Sttng right cannon home/mark switch issue

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The right cannon on my sttng does not align properly most of the time. It gets stuck about 2cm from where it should so balls get stuck until a ball search. Narrowed it down to some odd switch behaviour with the home and mark switches as can be seen here:

The mark switch most often triggers both switches to close and so the cannon stops before it hits home. You can see that there's a bit of flakiness going on somewhere too.

Any idea what this is before I start soldering? Diode? Switch?

Cheers
Steve

 

[BigIan]

Have the cannon looms ever been changed ? I would start with them , they cause all sorts of weird problems

 

[sclose]

I think so yes but not by me, there's rubber shrinking been added at some point. It seems it's islolated to these switches underneath the playfield which (as far as i can tell) have nothing to do with the looms. But yes, I get what you're saying - weird problems. Could well be the looms. I'm just not wanting to get into that chasing-a-problem-round-the-table situation!

 

[Moonraker]

I would look for a broken diode... probably on the switch that's not being activated.

 

[cmrl9]

I had a STTNG the canon looms can cause all sorts of stupid and strange problems that have no logic to it being related. Changes these first, they are about £30.

The canon has two pairs of opto one on each, if they are a yellowish colour change them they will be original and 30 years old. You have to desolder the wiring loom from the opto's and flasher, so you might as well change the opto as they are only £8 ish each.

My STTNG faults related to three things:

Wiring loom on canons
Opto's
Fliptronics board

Took me about 6 months of troubleshooting to get to the above and rebuilding the machine.

 

[cmrl9]

And try the switch diode

 

[sclose]

Just in follow up to this. Mark switch diode replaced and all good now. Thanks for the pointer!

 

[cmrl9]

Glad you fixed it