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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.
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.
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