Al's Garage Band goes on a World Tour
Alvin G. & Co, 1992I've narrowed down some wires that "may" be causing my issues with Al's Garage Band.
When I test the diode on the plunger, connected as normal, with machine off, I get continuity in both directions. I understand that is not normal for a diode in the wild, however, does this seem "normal" for a diode connected to a plunger coil?
I can provide schematics if it helps.
Thanks
You are measuring the coil. You MUST disconnect one end of the diode from the coil to measure it.
For me, you have to disconnect one end so might as well just replace any suspect diodes anyway for one cent each
I have plenty of diodes on hand, was just hoping I found the culprit.
So sounds like I need to snip one end of the diode in order to check.
As it stands, connected, power off, it could/would read continuity in both directions?
Yes. The coil resistance is in the order of 5 to 20 ohms and the diode is many times higher than this so you can never test a diode in circuit like this.
Ok, thanks for the help. I'll look for another coil # first, if not found, snip it is.
Appreciate the quick responses!
No matching coil numbers.
Can I ground out a coil with no fuse? I can't run a ground jumper test because the fuse blows within a few seconds of being turned on.
Can I bypass the fuse to see if the coil will fire, or do I risk frying my board?
I was thinking alligator clip to ground/source, another to pin/trigger wire briefly.
Machine on.
Quoted from Homepin:Yes. The coil resistance is in the order of 5 to 20 ohms and the diode is many times higher than this so you can never test a diode in circuit like this.
Found nearly every diode is reacting the same way, so I'm not snipping.
I'd like to try a coil ground first.
The fewer cuts and repairs I have to make, the better!
If the diode was bad then grounding the coil won't show it. The diode is there to protect the circuitry that controls the coil. A jumper doesn't need that protection.
If you jumpered both sides, and the diode was shorted completely open, you might melt your jumper, or it might still fire the coil.
You could try unplugging the connector, putting the fuse in, and then connecting the wires in the connector one at a time to their corresponding pin on the board, see which one blows the fuse, to help narrow it down. Sometimes you can just check continuity from the pins on the board and the connector (disconnected) to ground and you might find one 'off' reading that will lead you in the right direction.
So
1. Power off
2. Connector unplugged
3. Fuse in
4. Connect 1 wire at a time from connector to board.
5. Power on, hope for no sparks.
6. Rinse, lather, repeat.
Sound right?
Sorry, I'm v er y new to troubleshooting with this.
Quoted from RonSS:So
1. Power off
2. Connector unplugged
3. Fuse in
4. Connect 1 wire at a time from connector to board.
5. Power on, hope for no sparks.
6. Rinse, lather, repeat.
Sound right?
Sorry, I'm v er y new to troubleshooting with this.
I'd just connect them live, but yeah, that'll work fine. Theoretically only one of the coils or drivers is bad, so if you only have one of the coils connected, and it blows, you know that one is where the problem is
Great, I've got a plan that doesn't involve dismemberment!
Thank you, I'm off to blow my last fuse, hopefully successfully.
So weirdness,
Everything worked as it should - flasher relay and GI just made soft noise during test but that seems right.
I left the connector unplugged and exited test mode. I now have flippers!
Of note:
Earlier today I found 2 diodes too close to switches or other bare metal than seemed reasonable, so I bent them to a safer distance.
And, when I was connecting the plunger, that was the only coil to go automatically, without hitting the "start test" button. Also, it made a small spark in the connector with my probe end each time. None of the other pins did this.
I had to use a fuse from F22 for the test, so hopefully later today /tomorrow my new batch of fuses arrives, I'll load it all up, and try again.
The flippers working have me excited! 
Quoted from zacaj:Might want to invest in a circuit breaker
And better home owners insurance! 
Quoted from RonSS:And, when I was connecting the plunger, that was the only coil to go automatically, without hitting the "start test" button. Also, it made a small spark in the connector with my probe end each time. None of the other pins did this.
You mean you were just in attract mode and when you connected it it fired? But it didn't stay locked on I assume. Probably just auto-programmed to clear the shooter lane when there's not a game going
No, I was in "test" mode and choosing which coil/sol to activate.
For each of them I would attach the clip to the board pin, select the coil/sol from the menu, then attach the other end of the clip/probe to the assigned connector space. After the ends were making the connection (connector wire to board pin) I would press the "start/test" button and the item would respond.
When I did this for the plunger it fired the plunger before I hit the "start/test" button.
You are correct, it did not stay on, just fired and released.
Quoted from RonSS:No, I was in "test" mode and choosing which coil/sol to activate.
For each of them I would attach the clip to the board pin, select the coil/sol from the menu, then attach the other end of the clip/probe to the assigned connector space. After the ends were making the connection (connector wire to board pin) I would press the "start/test" button and the item would respond.
When I did this for the plunger it fired the plunger before I hit the "start/test" button.
You are correct, it did not stay on, just fired and released.
Would it then fire when you hit start
No, no plunger, but that is connector h6 which I did not put back.
I'm waiting on fuses as now F22 has no fuse (same rating as F17 which keeps blowing). May be coming today.
I'm hopeful this machine will work now, we'll see.
What about the spark from the connector for the plunger, any connection you think? Or just me with shaky hands?
Ugh.
I received my fuses, put a fuse in so all the spots were good. Started the game, and BAM! F17 blew. OK, that's fine I guess.
Couldn't test the plunger because that is associated with F17.
But now my Flashers aren't working??? The fuse F20 associated with that is fine, I pulled and tested.
Is it time to pull the board and start checking MosFets? Or does this sound like a wire issue? Or something else all together?
Quoted from RonSS:Is it time to pull the board and start checking MosFets?
That's the first thing I would have done, to be honest. Did you try the continuity to ground test on the pins? Often that can identify a bad driver circuit without the trouble of removing the board.
As for flashers, do they still have voltage?
Quoted from RonSS:I received my fuses, put a fuse in so all the spots were good. Started the game, and BAM! F17 blew.
See? Your fuse was good.
Take the now dead fuse, and solder it across a circuit breaker of same or smaller amperage.....saves you a fortune in fuses while troubleshooting
Quoted from zacaj:That's the first thing I would have done, to be honest. Did you try the continuity to ground test on the pins? Often that can identify a bad driver circuit without the trouble of removing the board.
As for flashers, do they still have voltage?
What is that test? I thought that's what I did on connector h6?
Flashers work only if I have connector h6 in, even though they are connector h7.
Quoted from vid1900:See? Your fuse was good.
Take the now dead fuse, and solder it across a circuit breaker of same or smaller amperage.....saves you a fortune in fuses while troubleshooting
Yeah, I knew the fuse (s) weren't the issue, but that's pretty funny.
Nice trick for using the bad one though, thanks!
Quoted from RonSS:What is that test? I thought that's what I did on connector h6?
Quoted from zacaj:Sometimes you can just check continuity from the pins on the board and the connector (disconnected) to ground and you might find one 'off' reading that will lead you in the right direction.
Um, so help me out here,
I'm using which setting on dmm, machine on or off, and just comparing values?
Quoted from RonSS:Um, so help me out here,
I'm using which setting on dmm, machine on or off, and just comparing values?
Machine off first. Use continuity and/or diode setting. One lead on ground, other lead check each pin of the connector on the board with the plug removed. Should all have the same reading. If any of the pins has continuity to ground, then you know that driver circuit is bad somewhere (usually the mosfet) and shorted through to ground. If you don't find any, turn game on and repeat. If you find something now, you know it's something in the signals.
But let me confirm the results of the other test: you put a good fuse in the spot that normally blows, with the connector disconnected. You turned it on, and connected one pin of the connector at a time, and none of them blew the fuse? But if you just turn it on with it plugged in, you do blow a fuse?
Quoted from RonSS:Correct.
I used clips and a probe to check each pin, one at a time, in "test" mode.
Clips, plural, *and* a probe? Should only need two of those three
Quoted from RonSS:No, no plunger, but that is connector h6 which I did not put back.
But you had the plunger connected, because you had just clipped that wire in when it fired. So it was connected, even if the connector itself wasn't, and should still have fired successfully in test mode
I used 1 line with a clip at either end. 1 clip was attached to the board pin, the other clip was attached to the probe - so I could test each wire in the connector. I did not remove each wire from the connector. I'm sorry, that was confusing. 
The plunger did fire successfully when tested as I just described.
So position 17 seems the culprit on the board. Replace the transistor (obviously test as well)?
Pretty certain that is Q29, I'll have to check again, but I've identified that bad boy on the board already. Doesn't appear burnt, but I'm certain that doesn't matter.
Any concerns about the connector side?
Again, thank you so much for the time you are spending! If we make it out to Letchworth this summer I'll have to buy you dinner!
Quoted from RonSS:So position 17 seems the culprit on the board. Replace the transistor (obviously test as well)?
Looks like it. With the machine off, you should never get 0 ohms continuity from any driver pin to ground. Since the solenoids are controlled by connecting them to ground, that means one would be on instantly when you turn the machine on.
pin 17 seems to be Q29 looking at the schematics online, which does correspond to the Plunger Kicker from the looks of it. Since that's the case, I'd replace the diode on that coil, and while it's off verify the resistance. Take the board out, test the transistor, if it doesn't read the same as its neighbors, replace it.
While you've got the board out, you should check if anything up the chain may be damaged. While Q29 is out, verify the two resistors that help drive it. They're part of RN5 and RN14, take a look on the schematics to find the right pin numbers, and make sure their resistance is right. Check that the associated capacitor (C63) isn't shorted. You can't test capacitors themselves, but you shouldn't get continuity across it. When in doubt, again compare the resistance of C63 with others.
You can also try to test U29 with the diode test of your DMM. There's a good guide on pinwiki but for some reason they've blocked google so I can't find it. Basically, put one lead on the ground pin (9) and one on each input and output (1 and 18 in this case), and compare with another set of pins (eg 2 and 17). Move the lead from ground to the high voltage pin (10) and try again. Reverse the leads and try again. As always, if something seems way off, you've probably got a bad part.
None of these tests are 100%, and they get less reliable the further in you go, but always worth a shot.
Phew, that's a lot to take in. I'll start with the diode and compare some transistors, replacing as appropriate. Then go back and revisit the other suggestions.
Again, many thanks. Above and beyond.
Quick update:
I removed the diode to the plunger, of course it was fine.
I then removed the circuit board. As guessed, many issues with Q29, C63, and seems like RN14. I just some quick tests with the DMM before desoldering (and lunch - I was starving!). So I guess I'm about to learn how to de/solder circuit boards! I'll find a donor board first to practice a little, and upgrade my soldering tools a touch, the Harbor Freight Solder Iron and Radio Shack bulb sucker may need a little help with this endeavor.
I'll start a new thread if help is needed.
Again, thank you to everyone helping out. Truly learning a lot here!
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Rochester, NY
Sana'a