Lamp column out on JD


By arolden

7 months ago


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  • Latest reply 6 months ago by arolden
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PDB U9 test.jpg
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LMP MX row4.jpg
LMP red dot.jpg
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#1 7 months ago

Hi all.

I need some help with diagnosing a lamp issue on JD. All lamps on column 4 are not working. All of these lamps are on the large lamp board in the bottom centre of the playfield. I have checked all of the bulbs are actually working - they are. I have checked all of the diodes and solder joints on the lamp board - all good. Solid 18v is present at TP8. I have checked for continuity from J137-4 in the backbox to each of the lamps - all good. I have also checked the transistor at Q95, which controls this column - all good. I also did the jumpered lamp socket test (between J133 and J137), and all columns lit the test lamp properly.

I'm not sure where to go with the troubleshooting from here. I suspect that I need to start looking at the ICs on the power driver board, but I do not have a logic probe.

Thanks for any help.

#2 7 months ago
Quoted from arolden:

Hi all.
I need some help with diagnosing a lamp issue on JD. All lamps on column 4 are not working. All of these lamps are on the large lamp board in the bottom centre of the playfield. I have checked all of the bulbs are actually working - they are. I have checked all of the diodes and solder joints on the lamp board - all good. Solid 18v is present at TP8. I have checked for continuity from J137-4 in the backbox to each of the lamps - all good. I have also checked the transistor at Q95, which controls this column - all good. I also did the jumpered lamp socket test (between J133 and J137), and all columns lit the test lamp properly.
I'm not sure where to go with the troubleshooting from here. I suspect that I need to start looking at the ICs on the power driver board, but I do not have a logic probe.
Thanks for any help.

Check the connectors again, check the connector pins of the lamp board.

Also reseat the ribbon cable from the CPU to the driver board on both sides.

How did you test the TIP107?

#3 7 months ago
Quoted from arolden:

I also did the jumpered lamp socket test (between J133 and J137), and all columns lit the test lamp properly.

If you did this test properly and the column 4 lamps lit when they were supposed to, you can stop looking at the boards. I love this lamp matrix tester, but the jumpered test can get you the same results with a bit more work.
http://www.siegecraft.us/presta/index.php?id_product=11&controller=product&id_lang=1

The most likely cause of a column not lighting is a broken wire. For columns, you can test DC voltage, and you will normally see something close to 3V (due to the 18V being pulsed). Test it at the connector to start, then test again at the lamp board. From there you can narrow down where the open would be.

#4 7 months ago
Quoted from german-pinball:

Check the connectors again, check the connector pins of the lamp board.
Also reseat the ribbon cable from the CPU to the driver board on both sides.
How did you test the TIP107?

Initially I found a couple of cold solder joints on the lamp board and reflowed some solder onto them. So the lamp board is 100%. I will recheck the connector and the connector on the power board.

I checked the TIP107 two ways. First, I checked for continuity between the tab of the transistor and TP8. There was no continuity. Second, I used diode test to check each of the transistor's legs. They returned similar values to the TIP107 next to it, which was working fine, so I took that to mean the TIP107 was OK.

Quoted from herg:

If you did this test properly and the column 4 lamps lit when they were supposed to, you can stop looking at the boards. I love this lamp matrix tester, but the jumpered test can get you the same results with a bit more work.
http://www.siegecraft.us/presta/index.php?id_product=11&controller=product&id_lang=1
The most likely cause of a column not lighting is a broken wire. For columns, you can test DC voltage, and you will normally see something close to 3V (due to the 18V being pulsed). Test it at the connector to start, then test again at the lamp board. From there you can narrow down where the open would be.

I will check for the 3V and see what I get. However, I know that the wire from J137 to the lamp board is fine. I will check the row return as well while I'm at it.

If I am understanding you correctly, if the socketed lamp test works, then all lamp matrix components on the power driver board should be working 100%. Is that correct?

#5 7 months ago
Quoted from arolden:

... If I am understanding you correctly, if the socketed lamp test works, then all lamp matrix components on the power driver board should be working 100%. Is that correct?

YES, that should be correct.

If a complete column is not working, the problem is not in the return but in the supply area.

Try to press the wires in the Molex connector J137-4.

#6 7 months ago

Aha! I made some progress today.

I redid the socketed lamp test. Turns out I did it incorrectly the first time. Column 4 does not turn on the lamp. I took a video of the process: » YouTube video

So let me know if this thinking is correct: according to the schematic the problem must be the TIP107, ULN2803, LS374 or LS240. I tested the TIP107 and got good readings, as I did last night. I've attached some photos of the tests.

So how do I go about testing the other components? Which is the most likely culprit?

image (resized).jpeg

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#7 7 months ago

I just noticed something strange when testing U18. In diode test, two pins do not return normal values. Looks to me like a short. Could this be the issue?

image (resized).jpeg

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#8 7 months ago

The measurement in 2nd photo (with .032 in display) is indeed Column 4 related.
Problem is that it can be the output of U9-9 (ls240) or the input of U18-18 (ls374)

@ the red dot:
LMP red dot.jpg

#9 7 months ago
Quoted from zaza:

The measurement in 2nd photo (with .032 in display) is indeed Column 4 related.
Problem is that it can be the output of U9-9 (ls240) or the input of U18-18 (ls374)
@ the red dot:

It looks to me like that pin relates to Q96. Or am I not reading the schematic properly? The pin from the first image seems to be related to Q98. Please correct me if I'm wrong.

Regardless, I will check the LS240 chip tomorrow. If it also gives me bad readings, should I replace both of them, or just the LS240?

#10 7 months ago
Quoted from arolden:

It looks to me like that pin relates to Q96.

If I see correct, data 03 = Column 4 = Q95.

I would careful clip the leg of one IC, U18-18 or U9-9 and measure where the short comes from.
LMP MX row4.jpg

#11 7 months ago
Quoted from zaza:

If I see correct, data 03 = Column 4 = Q95.
I would careful clip the leg of one IC, U18-18 or U9-9 and measure where the short comes from.

Hi zaza, sorry, I'm not sure how to verify where the short is coming from once I clip the pins. How should I do this?

#12 7 months ago

If you separate the 2 IC's by clipping one leg (red dot in picture post #8) , then you can verify the same way as you did in post #7 but now on both IC's

#13 7 months ago
Quoted from zaza:

If you separate the 2 IC's by clipping one leg (red dot in picture post #8) , then you can verify the same way as you did in post #7 but now on both IC's

OK, I think I understand. So when one of the legs is clipped, that should isolate the short to just one pin - is that correct?

#14 7 months ago

Yes, this way you can measure if U9-9 has a short or U18-18 is the problem.

#15 7 months ago

Zara, could it be one of the 2 resistors by Q95?

#16 7 months ago
Quoted from kvan99:

could it be one of the 2 resistors by Q95?

Yes, technically Col.4 doesn't work without R185. (R184 is a pull-up)
But arolden has a different (very low) reading on U18 pin18 and that is data for Col.4
When identical inputs/outputs give higher readings, then there is likely something wrong with U9-out or U18-in.

#17 7 months ago
Quoted from zaza:

Yes, this way you can measure if U9-9 has a short or U18-18 is the problem.

OK, understood! I assume it is OK to desolder U18 completely and then test it while out-of-circuit and then test U9 while it is in-circuit? That way I won't damage pins on a potentially good chip.

#18 7 months ago

Yes you can desolder it completely if you have the equipment for it.

#19 7 months ago

If you do desolder it, I would recommend replacing it with a socket and a new chip.

#20 7 months ago
Quoted from zaza:

Yes you can desolder it completely if you have the equipment for it.

Quoted from herg:

If you do desolder it, I would recommend replacing it with a socket and a new chip.

Yep, that is my plan. I just bought a nice soldering station with a desoldering gun so I'm eager to try it out. I will give this a try tomorrow and report back.

#21 7 months ago

I desoldered U18 from the board. Even with a desoldering gun I lifted a few solder pads. How are you supposed to avoid lifting the pads? I could see light through every hole and desoldered for a good length of time on each pin. I made sure as much solder was off as possible. Is lifting some pads off unavoidable when you take an IC out like this? Very frustrating. I know you would normally clip the IC off the pins but I did not want to ruin a good IC.

But now that U18 is out, all of the pins give good readings. Multiple U9 pins give bad readings on both sides of the IC. Does this just mean U9 is bad, or do I need to test further up the chain?

image (resized).jpg

#22 7 months ago
Quoted from arolden:

Is lifting some pads off unavoidable when you take an IC out like this?

Sometimes it will come loose if you wiggle it, but I prefer to ruin an ($1) IC and cut all legs first and desolder one by one.

Quoted from arolden:

Multiple U9 pins give bad readings on both sides of the IC.

Why do you think multiple pins are bad. There was only 1 out of 8 LAMP-Col not working.
Compare the pins with each same segment of the IC.
U9 pin 3,5,7,9,12,14,16,18 are similar (data input) and so are 2,4,6,8,11,13,15,17 (data out)

#23 7 months ago
Quoted from zaza:

Sometimes it will come loose if you wiggle it, but I prefer to ruin an ($1) IC and cut all legs first and desolder one by one.

Why do you think multiple pins are bad. There was only 1 out of 8 LAMP-Col not working.
Compare the pins with each same segment of the IC.
U9 pin 3,5,7,9,12,14,16,18 are similar (data input) and so are 2,4,6,8,11,13,15,17 (data out)

Maybe I'm not testing it properly. I'm testing it the same way I tested U18, in diode test with one probe on ground and the other probe on each other pin. Is that the correct way to do it?

#24 7 months ago

with multimeter set to 'diode' and red pen on GND, test colored legs on U9 with black pen:

PDB U9 test.jpg

Those are the values with my multimeter but it can be different when U18 is out of circuit.

#25 7 months ago

OK, it looks I wasn't measuring properly from ground the first time. I get normal readings on all pins except Q3 which reads 0.32 in diode test. So it looks like U9 is bad to me. What do you think?

image (resized).jpg

#26 7 months ago

That looks indeed the same low value on U9-9 as you measured while U18 was still in circuit.
If all other values were more like the example in post #24 then you found the defective component.

(Black pen on U9-9 = output 'Q3' = data for LampColumn4 )

#27 7 months ago

You have discovered the reason for cutting the chip legs and removing them one by one. Even with the best de-soldering station and experts using it, you can STILL damage tracks.

The chip you are replacing is suspect anyway so why bother trying to save it? They are also less than $1.

I strongly advise cutting the chip legs in future, then use tweezers and remove each I.C. leg and THEN, use your de-solder station to clean out the holes.

#28 7 months ago

I know I'm coming a little late to the party, but I think it's worth mentioning that if you were to invest in a logic probe, you could have hit 4 points on the power driver board (U9-11, U9-9, U18-18, and U18-19) and know exactly what was wrong.

Actually...You would also need to check U19-1 and U19-18 as well, although I would likely not use the logic probe to check U19-18.

#29 7 months ago
Quoted from Homepin:

You have discovered the reason for cutting the chip legs and removing them one by one. Even with the best de-soldering station and experts using it, you can STILL damage tracks.
The chip you are replacing is suspect anyway so why bother trying to save it? They are also less than $1.
I strongly advise cutting the chip legs in future, then use tweezers and remove each I.C. leg and THEN, use your de-solder station to clean out the holes.

Hi Mike,

Absolutely agree. I usually clip the pins and remove the IC first. But this was my first try with a desoldering station; I was confident I could do it cleanly without having to destroy the IC. Turns out I saved the IC and can reuse it like I planned to, but it wasn't worth the damage I caused. I have had good success with just a solder sucker previously. I just thought a desoldering gun might be able to do it in one go. Lesson learned.

Quoted from Pin_Guy:

I know I'm coming a little late to the party, but I think it's worth mentioning that if you were to invest in a logic probe, you could have hit 4 points on the power driver board (U9-11, U9-9, U18-18, and U18-19) and know exactly what was wrong.
Actually...You would also need to check U19-1 and U19-18 as well, although I would likely not use the logic probe to check U19-18.

Good point. However, I only do these kinds of repairs quite rarely so I can't justify the expense. It definitely would have made things easier, though.

#30 7 months ago
Quoted from arolden:

Good point. However, I only do these kinds of repairs quite rarely so I can't justify the expense. It definitely would have made things easier, though.

A logic probe is cheap, and if it saves you having to remove a single IC, the time saved has nearly paid for the probe. I didn't shop around, this is just the first one that popped up:
amazon.com link »

1 week later
#31 6 months ago

I finally got my replacement ICs and installed them into JD yesterday. Success! All lamps now work properly.

Thank you all for the advice.

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