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I just bought a Dixie-Narco DNCB 501T/MPC-8 for $150. The previous owner said the machine just stopped charging people for the soda, and dispensed them for free.

But the first issue I’m having is that I can’t seem to go through the menu how I’d like, and it seems to do what it wants.

After plugging he machine in the display screen started going up in .50 increments non stop up to $99 and then seems to go trough all the menu options for a bit before doing it all over again.

I followed the instructions from another member of the forum who replied to a comment asking about how to operate and set the prices of this machine. (Link) https://des.az.gov/sites/default/files/media/dn_501_e_and_t_operators_manual.pdf

After pressing 1&2 at the same time to try to get the menu to appear, the display seems to react as it stops going through menu options or increasing the price by .50 so fast but that’s all it does. It doesn’t seem to go through the menu when I hit the buttons but just slow or pause it for a couple seconds. But it did change the price a little as the display was increasing from $1 to $1.50 to $2 etc. But after messing with the buttons it’s now jumping from $1.14 to $1.64 to $2.14 etc. But I can’t seem to get the machine to react like this and change the prices again, unintentionally or not lol.


Any ideas? Thanks in advance!



Edited by Default32

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You either have bad selection switches on 1 and 2 or, more likely, a bad MPC logic board since it's now doing it in .04 increments which should never happen.  To address what happened before you got it, there could be one or more bad motor switches on it.  One thing to check for is that there should be metal plates that separate the middle motors from each other.  This is to isolate stray electronic interference from motor to motor.  If those are missing this could all be the result of that.  I mention it because I know why the plates are there but I haven't worked on a machine that didn't have them.

Make sure it has a good, functioning door switch as well because the programming is dependent on that.  As I recall, the switch can keep the machine in the service mode after the door is closed in some cases and that means that when you press buttons on the selection panel after the door is closed you can affect the programming.  This was Dixie Narco's first mainstream logic board machine and it has issues and it is nothing like their later boards.  It has quirks and odd programming that can really trip up someone who doesn't read the programming directions and follow them in a precise way to go through the menus and change things.

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Firstly, thank you very much for your response I do greatly appreciate it!

But what do you mean by "Middle Motors"? Is that the Motor Switches? Where would these be located, not able to find where these would be with a simple search as I thought, but if I look in the machine later I may find them easily.

Also, with this logic board having enough issues in general, is it possible to do a complete conversion to MBD replacing the MPC altogether? I don't know too much about this cause like I said this is my first vending machine, but I have done some little reading on this and it seems as if it converts the machine to a completely different operating system I guess I would say. I would be willing to spend around $200-$300 to do this if this made the operation of this machine much more user friendly as well as gives me the option to add a card reader to this machine, I think it would be worth it in my eyes. As long as as I felt confident enough doing it myself as I'm a hands on person, or found someone in my area help me if it were maybe too technical or sensitive to error. 

Also, with the search that I have done so far, it seems tricky to be able to find a decent amount of parts for the 501T in comparison to the 501E or other models. Would you happen to know of a good place to find parts for this machine? Or if you know of a parts list that includes part numbers that I can use to find the proper parts for this machine instead of looking them up by the model of the machine which doesn't seem to produce too much.


Once again, thank you very much for taking your time to respond to me, I do appreciate it.

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I think he may be referring to the 4 motors in the middle columns(selections 5-8 are narrow columns but located in the middle of the cabinet).  The motors should be closer together than the outside wide columns.

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You can't do any card readers on that machine.  There is no aftermarket boards for it and yours can't do MDB.  There are tons of parts available for it as its no different than a single price machine save for motor switches, logic board, harnesses, etc and most of them would be used.

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A little update and more questions I guess.

OK, I finally found a couple sites (https://www.capitalvending.com or http://www.s-t-a.us/stavend/index.php) that repair boards/validators/coin changers etc. So I feel good knowing I found a couple places to get parts and things fixed, now it's about troubleshooting.

First off I realized that I don't know how to 100% get this machine set-up, to test all the functions of the bill/coin mechanisms. First off how to I home the motor/cups? I know I have to "prime" and partially fill the machine first or at least make sure it's not completely empty. Then I have to fill up the changer with nickels/dimes/quarters. Make sure my price is set to what I want hitting the service button after, and then closing and locking the door. Now the machine should be ready to vend for the price I set correct?

I'm assuming these metal plates between the motors are the ones behind the metal cover with the sign saying "Check Display for Flashing LED"? I will check the next time I look if so.


Also, I did figure out how to go through the menu options and change the price setting after hitting the service button, as before I was hitting the stupid door switch... (Dumb I know, like I said first machine lol)

I got a piece of paper that has some instructions, it says that I'm supposed to be able to change the price for each selector. But when I tried to change the prices on a different selector, it was at the same amount that I set on the first one, basically no matter which selector I change, it changes the prices for all of them. Is this actually only a single priced machine, doesn't this hold bottles as well on the 3 outside columns?

So selection switches 1 & 2 work do work, and I believe the door switch does as well, because the display screen goes blank and stays that way when I hold it, but when I release it, the count starts going up and goes through the menu options like before, which I don't believe it's suppose to do right?? Would this be further evidence of the MPC being bad, on top of it going up in .04 increments? But after unplugging and replugging the soda machine back in, it went away and went back to going up in .50 cent increments. I just want to be sure that this is the issue before I go spending $100+ replacing the board.

--- So back to the previous issues of dispensing drinks for free.

First off the bill validator is blinking twice. And on the validator, it says when the LED blinks twice it means it's "Disabled from mech/VMC". This is what the instructions I have refer to as well, and say that setting the prices will fix this issue, but it doesn't.  (Unless this was because the machine was completely empty at the time as well???) Bringing it up just in case...

I noticed that one of the plugs going into the bill validator was crooked, and wondered if this could cause an issue like this even with no wire in that specific slot/spot on the plug?


When I took it out I noticed that the plug itself had damage to the bottom of one of the 18 slots that fits a prong, and taking a photo of the prongs inside the validator I noticed that one of them is deformed/bent. 


Also, I noticed that on the Door Switch and selector #8 (I believe) next to the Pepsi button, that there is a Wire 'Crimp' Terminal, but no wire connected to it. Seemed odd especially on the selector as every selector besides this one had a wire in that spot.


Door Switch Wires


(No wires in middle two Wire 'Crimp' Terminals)

Once I get a little bit of time I will make sure that the machine is set-up, properly primed, and ready to vend to see how the machine reacts. Like I said the previous owner said it just stopped taking money and started vending for free. But I haven't even gotten to the point of testing this, as finding information or instructions about how to operate this model seems to be difficult to find, but I am finding some, slowly but surely.

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I doesn't sound like you bothered to search for an MPC manual.  Here is the main manual followed by a Technical Service bulletin that may be of use.  Follow the manual though.



Your coin mech might be a single price mech.  What model mech do you have based on the side lable of it?  If you are running a single price mech then you need to set your Escrow setting to Escrow to Price.  If you have a logic mech that allows the board to be set to multiple prices then you want to set Escrow to be Last Bill Escrow.  

Don't unplug any harnesses with power applied.  Yes, the bent pin in the validator connector is a problem.  Someone installed a connector incorrectly and bent it and it must be fixed.  On this machine, the validator will always be disabled when the door switch is in the middle (service mode) position.  The terminated wire on your selection panel is normal.  There is always one at the end of that circuit on single price machines which can be on switch one or eight depending on machine model.

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My gosh that second manual is very useful, thank you!!

I did find manuals as I have the first one’s link saved to my desktop, but being so new to this I was unsure which ones I could trust as I didn’t know how specific the manuals were and if I could use the ones I found, but I’m understanding that all I need to really look for is MPC.

First off, yes there are plates between the 5 motors in the middle.


Coin changer type (below)



Motors turn for all columns except motors 1 and 2 as they won’t rotate and start clicking repeatedly as if they’re jammed, although there is no noticeable jam. Motor 2 has a decent amount of grease/oil on it, motor 1 has some as well but less. Motor 3 doesn’t seem to have noticeable amounts of grease or nearly as much, wondering if they tried to lube the motor? Also,

Motor #2 (Selector 2)


Motor #1 (Selector 1)


vs motor 3 (selector 3) that doesn’t seem to have been greased recently. (below)



Testing the coin & bill mechanisms:

I filled each row in the coin changer with 12 nickels, dimes and quarters. But when I tested the coin dump function it only worked for Dimes (selector 2), and not Nickels (selector 1) or Quarters (selector 3).

When I go through HPc (historical product count) it shows the correct selector number that I’m pushing and then shows separate product counts for each column. So all selectors work fine.

When I took the bill validator out to fix the pins, I watched the door switch as I could see through the opening while opening and closing the outer door. And it seems as if the door switch only has two positions, when the door closes the switch gets pushed in a little (around 4-6mm) until you hear the click and the door is closed. And as you open the door a few millimeters you hear the click of the switch again. Pushing in the door switch by hand, it seems that there is no third position unless that position is obtained by pulling the switch out manually?


Photo below, switch pulled out manually.(lol, don’t judge if this is dumb 😂)


I can pull the door switch out by hand and the display goes blank for a couple seconds before it come back to the continuous counting. When I seen the display pause and go blank when I manually pulled the switch out, it made me think it was supposed to react in a certain way that it isn’t currently doing. When I push the door switch back to its resting position while open, the counting pauses for a couple seconds without the display going blank, and then continues.

After the machine is opened, the display continuously increases by the increment set on the S-P menu, only pausing for a moment when the door is closed/door switch pressed before continuing to increase. After having the machine plugged in for an extended period of time, the increments change by itself, increasing the increments by $.04 instead of $.05. The  amount on the display gets to $99.50 before it starts going through menu options and unreadable letters/numbers on the display.

With all this b.s. going on, I still wanted to test the coin and bill mechanisms after filling two columns with a 12-pack, the changer with 12 coins ea, and fixing the bill validator prong that was bent, allowing the plug to now fit properly, and yet it still didn’t work 😦😂 (I did test both Escrow settings of, Pr for the single price and E-51 for multi-priced)

But I’m wondering if you think the issue with motors 1 & 2 not turning, the coin changer not dumping nickels and quarters, could be a result of the MPC or Motor Switches going faulty? Would the motors still tick/turn if the motor switches were faulty? And if you think it sounds like door switch needs to be replaced?

Should I replace/repair the MPC first, then test the motors and coin changer again, before replacing the motor switches or repairing/replacing the changer and motors.

Just wanted to say thank you again for helping! I have learned so damn much about vending machines in the last few days and have been really enjoying it. I felt nervous and overwhelmed at first, but now I feel more confident as I’m much more comfortable with, and understand the machine a lot more. 


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Never-mind about the door switches, found the part where pull out = normal mode. lol

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Not understanding the three positions of the door switch tells me that you haven't actually read the manual yet.  The door switch is explained in the manual. You have a bad coin mech, a bad logic board, bad motors on columns 1 and 2 (you never need to oil a motor, that just masks a problem), and you should have the bill validator tested when you get the coin mech fixed.  Since the coin mech is a logic mech and not a single price mech you will make the escrow setting I mentioned before after you put the new logic board in.

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