Black Pyramid
Bally, 1984I've got a Bally Black Pyramid game with a non-firing solenoid on the right side bumper/thumper. The bumper will score accurately but solenoid does not function. Left side works perfectly. Can someone please tell me which transistor (Q1 thru Q19) is associated with this (right-side) bumper solenoid? Also, any advice from anyone who has had a similar problem would be greatly appreciated!
Enter test mode with the little red button inside the door and let the solenoid test run. Is that bumper the only one affected?
A3J5.9; Q9
If a coil is not locked on, you can test it's solenoid driver board from the transistor to the coil, with the game on and in "attract" mode, attach an alligator wire and clip to ground in the backbox. Momentarily touch the other end of the alligator clip to the metal tab on a solenoid driver board transistor.The coil that is driven by that transistor should fire. *Note this doesn't actually test the transistor itself*, but just the path from the transistor to the coil. Just be careful not to short anything while you're doing this. You should be able to narrow down your issue that way.
Had a bad stomach bug over the weekend and didn't feel like working on Black Pyramid until this am. Anyway, as "mbaumie" had suggested, I hooked a jumper wire to ground and touched the tab of the solenoid's transistor (Q9 - many thanks again to "cody_chunn" for providing that info). The solenoid for the upper right-side bumper fired correctly! OK, what's next? Is there anyway to test that Q9 transistor while it's still on the board? I sure appreciate the help.
Yes. Briefly connect at jumper from TP6 to the base of Q9. This will probably be easier at CR9. Tap the jumper from TP6 to the LINED side of CR9. The solenoid should fire if Q9 is good.
Quoted from cwvet:Cody, I did that test (TP6 to CR9) and the solenoid fired so I understand that rules Q9 out as the villain. How about the diode itself (CR9) or did this test rule that out as well?
Not so fast.
That test is just to confirm you have continuity from Q9 to the playfield solenoid.
Q9 can still be failed or have a broken lead. Or have bad predriver.
The technical approach would be to start at the solenoid decoder with a logic probe. You would put the game in solenoid test and wait for q9 circuit to start right at the 74154 decoder pin. If good there, you go to the predriver. If good there you go to the main driver (q9 in your case).
If you just want to take a shot at it. I would start with main driver transistor.
Quoted from barakandl:Not so fast.
That test is just to confirm you have continuity from Q9 to the playfield solenoid.
Q9 can still be failed or have a broken lead. Or have bad predriver.
This wasn't the ground-the-tab test. It biased the driver transistor ON, so the driver Q9 is working.
Now momentarily connect a jumper from ground to U3 pin 3. Just a quick tap. Does solenoid fire?
OK, so problem is upstream: U2, J4, MPU J4...
Do you have another SDB to swap in to verify that U2 is bad?
If not, like Andrew says, it's time to break out the logic probe.
Logic probe? You guys are talking things a step ahead of my basic (and very dated) electronics knowledge. So let me ask it this way....what would be the most likely component to be causing the problem that you would replace first, second, so on if you were me.
If you are comfortable doing it, swap U10 and U11 on the MPU board (careful not to bend and legs underneath), and reseat J4 on MPU board and the two connectors on the right side of the solenoid board.
I hate to suggest replacing a part without confirming it's bad, but U2 on the SDB, a 74L154 is suspect.
Quoted from cody_chunn:If you are comfortable doing it, swap U10 and U11 on the MPU board (careful not to bend and legs underneath), and reseat J4 on MPU board and the two connectors on the right side of the solenoid board.
I hate to suggest replacing a part without confirming it's bad, but U2 on the SDB, a 74L154 is suspect.
Something to try....
game off. DMM set to diode test. Red lead on ground. Black lead probe u2 decoder outputs. Compare readings from working decoder output pins to the non working one. Not a fool prof test, but could indicate a problem if it reads OL or 0.00.
Problem solved. Turned out to be that Q9 was apparently working only intermittently (the transistor worked when earlier I tried a brief contact between TP6 to Q9's base as suggested by Cody. While I had the board out taking care of cap upgrades (C23 & C26) I figured "what the heck" and went ahead and changed out CR9 and Q9 (I had already added a socket and replaced U2 hoping that would take care of the non-firing solenoid problem but it didn't). CR9 ended up testing test good out of circuit so I ruled that diode out as the culprit. Replaced Q9 with a TIP102. Solenoid for right bumper-thumper works great now. I sure appreciate everyone's suggestions on troubleshooting this problem (I learned alot).
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Columbia, MD