I have a Gottlieb Volcano (1981 system 80 2nd Gen) acquired about 9 years ago. Way back in 2012, I did the ground mods, removed the battery, cleaned up the MPU, as well as various repairs getting the game mostly playable. However, I did not fix any loose connections and the game stopped booting very soon after 2012. I recently got back into it and tracked 99% of the present issues to loose pin connectors on the power supply board. I installed all new pins and connectors on the power supply. I also cleaned up all the edge connectors and will be replacing those at some point soon with the new solder-on connectors from Docent Electronics (https://www.docentelectronics.com/httpdocs/AmusementGames/Pinball/Gottlieb/system%2080.htm). Right now, the game is playable and boots up correctly about 95% of the time. The other 5%, there might be a sound card anomaly that resolves when the game starts, or the shoot again lamp is on without power to the playfield. Again, I think replacing the edge connectors will finally resolve this.

Anyway, one of the issues right now is the right-hand ball-gate functionality. There is a round yellow target in front of a green playfield light called "open gate". Then on the lower-right side of the playfield there is a chute with a green light called "gate open" and a ball-gate. The Volcano manual does not describe the proper sequence of events for this part of the game.

I assume that when the "open gate" lamp is lit, that you are supposed to hit the yellow target. Then when the yellow target is hit, the ball gate opens and the second light "gate open" lights up? Is this correct? Mine is not operational for some reason.

When all 5 of the drop targets are hit, the top "open gate" light comes on, but hitting the yellow target does nothing. The gate never opens at any part during the game.

Troubleshooting:

1. I have verified the ball-gate solenoid is good by jumpering power to it. It opens the ball-gate and the second light comes on when this gate is activated.

2. I have verified that there is 38 VDC on the ball-gate solenoid during game play, which matches the schematic.

3. I have verified continuity of the solenoid circuit back to the fingers on the output of the Driver board.

4. I triggered the ball-gate solenoid by applying 5 VDC to the base of the transistor (Q15). This transistor also tested good as per DMM test procedure.

So now I suspect that maybe one latch inside the 74175 chip is bad, but this is only an assumption. Can I test this further to be sure? How do I know the switch input side is not the problem?

5. I am reading something like 4 or 5 VDC on both sides of the switch for the yellow target when the corresponding lamp is lit.

6. I jumpered across the switch during game play and it makes no difference, the ball-gate is never activated.

7. I have continuity from the switch at the yellow target back to the J6 connector at the MPU.

Is there any additional specific tests I could do before installing a new 74175 chip? I'd rather not change this chip if not necessary. Thank you!

Thank you for responding...

The lamp test is Step 16 and the "gate open" lamp does not light up because it is apparently not part of this test. It only lights up when the ball-gate is activated and closes the switch at the gate.

The solenoid test is Step 17 and only specified to cover the Subway Ball Release, Top Drop Target Bank, Subway Kicker, Right Drop Target Bank, Knocker, and Outhole. None of the other solenoids including the ball-gate are part of this test.

The switch test is Step 18 and it only checks if all switches are open during the test. It returns a "99" if all switches are OK (open). My test returns a "99".

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Re-reading the manual, I see that the ball-gate and ball release are supposed to be part of Step 16 Lamp Driver Test:

Quoting the manual:

"Q, T, M, & B relays and coin lockout coil are pulsed. All controlled lamps, plus the ball gate and ball release, are sequentially turned on."

Since the ball gate is not activating during this test, I assume this rules out any problems on the input side. And since the transistor is testing good, it has to be the 74175 latch, right? Or maybe I'm missing something?

Oh yes... good idea. Thank you. EDIT: This is getting even more perplexing... the yellow target's switch (#36) is not registering on the switch test.

Yes, there's a switch on the solenoid that activates the light. I can manually flip the solenoid and the light comes on.

That's what I was thinking. However, since my last post I did more testing using Step 16. While this test is working, I placed my DMM on the relevant output of the 74175 latch chip and it's toggling. A little fast for my DMM to fully react but I can see it go from low to high when Step 16 hits the ball-gate solenoid. So then I move over to the output of the transistor and look at the finger on the board... it's not toggling there and it's always showing low. Low should trigger the solenoid but...

The way it's wired as verified by the schematic, the common side of the solenoid is +38 VDC but only during game play when the "Q" relay is pulled in. However, during Step 16, the Q relay only pulls in momentarily and is not pulled in during the ball-gate pulse. So now I'm really perplexed... clearly something is wrong because the ball-gate is not working. However it's supposed to work during Step 16, but how can it when there is no +38 VDC on the solenoid without the Q relay activated?

It's not seeing the input for the switch and the output is not triggering the solenoid... two problems?

Yes, the ball-gate toggles in Step 16 when the Q relay is manually held... so apparently now I can totally rule out the output side, transistor, and latch chip.

Yes, jumping the switch does not work.

I am using Step 18 to manually test all the switches I can find.

Looks like most of the last column, which includes the yellow paddle switch, are not working....

SW06 - Left outlane rollover and the left green button - NO INPUT
SW16 - Left return rollover - NO INPUT
SW26 - Kicking target - NO INPUT
SW36 - Yellow spot target - NO INPUT
SW46 - Tilt - NO INPUT on the tilt switch under the playfield, but it registers a "46" when the lower cabinet tilt switches are closed.
SW56 - Right side green button - SHOWS "56"

I will start checking wire continuity here.

Why would SW56 in the column work and not the others? Broken common wire between 36 and 56 ? Why would the tilt switches in the cabinet show "46" but the playfield tilt is not working? Again, broken common wire between them I imagine. I will start tracing these out.

56 is the green button next to the flipper button. It works (freezes the ball shooter) and it registers a "56" when doing the Step 18 test. However, I do not like these Gottlieb switch matrix schematics... they show switch 56 in the same column as 06, 16, 26, 36, and 46 all sharing the same common wire. It does not show how the green button gets back or any of the additional connectors. Nor does it show the multiple switches that are wired in parallel. Despite the drawing showing 56 connected to the others and going to the same A1J6 pin 16, I see no continuity to this switch, despite this one working fine and registering itself on the test. No idea.

Regardless, I focused all efforts on 06, 16, 26, 36, and 46. They are all properly connected to each other, they all register zero ohms when closed, and they all have continuity to pin 16 on the A1J6 for the MPU.

There are five banks of diodes on the playfield which seem to correspond with the five rows in the matrix. I used my DMM in diode mode and every one of them checked out good.

So now I'm thinking that perhaps the #16 connection in A1J6 to the MPU board is bad or that it's the 7400 chip that receives this input.

**** I walk away from writing this reply to check one more thing... ****

The schematic shows pin 16 from A1J6 connecting straight into pin 2 of the Z14 7400 chip. I then checked continuity of the common wire on the matrix column to this location and it's no good. Removed the MPU and visually traced out the path from pad 16 and the schematic is wrong. Go figure. Pad 16 does not connect directly to pin 2 of the Z14 chip despite the diagram clearly showing this. Then I found the board's passthrough points and tested it here with the A1J6 connector plugged in and it shows continuity to the switches with the board plugged in. I put it back together and powered up. Now all the missing switches in the column are showing up on the Step 18 test, and the ball-gate is properly opening when the yellow paddle is pressed.

Same lesson learned... yet again... Gottlieb board connections suck. I will be ordering new connectors from Docent Electronics sooner rather than later.

I thank you very much for teaching me how to properly use the switch and lamp tests for troubleshooting.

EDIT: Problem came back and I found that the tiny copper trace was cracked through at the top of edge connection A1P6 finger 16 on the MPU. Fixed.