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Royal Vendors Model 376-7 Coke Machine Displays Sold Out for all 7 selections

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Hello hive mind!

I have an older 90's Royal Vendors 376 model soda machine outside my home for the neighborhood kids. Recently it started displaying sold out for all selections and here's what I've done to troubleshoot but i'm now stuck. 
It's using a Marlin 3 - 4 button control board, and i've read through the manual twice. 

I've done the following
- replaced 24v transformer that powers the control board
- replaced the 4amp fast blow fuse that provides power to the control board/can release motors
- Put the unit in test mode, and confirmed I can press each button and dispense a can. All work as expected in test mode.
- Bypass the door switch which is supposed to reset the control board of sold out columns.
- verified every slot was half way full or more. Nothing is currently empty or has been for some time. 
- unplugged the coin/bill acceptor to see if maybe they were shorting something out (they were not). Behaves the same with or without them plugged in. (I've even tried a second coin mech just for kicks)
- visually checked all wires, looking for any loose grounds or cuts in harness's. Not seen any. 
- Powered off the machine, back on. With the door open or shut goes straight to sold out, whiteout having to push a button, which is why I don't think it's a paddle stuck, etc.

The machine has been in it's current location for a couple years now with zero issues. I will say before this happened, the machine would start randomly dropping out a can or two. I would walk by and find a can dispensed. When I reviewed the security camera, a can just fell out of the machine with no one around. This happened twice before the machine went into the solid sold out mode. 

I'm fully able to enter the programing mode by pressing the mode button on the controller board, and navigate around. However when I go into the price section to change prices, it goes straight into sold out and kicks me out of programing. I've changed prices in the past and never have had this happen.

I'm hoping it's not a fried board, and if so I've looked all over ebay/innerwebs and have not found any for sale. The only picture of my board I could find was here.

Apricate everyone's help. I'm getting tired of going out and manually opening the machine for the kids every day. They really enjoy putting quarters/bills in. lol

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Oh come on, put a proper door switch on it.  That is the problem here.  The machine isn't recognizing the difference between the door open and the door closed.  Having said that, you could have a power problem like surges or brownouts, florescent bulb interference, or just a faulty board.  You need a Merlin 1 or maybe 2 board.  The RV376 was from the first generation of Royal. Here is your manual:

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Thanks for that info. I should say I do have a new door switch on the way, I simply tried by passing it to see if that was the problem, as I had read on other forms, that was a way to test for a faulty switch. I'll update once I have the new switch here in a few days. 

I do have the florescent bulb's removed. Those have been out for a couple years, however I have not disconnected any of the power sources. Not sure if that matters or not. 

Humm, sounds like someone in the past has replaced the Merlin 1/2 board with a 3. I'll do more research around that. Thanks for the pdf!

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Got the new door switch today, and the machine still behaves the exact same way. As soon as I close the door, the LED displays Sold Out without pressing any buttons. Guessing it's time for a new control board. 

Does anyone know if I can simply find an old merlin 2 board for a 376 and throw in there? Having a marlin 3 board in there now wasn't sure if I would have to re-wire/do anything special to down grade. (Assuming Marlin 3 is newer than 2). 

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It's Merlin, not Marlin.  It ain't no fish.  A Merlin 2 board is what it came with so yes, it will work.  Before you do that try wiring the switch the other way - it might be backwards.  Oh, and you might have not known or tried this, but you do have to hold the door switch in when testing the machine.  That requires a foot on the switch, a finger on the door buttons and a hand on the delivery chute to catch the can. 

Edited by AZVendor
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I had a problematic royal can at one time.  Everything got replaced, did t solve it.  We concluded it was irregular voltages due to an overloaded circuit.  Location wouldn't give usa dedicate circuit so we pulled the machines and scrapped them.  Never resolved tbh

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  • 2 weeks later...

Update on my resolution. 
Called every business that resells parts I could find. No one had the Merlin 3 board I was looking for. Called Royal and they said they had one more left in stock, and there would be no more made after it's gone. They wanted $550 for the board, and I decided it just wasn't worth it. 

Looked around on market place and found a Royal 650 which had quite a few broken parts/issues going on. 

Brought the 650 home for $350, and swapped out the cooling deck, LED Display from my old 376, fixed some broken motors and I now have a fully functional 650 Live display machine in it's place all for the same $ I would have spent on the older 376 board. 

In the end it was a happy ending with allot of elbow geese. I was surprised how many of the parts were interchangeable between the Royal 376 & 650. Basically everything accept for the vend motors and control board/random buttons.

Thanks everyone for your help!

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You now have a much better and reliable machine than the 376 would ever be.  And more flexible for products.  Royal was very good, in the beginning, of carrying many common parts forward through their models.  Interesting note: Royal was started by some engineers from Dixie Narco so when the first single price Royals came out to Pepsi, some of the parts on the Royals looked awfully familiar to what we saw on Dixie Narcos.

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