Classic Stern multiple switches firing

Have an issue with Stern Quicksilver, if i drop the middle right drop target, it accumulates points continuously until the 3 bank of targets resets.

Put the machine in switch test, and when i hit the middle right drop target switch (31), switch 23 also appears on the displays (which is one of the drops on the left bank of targets). They both share a brown yellow wire. I tested the diodes (in circuit on both sw 31 and sw 23, and both test good - and the same as the other diodes nearby. When i test sw 23 by itself in switch test, it only fires itself.

I also noticed that standup target sw 15 in swtich test also fires sw 7 (tilt) - but it doesn't tilt during a game. Interestingly, sw 15 also has a brown/yellow wire.

Any suggestions on where to from here - should i replace the diode on 31 even though it tests OK?

Even more bizarre is another guy is having exactly the same issue with a Meteor - Sw 31 is causing sw 23 to fire, as well as sw 7 occasionally!

#2 5 years ago

???

robm

Pinside member

Further info - i went into switch test then removed plugs J2 and J3, when jumping the appropriate row/column pins on J2, the problem disappeared - ie: confirming that it is a wiring/playfield issue, not an MPU issue.

#3 5 years ago

237

slochar

Pinside member

7y 86,550 6,913

OP
Quoted from robm:
Further info - i went into switch test then removed plugs J2 and J3, when jumping the appropriate row/column pins on J2, the problem disappeared - ie: confirming that it is a wiring/playfield issue, not an MPU issue.

Time to go over all your playfield switches carefully. Make sure nothing is shorting to anything else like ball rails, drop banks, posts, lamp sockets, etc.

You could just replace the diodes it's not like they cost a lot. If they're the glass envelope ones they seem to fail more so on that era game than a 4001/4 would.

#4 5 years ago

???

robm

Pinside member

Replaced diodes on all switches in the brown/yellow row under the playfield - no result. I didn't bother doing diodes in the cabinet switches (tilts), as i disconnected J3 which are those wires and the problem remains.

Also removed the brown/yellow wire from each under playfield switch one by one and the switch test still gives multiple hits of different switches each time (was trying to isolate it to a single switch).

Have inspected all those switches (7,15,23,31,39) with the brown/yellow wire that are firing multiple times when one is pressed, and can see no metal parts above or below the playfield around them! Starting to go nuts with this one as i don't know what to try next.

Am i heading down the wrong track just looking at the brown/yellow wire which is for row 7 - do i need to trace the corresponding column wires for each switch in that row?

#5 5 years ago

TPR

frunch

Pinside member

I think i might have found the solution: look for a capacitor on the switches for the "left middle stand up target" and "top rollover button"

Cut the caps off and try the switches again. Probably a shorted cap that's interfering with the other switches on the same row.
945896879.png

#6 5 years ago

TPR

frunch

Pinside member

Also, it appears the tilt switch is on the same row, I6 (though it uses a different wire color, making things a little confusing without looking at the schematics) ...which would explain why it's also coming up sometimes as well in switch test

1766108885.png

#7 5 years ago

???

robm

Pinside member

Quoted from frunch:
I think i might have found the solution: look for a capacitor on the switches for the "left middle stand up target" and "top rollover button"
Cut the caps off and try the switches again. Probably a shorted cap that's interfering with the other switches on the same row.
[quoted image]

OK, snipped both those caps, no change.

#8 5 years ago

???

robm

Pinside member

Further update. Even though i thought it was not MPU related (due to pulling J2 and jumping pins and it testing fine), i put in an Altek board from my Paragon, and it works fine!!!

So now an assuming its an MPU issue - i guess i will looking at J2 where the brown/yellow wire goes, but not really sure what i am looking for!

#9 5 years ago

TPR

frunch

Pinside member

Perhaps a PIA or PIA socket issue? U10 and U11 can be swapped to see if the problem moves.

#10 5 years ago

???

robm

Pinside member

Quoted from frunch:
Perhaps a PIA or PIA socket issue? U10 and U11 can be swapped to see if the problem moves.

Unfortunately problem stayed when i did this...

#11 5 years ago

TPR

frunch

Pinside member

Is it an original or aftermarket mpu?

If original, was/is there any battery corrosion on the board?

#12 5 years ago

???

robm

Pinside member

Had some other suggestions that it could be a fault or ground short on the MPU, was told to lift one end of C25 on the MPU which is the one that the brown/yellow wire goes to after the header pins and resistor.

When i lift one end of this cap, the machine plays normally (ie: doesn't rack up points hen you drop target sw 31), HOWEVER, in switch test, sw 15 still triggers sw 7 as well (the others in that row all test fine).

Apparently C25 is 390 pf, i only had a 470pf available, and used it and it went back to the same issue with scores racking up when you drop the target sw31. Lifted the end of the cap again, and it plays fine.

Any other suggestions on what to look for or replace on the MPU?

#13 5 years ago

???

robm

Pinside member

Quoted from frunch:
Is it an original or aftermarket mpu?
If original, was/is there any battery corrosion on the board?

Original MPU that has been repaired and it looks to be a pretty good job of cleaning up corrosion.

#14 5 years ago

PIP

Quench

Pinside member

8y 114K 8,039

OP
Quoted from robm:
Any other suggestions on what to look for

This issue usually happens from battery corrosion crud that's become a resistive short across switch strobe or return lines.
With J2 and J3 disconnected from the MPU board, measure the resistance of the strobe and switch return lines at pin header J2 with respect to ground. They should all read in the vicinity of 57k ohms.

Post clear high res pictures of the MPU board if you can.

#15 5 years ago

???

robm

Pinside member

Problem solved! Replaced R40 (57k) and all is good.

Thanks for the help

#16 5 years ago

TPR

frunch

Pinside member

Good job!

Don't forget to replace the caps on those switches under the playfield. I'll typically replace all of them while I'm down there. The switch matrix on the schematic shows which switches use a cap.

#17 5 years ago

CAD

cottonm4

Pinside+ Addict

Wichita, KS

10y 148K 16,593 10 23

OP
Quoted from robm:
Problem solved! Replaced R40 (57k) and all is good.
Thanks for the help

How did you figure it was a resistor, please?

#18 5 years ago

???

robm

Pinside member

Quoted from cottonm4:
How did you figure it was a resistor, please?

I can't claim credit- someone on Aussie Arcade suggested i look for that - as well as someone in this tread. Basically i started tracing components back from the pin where that row of switches went to on the MPU

#19 5 years ago

CAD

cottonm4

Pinside+ Addict

Wichita, KS

10y 148K 16,593 10 23

OP
Quoted from robm:
I can't claim credit- someone on Aussie Arcade suggested i look for that - as well as someone in this tread. Basically i started tracing components back from the pin where that row of switches went to on the MPU

Thank you. That is good info to know.

2 years later

#20 2 years ago

WOZ

woz

Pinside member

14y 77,050 1,866

I just spent last night troubleshooting a Quicksilver with almost the exact same symptoms.

Game had been playing great for the last week - no problems at all except for some lamp issues. I installed freeplay ROMS and again, it played fine. I left the game on for a couple of hours the other night and then the game started just randomly tilting during play. Then it started sometimes continuously adding points. Weird.

In switch test mode the following was happening:

SW15 (Left Middle Standup) registered SW15 & SW7 (Tilt)
SW23 (Centre Drop Target- lower middle) registered SW23 and SW15
SW31 (Right Drop Target Middle) registered SW31 and SW23
SW39 (Top rollover button)registered SW39 and SW31

Almost teh same situation as the OP, but not quite.

All the switches are on the same row. Each switch would register its own switch and the switch in the previous column on the same same row.

I thought it may be due to the freeplay ROM so cleared all the audits - no luck. Swapped the 6821's over - no luck.

Unplugged the cabinet switch matrix connector (J3 on the MPU) and the fault cleared! Yay must be something on the coindoor. I couldn't find any issues with the coin door or tilt switches.

Set all the DIP switches to OFF and checked all diodes - no luck.

I'd checked all the diodes and capacitors on the switch matrix and they all tested ok. I then checked the matrix for shorts between rows and columns and didn't find any issues.

I was stumped, so started measuring resistances to ground on the MPU and found that Row 6 was measuring a lot higher (3x) than the others. Hmm. At this point it was late and I was ready to stop for the night. I then came to Pinside and found this thread. Almost exactly the same issue. I just pulled the MPU out and R40 was measuring 182K instead of 56K. What are the chances the same resistor should fail and go high resistance? I changed the resistor and it fixed the issue.

So thanks to robm for starting this thread and documenting the repair process.

BTW I found that if all the DIP switches on the MPU are OFF, the game boots straight into test mode. That had me confused as I though t I still had switch matrix issues.

IMG_20211102_164233 (resized).jpg

#21 2 years ago

RIK

Rikoshay

Pinside member

9y 46,900 1,508

the DIP switches all off and then powering up and the game going into audit/test mode is normal, change just one switch and it will boot into attract mode.

#22 2 years ago

???

robm

Pinside member