Duct keys opening and closing on their own

Hi,

I have a 20 or so year old Heidelberg 72 and recently the keys randomly open up or shut down on the run. This happens on all units , though it seems to happen more often on some keys than others. It doesn't happen all the time, or to all at once. A couple of weeks can pass with no probs then a few keys on a duct will open up or shut down on the run. The display on the console doesn't show this. The display continues to show as set. The keys have been cleaned, so it isn't dried ink etc. It sounds to me like a pcb. I have two presses the same age so if it is a suspect board I could swap it and see if the fault shows up on the other press. I'm not sure where to start to look though. Any ideas?

Thanks

 

One of the reason is bad potentiometers.

 

Thanks for your interest aqazi81
If it was one key, maybe, but this prob has happened out of the blue on all ducts. Can't see a bunch of pots all going at once.

 

this might sound simple but I have seen this happen when the keys are sticking on your cpc check these first

 

Thanks

 

I've also seen the cpc switches stick but when that happens the pot. will follow the ink key. The OP mentioned that the display on the console does not reflect this. I lean towards the board.
On a future preventative note I'm a firm believer in exercising the keys on a regular basis. Ive found that running all keys through the full length of adjustment from fully closed to fully open on a fairly regular basis will keep things from binding up.

 

Many thanks. I am taking all of this on board and I am amazed at how helpful everyone is.
Pete