Ticket zone claw grabber troubleshooting help please - Page 1
Forum section: electronics / repair

author: Somedre
author_rank: Newbie
timestamp: July 16, 2019, 04:08:19 pm
content: Hello all. First time posting.I work as a technician at a gaming arcade, i am entirely self taught.I have been struggling to diagnose an issue with the solenoid on one of the claw grabbers not closing despite having 50v presentThe machine is a ticket zone grabber built by coast to coast amusements. The manual is lackluster and I was unable to find any board diagrams.What I've done so far:The coil is rated for 48v, it has continuity, there is a bit of discoloration in the material covering the coil.It has an internal resistance of 0.24 ohm, I have tested it on a separate 12v psu and it does pull the plunger in, slowly as one would expect.I have tested a separate working claw on the same machine and it still doesn't close.On the machine.I have tested continuity from the claw down to the board, all fine.As mentioned previously, there is power, when it is supposed to be in the closed state there is roughly 54v coming from the board without a load and over 50v with a claw attached.I had started tracking the paths on the board starting from the output pins of the coil until my head combusted, I will get back to it if I have to.I understand that the issue likely lies somewhere in the machine rather than with the coil itself.With my extremely limited knowledge of electronics all I can think of is there could be some component that is allowing voltage to be there but no current to flow. If even possible.Has anyone seen anything similar, could it actually be a board component or is it more likely to be psu related?Please let me know if you can think of something, I will try to provide any additional information that I can. I only have access to a digital multimeter as far as measurements go.Any advice will be greatly appreciated . Thank you.

author: mikerj
author_rank: Super Contributor
timestamp: July 16, 2019, 04:19:49 pm
content: Quote from: Somedre on July 16, 2019, 04:08:19 pmThis simply can't be correct, it implies the solenoid would require 200 Amps at it's 48v rating, giving almost 10kW power dissipation! I would expect resistance to be in the tens of ohms at least.Is it possible the solenoid is internally shorted and there is some kind of built in overcurrent/thermal protection?

author: Somedre
author_rank: Newbie
timestamp: July 16, 2019, 04:47:57 pm
content: QuoteI really am not sure, the coil itself looks very basic, I am back at work tomorrow so can post a photo of it, I got the rating from a technician who works for the distributor as there isn't anything written on the coil.I will test the resistance again tomorrow. While I don't know the maths the numbers do sound outrageous.Also would a solenoid still close if it's internally shorted? I genuinely don't know

author: SMdude
author_rank: Frequent Contributor
timestamp: July 18, 2019, 01:13:20 pm
content: Given that you have tried another known working solenoid and it still didn't work, I think your solenoid is ok.Compare the resistance between the 2, they should be close and probably more like 20ohms >If you measure the voltage across the solenoid terminals while it should be activated, what do you get?Also, set your multimeter to measure current and put it in series with the solenoid.It just seems impossible for you to have 50v across the solenoid and it still not pull in, especially when you have applied 12v and it does pull in, all be it slow (this is normal for this type of machine right??)If you can post some photos of the solenoid drive circuit that might also be helpful.