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national 432 turret problems


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New vending tech here - currently working on a 432 shoppertron with turret issue - can't seem to get this machine to rotate properly. This unit will not properly stop at all programmed locations without having to re-home itself - does not matter what position it is at, whether it be zone 1, zone 2, zone 3, etc..........So far I have adjusted the stop pin, changed stop pin optic, encoder optic and encoder disc, interface board, home switch, and long ribbon cable from controller to interface. Been through the programming, etc. with tech support, all appears to be ok there, replaced recommended parts, same problem......no errors in diagnostics......sometimes turret stops in proper position, then re-homes, sometimes it stops short in-between compartments and then re-homes itself. Can not step through 1 complete revolution before unit re-homes to zone one, but unit re-homes to proper zone 1 spot, and never displays "can't home" - does not matter if using internal switch, which only rotates in one direction, or external buttons either....no difference door open or door closed....re-homes in either direction.... about ready to pull this machine back to the shop.......figured I would try posting here first, as this is an excellent go-to site for many issues - fantastic forum you guys have here. Also, seems to be a bit of play in the turret when stop pin is engaged - perhaps a worn/loose stop pin bushing or motor drive coupling causing this thing to jump/lose count? Wasn't sure I could get the turret back in myself, so have not been able to check those yet.......Any ideas or suggestions would be welcome - thanks,

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Boy, this is a tough one since you've already replaced most of the parts AND gone through tech support.  Have you tried replacing the stop pin switch or the switch cam?  There also used to be an adjustment on the 431's where you put a nickle between the armature of the stop pin solenoid and the body of the solenoid, then adjusted the solenoid body up tight against the nickle for proper solenoid spacing.  Maybe this also works on the 432?  Maybe a new stop pin assy or a new logic board?  Do you actually have the machine programmed to run all three zones of the turret with none locked out?

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Thanks for the reply AZ,  the 432 doesn't use a stop switch like the 431, there is an optic which gets blocked by a lever attached to the stop pin - as far as programming, ram clear had no effect on problem, machine is set to shop all zones, levels are all 2 and 3, and prices on each level are uniform. Zone preference after a vend is set to no preference, align is on (tried off as well) and the delay is at max for the drum. Thought the unit was possibly losing its position, which led me to replace the parts mentioned. I can stop the drum in different zones after it rehomes, it just re-homes anywhere from about 25-75% of the time you try to choose a selection. Most likely will have main board Monday, and will have a better look with the turret out as well - I did look at the bottom of the turret as best I could to see if something might be triggering the home switch at an inappropriate time, which might make it reset that circuit, but haven't found anything there - have also tried re-positioning the home switch and experimented with various stop pin adjustments every way but sideways with no luck..... I will let you know what I find, have a few more things I may experiment with in the program as well, but I am definitely open to suggestions. Thanks again AZ, appreciate all the info that you and others share on this site

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Corrupted E-Prom may be the problem and would be the cheapest  to replace. Have you replaced lights? Check your cord for ground and check power in wall to make sure it is grounded properly. Loosen grounds and retighten them. Is the water drain hose clear and not dripping down in the bottom of turret area? Or maybe dripping down into power supply? Since it never says can't find home makes me think that even the service switch could be bad. The turret is not to heavy if it is empty on the 432. Sounds to me it is a communication problem more than a hardware problem at this point.  

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I ran into a 431 just yesterday with similar issues, and discovered that the screws mounting the motor were loose. Maybe check those? Also, check the nylon wheels under the turret. It usually takes way more time for those to get worn, but if you're grasping for straws...

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  • 2 weeks later...

Finally have this troublemaker back at the shop, but haven't found the problem yet. I have replaced the main board and eprom, as well as removed the turret, wheels all appear ok, and made sure stop pin bushing is tight. Drain tube clear, no water in turret area, motor and stop pin assemblies are both tight, removed the lights and replaced. Tried changing trays to various compartment values in the program, problem still persists,.... still have many things to check on this beast - will update after further investigation, Thanks again for all your suggestions, much appreciated.

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  • 6 months later...

Still sitting in the back of the warehouse, I'll get to it eventually.........yes, tried a known good main board, as well as a ram clear. Was thinking about using it for target practice.....I will try to get to it soon, so we all know what was going on with it.

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Perhaps low voltage is causing the machine to lose its place. Try disconnecting all non-essential items like lighting, card reader, door blower. Remove the turret to be sure nothing is under or behind it to cause drag. Perhaps when the door is closed something is binding the turret. Pull all interlock switches and see if it does this with the main door open (machine thinks it's closed).

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I pulled the turret, on location and in the shop, and found nothing loose, cracked, or binding. Turret spins freely with stop pin pulled....also changed service switch, as well as tested with door open/interlocked as lacanteen mentioned, as I too thought the turret may be clipping the door somewhere. So I moved it to the back, ordered some parts for it, and rebuilt a 431 we had for my backup. As many of you know, small businesses require you to wear many hats, and that's why I haven't had time to further dig into this machine. Remember disconnecting lights, don't recall 100% on the blower, but know I disconnected the power to the ballasts at the time.

 

I am leaning towards the mechanical side of it right now - just seems the electronics are functioning, yet receiving signals that are perhaps not what they are expecting, thus the reset......wondering if the clutch on the turret motor could be hanging enough to mess up the stop pin timing, thereby keeping the opto wheel signal active when it should be stopped.......the solenoid disengages and covers the stop opto properly, if I remember correctly. Will probably change motor and gears and see if that does it

 

We'll see how this all shakes out, because, after all, sometimes we can overthink ourselves.....btw I seem to remember a small board on the back of the main board mounting assembly, but never traced it - anybody out there familiar with it? Planned on checking that out as well - may be time to find a few hours to play with this hemorrhoid again.....

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  • 2 months later...

Finally got a little time to look at this thing, changed the drive coupling first, since the old coupling looked a bit rounded in the arch compared to the new one. Also just wanted to try one thing at a time to help narrow it down, and there just seemed to be excessive play when the turret was locked. So far,unit has behaved perfectly, been testing for a few days now.....will let you know if it acts up again -  thanks for all your assistance everybody, much appreciated!

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That could have very well been your problem.  The turret is very sensitive to its position so if there is too much play in the drive coupling and bushings it will screw up the turret position and it will not find home or always be hunting for home.

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