I got this machine I was told the machine was working fine and then just stopped. I found that the power supply was not putting out the required 12v. So I added a second power supply for the 12 volts. The unit came to life.
Now the new problem, every coin goes right into return bin. The coin comparitor has a red light that is lit. I have changed the quarter and cleaned around it. If I  wedge the rake open that directs the coin and the coin goes down into the hopper the coin register as a credit. But if I drop more the 1 coin without hitting the play button I get an error message about no coin pluse .
Do I need to replace the comparitor or should I be looking some where else. I have attached a photo of the unit.
Thanks for any assistance

[Lcarter114]

Did you ever get your coin comparitor to work.  I have the same machine and it is very inconsistent in taking coins.

Thanks

[Chris-socal]

Are there any error codes on the LED readouts?
Does it make an error tone when the coin drops through?
Is PT-4B the machine that has three key switches on the right side near the top?
Are there 3 power supplies mounted on the inside ceiling of the machine?

[Lcarter114]

No error codes.  It has the 3 key switches.  I think the coin mechanism itself may have issues.