(Topic ID: 191197)

GTB Sys 3 - switch and lamp strobe out

By arolden

6 years ago


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  • 12 posts
  • 4 Pinsiders participating
  • Latest reply 6 years ago by arolden
  • Topic is favorited by 1 Pinsider

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#1 6 years ago

Hi all,

I am hoping you can give me some Gottlieb System 3 troubleshooting advice. I have a Cue Ball Wizard with switches and lamps not working. After some investigation I determined that the entirety of Strobe 9 is not working.

Now I work mainly with WPC systems so I am not sure how where to go from here. I swapped in a working control board from another System 3 and switches and lamps all start working again. So it is a component issue on the board. However I do not have a manual handy and can’t find a copy of the schematics. Can anyone please advise what components/traces I should be looking at on this board?

Many thanks!

2 weeks later
#2 6 years ago

Bump! Hoping someone can help me out.

I have tested all of the transistors on the driver board. They all test OK. Q45-52 have been replaced with the correct type of transistor (as suggested in Clay's guide). I cannot think of what else to test and I am having trouble following the schematics. Where can I find out which switches are connected to which transistors and ROM? I have the manual and have been studying the driver board schematics but cannot find a way to associate the switches and lamps with the ROMs or connectors.

Any help is appreciated!

#3 6 years ago

I have now tested U1-8, R17-24, and R33-56. All test OK.

Not much on the board left to check and I am struggling to see what other components could be an issue.

#4 6 years ago

I'd have to look at the schematics for connector numbers....but I have had a similar problem before and found a bad diode on the return line. These are the tiny diodes next to the connectors on the driver board.

#5 6 years ago

I checked all of the diodes on the board. All of them give good values around ~0.62.

I have focused on following the circuit from the A3P3 connector, through the transistors, the associated resistors, and then to U8/U9 and then U6/U7. Continuity is good through all of the traces. All resistors are within spec. All transistors test OK. I did notice 1 discrepancy when testing U6. Pins 1 and 2 return values of >0.7 whereas all other pins on other ICs return ~0.6-0.7. This is with the multimeter in diode test, one probe on ground. I don't have a logic probe to confirm these measurements. Is there an issue with this variation?

I'm not sure where to check after U6/U7. Could this be an issue with the SIPs or capacitors? I don't really know how to check these so they are the only unknown.

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#6 6 years ago

I grabbed the driver board out of my Tee'd Off and the same IC gives readings of 0.7. So still a bit high, but this is a working board so higher readings on these pins is obviously normal for this IC. Back to square one for now.

#7 6 years ago

Ok, I'm getting desperate now. Bump for help!

#8 6 years ago

Did you test the diode board underneath the playfield if there is one on cbw?

#9 6 years ago
Quoted from Don44:

Did you test the diode board underneath the playfield if there is one on cbw?

The switches and lamps all work fine when another working driver board is plugged in, so the diode board has been eliminated as a potential issue.

#10 6 years ago

Shared lamp and switch strobes... yuck!

Strobe 9 comes out A3P3 via pin 3. Since the switch matrix is using a shift register (U5 and U7) and LS8 & LS10 work (I assume you checked) then the shift register is working. Narrows things down to only a few things.
U7, Pin 4 -- check him with logic strobe to see if pulsing.
U9, pin 11 -- should be same as U7 pin 4.
U9, pin 12. This one has a pullup to 20V so depending on your specific logic probe, you might not be able to test him with the probe. If you have an O'scope - check for pulses.
Q42 -- I would suspect him first. Can check with o'scope if you have one.

Items involved with Strobe 9:
U6 & U7 - 74HC164 shift registers. U6 works so ignore him. U7 seems to mostly work but you need to verify if output Q1 on pin 4 is active.
U9 - 7406 open collector inverter. Possible his output 6 on pin 12 is bad.
Resistors R54 330 ohm, and R42 1K ohm. Unlikely source of problem but possible.
Transistor - 12P06. The actual driver transistor. MOSFET type transistor and easily damaged. Also - the standard transistor test function does not work properly on MOSFET type transistors, especially in circuit. Often the 0.7V you see is the intrinsic diode within the MOSFET between the drain and source.
Resistor network 10K x 7 (4608x-101-103) - unlikely.
Capacitors C6 and C7 are bypass caps for U6 and U7... don't worry about these two.

#11 6 years ago
Quoted from G-P-E:

Shared lamp and switch strobes... yuck!
Strobe 9 comes out A3P3 via pin 3. Since the switch matrix is using a shift register (U5 and U7) and LS8 & LS10 work (I assume you checked) then the shift register is working. Narrows things down to only a few things.
U7, Pin 4 -- check him with logic strobe to see if pulsing.
U9, pin 11 -- should be same as U7 pin 4.
U9, pin 12. This one has a pullup to 20V so depending on your specific logic probe, you might not be able to test him with the probe. If you have an O'scope - check for pulses.
Q42 -- I would suspect him first. Can check with o'scope if you have one.
Items involved with Strobe 9:
U6 & U7 - 74HC164 shift registers. U6 works so ignore him. U7 seems to mostly work but you need to verify if output Q1 on pin 4 is active.
U9 - 7406 open collector inverter. Possible his output 6 on pin 12 is bad.
Resistors R54 330 ohm, and R42 1K ohm. Unlikely source of problem but possible.
Transistor - 12P06. The actual driver transistor. MOSFET type transistor and easily damaged. Also - the standard transistor test function does not work properly on MOSFET type transistors, especially in circuit. Often the 0.7V you see is the intrinsic diode within the MOSFET between the drain and source.
Resistor network 10K x 7 (4608x-101-103) - unlikely.
Capacitors C6 and C7 are bypass caps for U6 and U7... don't worry about these two.

Thank you so much for the advice!

A couple of things I gather from this. Btw, I made a mistake in my original post - it is not strobe 9 that has the problem, but strobe A. No big issue, I've just looked at the relevant components for strobe A instead of the ones you listed.

Strobe A comes from A3P3 pin 2. I have not checked LS 9 or 11. How do I check these?

Unfortunately I don't have a logic probe. Guess it is time to get one! I take it I will need to look at U7 pin 5, U9 pin 11 and U9 pin 12. You listed U9 pin 11 should be checked for strobe 9 but did you actually mean pin 13?

Is there any effective testing I can do on these ICs with a DMM at all?

Resistors 43 and 55 are both good.

That leaves Q43 as a potential culprit. I didn't know that a standard diode test wouldn't work with these MOSFETs. Interesting. My only experience is with other manufacturers who use transistors. Is there a better way to test it with a DMM? I will replace this one as a first step I think, then look at the ICs with a logic probe.

#12 6 years ago

An update on this issue.

Q43 was indeed the problem. It was testing OK in circuit but bad out of circuit. After charging the gate and then testing the Q43's ON state via ground and source, I was getting no voltage drop when I should have been.

Replaced Q43 and all is working properly.

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