(Topic ID: 207376)

Flash Gordon Switch Matrix issue


By Madmax541

1 year ago



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  • Latest reply 1 year ago by Madmax541
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#1 1 year ago

I am in the process of completing a PF swap on my Flash Gordon.
Switches would correctly prior to PF swap.
Have a switch issue for the following switches on the same column, SW don't register

Sw #12 Right Side lower Target wire colors are Brn/W ORG
Sw #15 Right Side Upper Target wire colors are ORG/Blk ORG
Sw #14 Left Side Flipper Feed lane wire colors are W/Brn ORG
Sw #13 Right Side Flipper Feed lane wire colors are Brn ORG

Common point for all SW is A4J2-2

Performed SW Test - no detection
Check continuity between A4J2-2 and orange wire on SW. Continuity is good
Check for diodes on switches shorted - no shorted diodes
All SW have 1N4148 diodes.

Any thoughts greatly appreciated.

#2 1 year ago

Are the switches original/untouched? Or did you remove or replace the switches during the swap?

Try a jumper across just the wires (Bypassing the switch and the diode) to see if they respond.

#3 1 year ago
Quoted from CactusJack:

Are the switches original/untouched? Or did you remove or replace the switches during the swap?
Try a jumper across just the wires (Bypassing the switch and the diode) to see if they respond.

SW are original untouched during swap.

Jumpering across wires activates SW and they read correctly in SW test.

#4 1 year ago

So, they work (Appear correctly) when you jumper across the solder lugs at each switch? But don't when you manually close the target?

If that is what is happening, it sounds like the diodes are shot. You can jumper across just the diode and verify that the switch responds (make sure no drop targets are down or can get ghost switches appearing). If the switches work when the diode is jumpered, the diodes are either bad, or installed in the wrong direction.

#5 1 year ago

Since its only four switching diodes I replaced all four diodes.

No change, still no detection in the SW test.
Diodes were installed correct.

Any other thoughts?

#6 1 year ago

Well, there is a 0.7 voltage drop through a 1N4148 diode. Did it work when you jumpered past only the diode?

With that slight voltage drop, it is possible that a weak output from the PIA (Through the connector) could result in a return signal being too weak to trigger the input to the PIA. If it has IDC connectors (The kind where the wire is simply stamped down into the V of the pins) one might be pulling up. Otherwise, it could be a bad PIA. You might want to swap U10 and U11 and see if the symptom changes.

#7 1 year ago

Are you sure you have the wires correct? The diode band goes to the row side.

#8 1 year ago
Quoted from BigAl56:

Are you sure you have the wires correct? The diode band goes to the row side.

Attached pics below showing orientation of diode. Flipper inlane sw and stand up target on lower right of PF.

Quoted from CactusJack:

Well, there is a 0.7 voltage drop through a 1N4148 diode. Did it work when you jumpered past only the diode?
With that slight voltage drop, it is possible that a weak output from the PIA (Through the connector) could result in a return signal being too weak to trigger the input to the PIA. If it has IDC connectors (The kind where the wire is simply stamped down into the V of the pins) one might be pulling up. Otherwise, it could be a bad PIA. You might want to swap U10 and U11 and see if the symptom changes.

All connectors on MPU have been repined.
Switch out Alltek MPU with another known good working MPU from another game.
SW still don't register in SW test mode.
Checked continuity between common side (orange wire) and A4 J2-2 on the MPU.

Any thoughts?

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#9 1 year ago

Diodes look oriented properly but I can't tell for sure if you have the wires on the right leaves. If you short out the diode and close the switch does it work?
Either the diodes are bad or the wires are not soldered to the correct leaves.

#10 1 year ago

Common wire on all switches is non band side of diode.
In sw test jumpered to bypass diode, no detection.

Compared wiring to another FG PF and it matches

Any thoughts?

#11 1 year ago

Would it make sense to disconnect orange wires (common in sw column) and jumper one at a time to see if I get detection in sw test mode?

#12 1 year ago

Are there any other switches that work which are on that same row or column as the 4 that don't work?

#13 1 year ago
Quoted from CactusJack:

Are there any other switches that work which are on that same row or column as the 4 that don't work?

According to the schematics in the manual these are the only four sw on that column.

#14 1 year ago

Any other thoughts?

#15 1 year ago

No. It doesn't make sense that the switches function and appear when you bypass each diode. That makes it sound like it is:

1. The switch matrix interface chips on the MPU (you say its a working Altek)
2. A weak connection from the Connector on the MPU to the Playfield.
3. An almost broken wire on the playfield (like there is just 1 strand of wire left connected).
4. The diodes are in backwards or the strobe and return wires are reversed at each switch (were working prior).

Sorry, but I am out of ideas. I would be looking at the signals with a scope. Both at the switches themselves, as well as the strobe outputs and switch returns (with a switch closed) at the MPU board ICs.

#16 1 year ago
Quoted from CactusJack:

No. It doesn't make sense that the switches function and appear when you bypass each diode. That makes it sound like it is:
1. The switch matrix interface chips on the MPU (you say its a working
Yes switched out with Alltek from working Fathom
2. A weak connection from the Connector on the MPU to the Playfield.
I verified continuitity between MPU and PF for common orange wire only
3. An almost broken wire on the playfield (like there is just 1 strand of wire left connected).
Solid wire connections
4. The diodes are in backwards or the strobe and return wires are reversed at each switch (were working prior).
I didn't unsolder wires from sw when doing the PF swap. They worked prior.
Sorry, but I am out of ideas. I would be looking at the signals with a scope. Both at the switches themselves, as well as the strobe outputs and switch returns (with a switch closed) at the MPU board ICs.

I will double check the items you have listed, also verify will verify the pin out of the connectors.
Just thought of connectors, they were repined during restoration.

#17 1 year ago

Provided answers in the quote

#18 1 year ago

Did some more testing tonight.
1) Verified all wires are in J2 Connector are correct.
2)Ohm out all sw to verify continuity by closing the SW.
3)Verified J2 connector pins have continuity to PF.
4) on PF stripped back common source wire to all SW to make sure had a good condition and jumped over to the SW. Still no detection in SW Test.
Don't have a scope only DMM.

5 months later
#19 1 year ago

Did you ever figure out this issue, I'm having the same issue on J2-1.

#20 1 year ago

Yes it was a short that was caused by PF rotisserie. Once game was dropped into cabinet issue went away.

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