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  • Shop tales

    Speaking elsewhere about light sensitive parts reminded me.

    I used to work in the coin-operated amusements industry. Pinballs, video, jukebox, and in our case even coin laundry equipment. I was responsible for the training and oversight of technician crews. PArt of that involved writing and performing lecture/demonstrations about the service of the equipment. One piece we used in both arcades and laundromats was a dollar bill changer. And in fact my very first lecture was the ARDAC dollar changer. I prepared service documentation, demonstrated disassembly, showed how each subassembly worked, and how to troubleshoot. I really knew that unit inside out. Or so I thought...

    The ARDAC dollar bill validator - the thing that decides if the bill is real or not - was the kind where you placed the bill on a flat tray and bushed in into the machine. COntrast the modern kind where you end-feed a bill into a slot and a motor pulls it in. It tested IR transmission through the paper, it tested reflectivity, and it also checked the engraving line spacing in certain areas. It tested that you had an entire bill, not just a couple corners. Not that easy to fool.

    These tests all occur as you slide in the tray. If it likes the bill, it latches the tray shut, brings up rubber rollers to transport the bill into the magazine, and once it sees the bill has left the tray, THEN triggers a relay to send a vend pulse out to the rest of the unit.

    I had, still have, a power supply so I can run just the validator on my bench. A lamp indicated the vend pulse, if given. Plug the molex into the validator, and I did repairs and calibrations. I removed the rear cover panel to access the sensitivity adjustments and test points. Generally I put a dollar in the tray facing away from me. Squeeze in the tray, and if it accepts the bill, it cranks the bill out at me.

    I had one I had serviced, and was working. SO I flipped it on its face to install the read cover, and the vend relay trips. WTF? I set it back up and test it, all OK, solid as Sears. (As solid as SEARS WAS) Back on its face, and VEND> QUickly determined that putting it on its face triggered a vend. I pulled the front covers off, looking for possible circuit board contact with the front plate. I looked for wires that shifted. Something about being on its face.

    Bottom line was my unit was working fine, but on the little amplifier board was an optocoupler. And whenever I flipped the unit on its face, the little opto was right under my bright bench light. That light shone into it and triggered the relay circuit. If I had put the rear cover on the thing, the symptom would have disappeared. And did.

    But I wasted a couple hours chasing that problem.
    Education is what you're left with after you have forgotten what you have learned.

  • #2
    Back when there were VCR's and VCR repairs, I'd run into a similar thing. They use an infrared LED and sensors to sense if a tape is in the machine or not. The loading mechanism responds accordingly. Every once in a while, I'd get my bench light too close and encounter loading/unloading problems. Even when you know how it works, you sometimes forget.

    That could also come in handy. You could put a piece of electrical tape over the LED and trick the machine into thinking there was a tape loaded.
    "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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    • #3
      Originally posted by The Dude View Post
      Back when there were VCR's and VCR repairs, I'd run into a similar thing. They use an infrared LED and sensors to sense if a tape is in the machine or not. The loading mechanism responds accordingly. Every once in a while, I'd get my bench light too close and encounter loading/unloading problems. Even when you know how it works, you sometimes forget.

      That could also come in handy. You could put a piece of electrical tape over the LED and trick the machine into thinking there was a tape loaded.
      I had/still have, a dummy tape cartridge for VCR's.

      Wanna buy it...
      If it ain't broke I'll fix it until it is...
      I have just enough knowledge to be dangerous...

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      • #4
        I still have one, too............ somewhere.
        "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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        • #5
          I just went looking for mine... couldn't find it. Maybe I threw it out...

          I did find the book, Repairing and Maintaining VCR's.
          If it ain't broke I'll fix it until it is...
          I have just enough knowledge to be dangerous...

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          • #6
            Was it right next to the book, "How To Make Fire"?
            "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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            • #7
              Originally posted by The Dude View Post
              Was it right next to the book, "How To Make Fire"?
              No... but it should be....

              I actually still have a VCR hooked up in my living room.... I can't think of why....

              ... except I still have VCR tapes...

              ....and it's a high end expensive machine... I paid a lot for it, back in the day...

              Pretty much amortized now...
              If it ain't broke I'll fix it until it is...
              I have just enough knowledge to be dangerous...

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              • #8
                I remember when buying my first VCR (beta) The salesman was sure I was making a mistake opting out of the service plan. "The heads have to be serviced every X number of hours. It'll be much cheaper on the plan"
                Vote like your future depends on it.

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                • #9
                  Don't forget, VCR came back as ADAT some years back.

                  I have those VCR fakes too. I even have a tension gauge somewhere. I have a tension gauge for cassette too.
                  Education is what you're left with after you have forgotten what you have learned.

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                  • #10
                    Originally posted by galaxiex View Post
                    I had/still have, a dummy tape cartridge for VCR's.
                    I just had to use mine a couple weeks ago. Good thing I did too. An irreplaceable family tape that was sent to my Dad. I wanted to make sure the VHS machine wouldn't eat it, so I thought I'd try the dummy tape first. Sure enough the idler tire was dried out and it would have eaten the tape. Still need to try the other VHS machine we have, as I have to order some rubber, might as well do them both.
                    Originally posted by Enzo
                    I have a sign in my shop that says, "Never think up reasons not to check something."


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                    • #11
                      I'd send you my idler tire kit, but we'd likely have to pay $50 to ship plus customs.
                      Education is what you're left with after you have forgotten what you have learned.

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                      • #12
                        Yep. And the day after you sent it, you'd end up needing one for something.
                        Originally posted by Enzo
                        I have a sign in my shop that says, "Never think up reasons not to check something."


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                        • #13
                          Unless I need one for a garden hose or something, my need for idler tires has passed.


                          Mainly when I root through my storage, I am looking for weird stiff to challenge my friends on the "parts game".

                          OK, what is this thing?
                          Education is what you're left with after you have forgotten what you have learned.

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