Before I sell it for scrap... KX220

I have a 20'ish-year-old Kawaguchi KX220. Kawaguchi up and left the states years ago to my knowledge. One of their lead technicians stayed back and created his own company to support the machines in the states. I have been going back and forth with him for over a year and have made 0 progress. Have tried a couple of other 'technicians' but once I lay out the entire situation *POOF* they are gone like a fart in the wind.

So that's the back story...

As I was browsing the forums trying to soak up any and all good information I could as I often do (self-taught molder, would never claim to be an expert) I suddenly realized that perhaps I could post this here and get a decent response so here goes:

When I first boot up the machine none of the potentiometers will register. This means that the mold opens until it literally hits the wall. The machine will charge until the barrel is max capacity... etc. Without the potentiometers to define its limits it just goes until it can't. Needless to say, it won't operate that way even though all of the other functions on the machine work fine.

Most days I power up the machine and after some time (2 minutes to 2 hours) the alarm sounds and I know that it's working, that all of the potentiometers are functioning properly even though the alarms are specifically for the potentiometers. Lately, it's doing something new where they will suddenly stop registering which of course ends any chances of running parts on that machine.

So I know it sounds strange. To myself, and to the tech it seems like it should be a board and we even know which board it should be. We've tried a replacement board though, and I've even sent him the entire rack to him for testing and they all tested OK.

Pondering a new machine but I hate leaving problems unresolved and the machine actually runs well when it runs... Not to mention the cost of a new machine.

I thank you in advance for any sort of insight you can provide and if you can't provide any, I still appreciate you taking the time read this.

~ Huckage

We have some old battenfelds, 1985 models. - On occasion I strip and clean those potentiometers ....very carefully. have you swapped the potentiometers with other units?

Unfortunately yes I have already tried that with no luck. I appreciaciate the response, however. Thank you.

another obvious one is the voltage coming to the potentiometers ?

I agree with Crabstix in thinking a good direction to go is checking and making sure you have power going to each potentiometers. It would be helpful to know if you have rotary or linear pots. The inconsistency you describe also could be a poor connection, loose or loose card somewhere in the circuit for the potentiometers. Including the power supply. Since you state the problem is on at least two different pots. review your electrical drawing and see if there is a common circuit or common wire within the two pots. I would hate to see you scrap this machine so I'll check back looking for your response.

I think they work on 10V. you could try and shift the potentiometer so that it uses a different position, in other words it shifts the wear marks. It means you will have to recalibrate your positions. I hope that is clear.

I appreciate all of your responses, truly. Currently I have had the machine running for a solid two weeks with no issues. All voltage is of course reading properly as the machine is running properly. This has been the issue for nearly two years now. Sometimes it works, sometimes it doesn't, and even the Kawaguchi tech I mentioned in the first post doesn't have an answer. Keep in mind also that it isn't just one potentiometer that fails or even two. There are four and they either all work or they all don't. This is what made me think it has to be a board but the replacement board didn't change anything and the entire rack of boards tested OK. Once again I do appreciate you folks even taking the time to respond and offer your help and insight.

~