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Old 05-22-2019, 06:28 AM   #1
reddsta87
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Default vending control board

Morning guys. I'm trying to find information about this control board for a wall mounted vending machine by slim line designs. I've tried asking the manufacturer but they want 600$ for a new one. They called it the LF-80 control board. I see similar looking boards on ebay but none just alike. I need some guidance on schematics, 1 to 1 replacements, part numbers, references, or any other info on locating a solution for getting this machine up and running. Thanks
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Old 05-22-2019, 06:43 AM   #2
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Default Re: vending control board

so whats wrong with the machine?
got a few pics of the machine it runs?
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Old 05-22-2019, 08:09 AM   #3
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Default Re: vending control board

first off, i'd re-seat everything that is socketed. Why doesn't it run? Is there power going to the board, is there any voltage on these large caps?
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Old 05-22-2019, 08:59 AM   #4
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Default Re: vending control board

i know these systems, they have a lot of diagnostic messages and are pretty simple.

top connector is the display & key matrix,
bottom connector is row/column drive for the vend-motors.
small upper-left connector is AC power - the rest are all for coin and bill handling.
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Old 05-22-2019, 10:07 AM   #5
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Default Re: vending control board

Correct. I am getting around 12VAC from the transformers to the board but there is no display showing on the LCD at all. The large caps I recently replaced, but i think there is one smaller cap directly beside the AC input that I removed but have not replaced tho I do have it ready to install. There isn't anything on the board showing that caps positive polarity side like there usually is and I'm not sure at the moment if it is directly connected to the neutral or if there is a diode in the path or not. The fuse from the transformer was blown when I received it so there might have been a surge that fried something before the fuse blew. Do you know any voltages/signals I should be seeing when its hooked up that would help have a better understanding of what the signal should be doing as opposed to what it is? I'll get a picture of the whole unit when i get home but its just a generic looking vending machine.
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Old 05-22-2019, 01:51 PM   #6
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Default Re: vending control board

Quote:
Originally Posted by reddsta87 View Post
Correct. I am getting around 12VAC from the transformers to the board but there is no display showing on the LCD at all.
If you know you have a transformer (i.e., AC) sourcing power to the board, you should be able to trace (visually) the flow through the input rectifier, bulk filter and regulator to see if you've even got "DC" supplied to the parts internal to the board.

If the fuse blew, it's likely something early in the power conditioning had a failure so the results should be pretty obvious (with a multimeter/'scope)

How far any such failure may have propagated into the board will depend on the nature of that failure...
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Old 05-22-2019, 05:05 PM   #7
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Default Re: vending control board

Something I would recommend would be to take a multimeter and see if the ground/positive are shorted. (You could probably check on either side of those big tank capacitors.) If it is shorted then that could mean that there is something like a shorted mosfet/transistor. (Or other sillicon part.) Fuses often blow because something "down stream" has gone short. I would probably also see if that Fet is shorted as a "first things to check" sort of process.
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Old 05-22-2019, 05:34 PM   #8
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Default Re: vending control board

Please also provide good clear hi-res of the whole bottom side of the board and also the pictures of the transformer connected to the board.
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Old 05-22-2019, 06:10 PM   #9
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Default Re: vending control board

pick a chip with known pinouts, like the 8pin 93c66 eeprom, and meter the power pins to check for 5v
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Old 05-24-2019, 02:06 PM   #10
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Default Re: vending control board

Did any of this Help? Sorry, I'm just curious how it's going!
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