PE+ coin-in optics problem

[knagl]

After moving a few months ago, I finally got around to firing up one of my PE+ bartop machines.  It came right up and I dropped a quarter in the slot and, to my surprise, the machine accepted the coin but did not register a credit (nor a coin-in tilt).  I tried another coin, same deal.

The comparator is accepting coins correctly and they're dropping into the hopper correctly -- I discovered through some troubleshooting that my problem is the optics -- specifically the "A" coin-in optic.

No matter what I do, the "A" optic always shows a reading of "1".  (In the idle state, all three optics show "1" -- when a coin (or my test piece of cardboard) passes through, optics "B" and "C" change to 0 momentarily, but the "A" optic doesn't change its state -- it's always showing 1, even when the optic is blocked.

I partially disassembled the coin-in optics and used a digital camera, and can confirm that all three emitters are working.  Further, if I had the optics close enough I would get "1" readings for B and C which would change to 0 when I covered the receivers with my finger (or moved the board away) -- the "A" optic always showed a reading of "1" no matter what.

I swapped coin-in assemblies with my other PE+, and the other coin-in assembly works correctly in the same machine, so I've isolated the issue to the coin-in assembly -- the problem is either with the optics board (likely), or the wiring on the problem coin-in assembly.

Short of, "replace the optics boards", any ideas?  The machine was working correctly prior to the move.  Thanks!

[jay]

Other than a blown or shorted receiver on your A optic I can't think of anything else that would cause it to always register that it is receiving a constant beam of light.
You have eliminated harness issues by swaping out the optic board, and of course by reinstalling it you have reseated it etc.

[knagl]

Other than a blown or shorted receiver on your A optic I can't think of anything else that would cause it to always register that it is receiving a constant beam of light.
You have eliminated harness issues by swaping out the optic board, and of course by reinstalling it you have reseated it etc.

I haven't quite swapped out just the optic assembly -- I guess that would be the next step, put the problem optics in the working coin-in assembly.  My hunch is that the receiver went kaput, but that doesn't strike me as being a common problem.

Thanks for the feedback!

[stayouttadabunker]

It sounds like the receiver diode or triac is "stuck" closed - forever sending the MPU a "1" signal.
I don't know which diode/triac component controls that signal...
I think it's "Q2" but I'll leave it up to Jim or Channelmaniac to decide which one.
There's some articles in which a certain diode component at certain locations
(depending on the board version)
which can be snipped off to bypass the stuck signal.
The component is so tiny to solder that it's very very difficult to replace
unless you have the right soldering equipment.

[Jim]

The "A" optic is usually the one affected  when the transistor Q-2 or Q-4 shorts placing a ground on that detector. Removing this transistor will cure the problem.  Removing that transistor will not affect the operation of the optics .  I would try this ,its an easy fix.

Jim

[knagl]

Jim- Thank you for the idea.  In my situation, the "A" optic is always reporting that there is nothing blocking its path, even when there is.  If I'm reading your post correctly, that's the opposite of what you described, right?

[Jim]

The transistor shorting affects the detector, it keeps it in the "1" state regardless of what happens to the beam from the emitter. normally, the beam will hit the base of the detector and it will conduct and put a ground on the pull up resistor pack causing it to change from a high to a low, in turn the result is a "1" displayed in the test 10-1, when you break the beam (coin passing thru) the ground is removed from the resistor pack causing it to go back to the high state and displaying a 10-0, when the transistor shorts it places a ground on the collector  and holds that resistor pull up to a permanent low, giving you the constant 10-1 . that's why it never changes, regardless of what you do to the beam.

I'll edit my other post, with a ground on the detector it believes there is nothing blocking the beam.    you were right    

I think I'll have a beam and coke after all this        try removing the transistor, either way, I'll send you one that works. 

Jim

[knagl]

I'll give it a shot as soon as I'm able to get back to working on that machine, and will post my results.  Thanks for the suggestion!

[StatFreak]

Jim, given that the circuit still works if the transistor is removed, why did they put it there to begin with?
What does it do?

[Jim]

I was told it was some interaction between the optics and the coin comparator so the game would not function with out the coin comparator present.


Jim

[StatFreak]

I was told it was some interaction between the optics and the coin comparator so the game would not function with out the coin comparator present.


Jim

Thanks.