Whirlwind
Williams, 1990I have a couple of insert bulbs that I noticed were burning out quickly and very bright. I checked the voltage last night on them and they are 12 volts +. Some of the other lamps are more like 4 volts. The two that are at 12 + volts are on the same column. Either they are incorrectly wired or I have a wire touching that circuit that shouldn't be.
Does the GI circuit run at 12 volts?
Quoted from Dewey68:Does the GI circuit run at 12 volts?
The GI circuit is 6 VAC.
Normally if you are reading a high voltage on a column the signal is staying high rather than being pulsed. Although 4 volts sounds way too low for the pulsed signal. Are you using a decent meter?
Check all of the column drives and see how each one reads. If one is high then there's a problem with the board.
Quoted from terryb:Are you using a decent meter?
For testing the columns, I'm assuming run one probe to the pin, the other to ground while running the "all lamps" test? If only someone had a website where you could look this stuff up.... 
Quoted from Dewey68:If only someone had a website where you could look this stuff up....
Easiest thing to do is disconnect the lamp column connector and then check each of the column pins. Since the signal is pulsed you should get about 12 volts. If any of the columns read at 17 volts then that column is locked on rather than pulsing.
Quoted from Dewey68:For testing the columns, I'm assuming run one probe to the pin, the other to ground
Yes.
Quoted from terryb:http://pinballrehab.com/1-articles/solid-state-repair/repair-guides/148-lamp-matrix-theory-and-troubleshooting
Easiest thing to do is disconnect the lamp column connector and then check each of the column pins. Since the signal is pulsed you should get about 12 volts. If any of the columns read at 17 volts then that column is locked on rather than pulsing.Yes.
Thanks Terry for the guidance, and for the website. 
I'll report back with my findings.
Quoted from Dewey68:Okay, as expected, IJ7-8 reads at 16.8 volts. Checking the other pins though, I've got readings from 8 to 4 volts on different pins.
I would guess that's just the quality of the meter. Even expensive meters have difficulty with pulsed circuits since that isn't that they're designed for.
Start making your way back up the circuit until the column in question matches the other columns. If you have a logic probe that works even better since you can see the pulses.
I think system 11's have a resistor pack that pulls up the columns. If so, give it a squeeze and if it crumbles then that's your issue.
The part of the board I need to troubleshoot looks to be this area, correct? I can see how a bad transistor could lock a column on, but I'm struggling with the logic of how different columns can have such different voltages? It looks like the U53 transistors drive the beginning of the circuit, but what's the purpose of the rest of the circuit?
Quoted from Dewey68:but I'm struggling with the logic of how different columns can have such different voltages?
I doubt if they do, it's just a cheap meter.
U52 provides the pulsed signal (5 volts) which needs to be raised to 18 volts and handle higher current. That is the purpose of the two transistors. Same signal across the circuit, just at a higher voltage/current level.
Take readings at the red circles, and you can compare that to the blue circles.
Terry, I really appreciate your patience and help here. I've found the area of the board with the components from the schematic, but I'm not sure where to put the lead when testing. It looks like R82 and R83 I put the lead on the end of the resistor closest to Q52 and Q53, but SR17 and SR18 I'm lost on which end of those to test. Also what pins for U52 and U53?
I'll try to read more on your website as I'm sure the answers are there.
The best way to see the traces on the board is to backlight it and then you can see the traces on both sides. This isn't always feasible so use your meter set on diode/continuity to figure out which points connect.
On the SR's the dash number is the pin number, so SR-9 is pin 9. Pin 1 should have a dot on it.
We'll do the red circles. The one on the right will be on SR16 pin 9 (this should directly connect to R83). The middle red circle can be checked at U52 pin 11. The left circle can be tested at U52 pin 12.
Here's some info on reading schematics.
And the entire series (the better choice, but a lot of reading).
http://pinballrehab.com/1-articles/solid-state-repair/tutorials/147-solid-state-pinball-tutorials
Where's zaza and his wonderful graphics when you need him?
I will try and make this simple for you....
Logic probe U52 PIN 11.
If it is pulsing. Replace q53 and/or q54
If it is not pulsing. Logic probe U52 Pin 12
If U52 pin 12 is pulsing, Replace U52
If U52 pin 12 is not pulsing replace the lamp PIA (middle one)
Quoted from barakandl:I will try and make this simple for you....
Simple is good. Funny thing is I was reading Terry's website on schematics when I checked back here and found the new posts. Thanks to all for the help. If I keep plugging away hopefully I'll be able to follow the logic behind what's going on instead of being spoon-fed. 
Your picture has marked the correct pins discussed above.
I think that Q54 has a solder ball squeezing out of the top of it. Pretty damn good sign that q54 is bad.
Thanks zaza.
Quoted from barakandl:I think that Q54 has a solder ball squeezing out of the top of it. Pretty damn good sign that q54 is bad.
Man you kids have good eyes.
haha i am vibrant 32! I always try and do a really good visual check. I find so much that way. I guess you have to know what to look for, but a lot of it is pretty obvious once you spot it.
i blew it up. could just be the picture, but looks like the telltale sign of an overheated transistor with solder balling up out of the package.
Quoted from barakandl:haha i am vibrant 32! I always try and do a really good visual check.
I was a vibrant 50, now I'm a less than vibrant 61!
I agree 100% on the visual inspection--you can find a lot of problems that way. The most troublesome for me is photographs for some reason.
Quoted from barakandl:I think that Q54 has a solder ball squeezing out of the top of it. Pretty damn good sign that q54 is bad.
Quoted from barakandl:i blew it up. could just be the picture, but looks like the telltale sign of an overheated transistor with solder balling up out of the package.
Ding Ding Ding! We have a winnah! Initial testing with my DMM does show that Q54 is bad, and yes, you saw exactly what you thought you saw, solder coming out of the casing. After dinner I'm going to find the 18 volt power source and try my hand at the logic probe, just for the heck of it. IMG_1745.JPG So is this portion of the circuit acting like a relay, and the relay is stuck on sending too much power to the sockets? I'm still working on the logic of this circuit.
You guys are goooooood!
Quoted from Dewey68:So is this portion of the circuit acting like a relay, and the relay is stuck on sending too much power to the sockets? I'm still working on the logic of this circuit.
Basically yes. The input to the transistor is pulsed (lo and hi) and the output should be pulsed. Instead the transistor is shorted and sending constant voltage to the lamps.
Good catch barakandl.
After replacing Q54 everything is working properly. I now realize that previously when I started up the game all of the lights on that column would be on until the game finished booting. 
Thanks again to everyone who helped me with this issue.
Quoted from barakandl:I think that Q54 has a solder ball squeezing out of the top of it.
holy crap! that's a good find!!
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Plainfield, IL
