Stern T3 - ONE switch works in TEST but NOT in gameplay

[Wotto]

Hi all

Title states the issue.

I have reseated connectors , I have tested the diode ( leg off ) and its fine.

ALL other switches in the game are perfect in test and gameplay.
Obviously that mean all the switches in that particular row work fine so I cant see how it would be a board component causing this issue if they all work?

This one switch just 'stopped' registering in gameplay.

I have noticed that 'sometimes' in TEST that it registers more than once real quick - but MOST times in test it registers as per the times I press it..........just adding that little bit of info in case it helps diagnose at all

I am sure the 'more clever than me' ones of you will have some advice 

[Wotto]

I have also done a continuity test from the wires switch to their applicable place on each connector and its fine too.

In TEST mode , the swithc registers if I press it with my finger or if I roll the ball past it - either way works fine.
In gameplay - neither work.

[Wotto]

So I remove the board - multimeter across the few components related to this switch - all appear OK.

Put the board back in and now the game is not coming on............just blinking on and off and the relay on the Driver board is clicking away and the red led at 204 ( blanking ) is flashing in time with the relay.

Please place 1000 of these  right here !

[Wotto]

Back to just the switch issue 

[Wotto]

Edit - I replaced the actual switch itself - only to get the exact same result - new switch, works in test - doesnt work in gameplay.

I am fast running out of ideas 

[Strangeways]

I was about to suggest using an alligator clip to short the switch, but since you just swapped them over, it is back to the wiring.

is it one of the RED square switches ?

[Wotto]

No mate - a 'cherry' style switch on the right ramp with an actuator arm hanging off it.

[Marty Machine]

Try removing/replacing the tiny filter capacitor on the switch row/column in the switching matrix.

During test mode, ONLY the switch matrix is running/repeating, giving it a more efficient scanning time to read the switches, so switches will all work more efficiently.
In game mode, ALL the matrixes/solenoids/scores/buttons are being read/updated repetatively, thus less time-slice is used to process each matrix.
So, with a slightly dodgy matrix cap, it will be partially filtering/missing the switch closure pulse, therefore not responding in gameplay.

Since you've now replaced the switch itself, it's pointing more to the matrix again.

MM

[Wotto]

Marty - that sounds logical - but is in a territory I am completely unfamiliar with.
I wouldnt even know where to start with that to be honest.

[Wotto]

Hey Marty  ( and / or Nino )

Is it possible to test a capacitor in the board with the MM on Ohms and touching each leg and at least see a rising value?
Does this ( possibly stupid ) question make any sense?

[Retropin]

The capacitor will be a small ceramic type.. little yellow one probably, value around 10pf.. it takes ripple and noise away from the chip. You cant test these in board... you cant test any cap or resistor in board... look on the schematics for which cap is tied to the chip and just replace.. Jaycar will have them.

[Wotto]

Hi all

Working on Martys theory and Gavs information - please see below if you feel you could/ would like to assist.

Firstly - I assume that these are the capacitors you are talking about ( this style , not this particular batch )




If so - could someone please take a look at this large image of the schematics and tell me which one it is I would need to swap out for a new one?
I have highlighted the 2 connectors on the right in orange. You will have to click on this image - be taken to anothe rpage, click the magnifying glass on lower right and it re-opens in another window - then click same lower right mag glass in THAT window and the image will be massive



Many Thanks if anyone can assist further 

[Retropin]

Id be replacing both C407 & C224.. these are the caps on input/output but there is another cap tied to the chip itself that takes away ripple noise.. id be replacing that also.
If you look at U204 in your pic, directly below is cap C272.. this is the noise ripple cap for that chip and will be tied to the earth on the chip.

You have a chip for switch rows and a chip for switch column.. we don't know which is the one we want so replace the filter caps on both of these.... so 4 caps all up to be replaced, this will completely cover you.

Just to add that the caps are Tantalum.. these quite often fail and can be replaced with a simple ceramic 0.01Uf or whatever the value was

[ddstoys]

Have you tried a factory reset Wotto?   

[Strangeways]

Have you tried a factory reset Wotto?   

+1

It has been a while since I worked on a later Stern, but I have a question - The Stern switch matrix is not like the older style with diode and capacitors to detect switches like targets. Those caps are mounted on the switches themselves. I would be ruling out wiring and simple fixes as Daniel suggests before touching the board.