(Topic ID: 295142)

NBAFB F106 blows immediately

By curban

4 months ago


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  • Latest reply 3 months ago by curban
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#1 4 months ago

F106 is now blowing immediately on power up of my NBAFB. Manual says it’s the +18V Lamp Matrix. After the first time it blew, I replaced and could play for a minute before it blew again. Now it blows immediately when I turn on the power.

I tried disconnecting J125 and J121 which are the row and column connectors for lamp matrix, but the fuse still blows immediately on power up.

Looking for suggestions to troubleshoot.

#4 4 months ago

Embarrassing, but I don’t know how to test this with my DMM

Touched one lead to right side of fuse holder and other lead to ground. And that somehow turned the volume of the pin to max.

#5 4 months ago

Should I test between TP102 and ground?

#6 4 months ago

LED100, 102,and 104 are out.

#7 4 months ago
Quoted from curban:

I don’t know how to test this with my DMM

No worries! We all start somewhere.

The link I posted has this video that walks you through it:

#8 4 months ago

Getting 1.32 at TP100 12VDC Regulated
5.07 at TP101 5VDC digital
0.00 at TP102 18VDC lamps
13.1 at TP103 12VDC unregulated
23.3 at TP104 20VDC flash lamps

This is with the blown fuse in

#9 4 months ago

Were you doing any kind of work to it lately? Changing bulbs or anything at all? Try testing BR1.

#10 4 months ago

Test diode D11-D12-D13-D14

#11 4 months ago
Quoted from Karetaker:

Were you doing any kind of work to it lately? Changing bulbs or anything at all? Try testing BR1.

Unfortunately, there is not a BR1 on the WPC95 driver board that is in NBAFB.

#12 4 months ago
Quoted from zaza:

Test diode D11-D12-D13-D14

Diode test these that zaza mentions.

#13 4 months ago

I pulled each of D11-D14 from the board and tested and they all seem to be fine.

For what it’s worth, when I try testing the diodes in place, D7-9 and D11-14 all show ‘flow’ in both directions…but I believe that’s why you have to pull to test.

#14 4 months ago
Quoted from Karetaker:

Were you doing any kind of work to it lately? Changing bulbs or anything at all?

I hadn't done anything to the machine but play it for quite a while before F106 blew the first time.

I'm afraid I worsened things when I first attempted to measure the voltage by doing this: "Touched one lead to right side of fuse holder and other lead to ground.".

#15 4 months ago
Quoted from curban:

I pulled each of D11-D14 from the board and tested and they all seem to be fine.
For what it’s worth, when I try testing the diodes in place, D7-9 and D11-14 all show ‘flow’ in both directions…but I believe that’s why you have to pull to test.

These in this particular part of the board can be tested on the board. Normally, if it needs to be pulled, someone will remind you to do it. A diode on a coil definitely is a time when the diode needs to be removed to test the diode.

What are the results measured on the diode test? Were they all within. 4 to .6 volts?

On some meters, you have to press select in order for the diode symbol to be displayed on the screen. Meter was set up that way?

Did you put the red meter lead on the non-banded side of each of the diodes and black lead on the banded side when doing this diode test?

#16 4 months ago

When black is on banded side, meter reads between 460-490. (First photo is D11)

When red is on banded side, meter always reads 1 (second photo is D11)

I know you didn’t tell me to check D7 and D8, but these are showing ~1270 when red is on banded side. (3rd photo is D8)

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#17 4 months ago
Quoted from curban:

I hadn't done anything to the machine but play it for quite a while before F106 blew the first time.
I'm afraid I worsened things when I first attempted to measure the voltage by doing this: "Touched one lead to right side of fuse holder and other lead to ground.".

What probably happened is that your meter wasn't set to the correct measurement mode when you touched the fuse holder and the ground. It might have been set to measure resistance / continuity and then when you placed the probes, the meter kinda shorted the power lines through the resistance measuring circuit , hence the weird effect of maxing out the volume. It is unlikely that you damaged the board this way. There were more chances of actually breaking your DMM or the main fuse of the transformer than your boards.

If you post a picture of your multimeter we can guide you as to how you set the meter before taking a measurement. There are 4 types of measurement you need to understand.

AC voltage (wavy line on your meter, VAC)
DC voltage (One straight and one dotted one, VDC)
resistance / continuity (measured in ohms, the omega symbol, continuity often has a speaker symbol and beeps when it measures a low resistance)
diode test (often is the 2nd function of the continuity test its symbol is a line with an arrow inside)

If you mix AC and DC on you meter while trying to measure voltage you will simply measure nothing. So if you are unsure that you are supposed to be measuring AC or DC, trying measuring both types of voltage.

Continuity/resistance is used to measure shorts and coils. It is on the same function as diode. A continuity test will give you a value in ohms while the diode test will give you a value in volts. A short circuit in diode test will give you 0v. A typical diode will read .3 to .7 volts depending on its type. Polarity just be observed on a diode and the black probe must match the side with the band.

The circuit is actually very simple and you should be able to pinpoint the problem fast enough.

The very first test is to place your DMM on AC volts (wavy line), pull out F106 , measure the voltage between J129 pins 6 or 7 and 4 or 5. It should be around 16 VAC. This is probably still normal , but it is the first thing to check.

Removing the diodes to test them should not have been necessary, not in this circuit, especially if F106 is out.

On the picture below, you can measure each diode, in circuit using the diode test on your DMM (line with an arrow inside) by applying the probes to :

D12 -> Red : A (Ground) Black : B (One side of the fuse holder)
D11 -> Red : A (Ground) Black : D (Pins 4 or 5 of J129)
D14 -> Red : B (One side of the fuse holder) Black : C (TP102)
D13 -> Red : D (Pins 4 or 5 of J129) Black : C (TP102)

You say the diodes tested good when pulled, but all showed flow when tested in circuit. Was this with a good F106 fuse ? Most probably. If they all showed flow, this means TP102 and ground are shorted together.

Place the meter in continuity and measure between TP102 and ground this should NOT give you 0 ohms. If this is indeed short (most likely) and the diodes tested good (.3 to .7 volts typically), then either C12 , C11 , R6 + LED102 , C7, Q2 (3 pin 12 volt regulator LM7812),C5 or C40 are shorted. Out of all these , the most likely culprit would be the LM7812. There should not be any continuity between any of the 3 pins of the regulator. (pins 1-2, 2-3, 1-3). It can be easily pulled out but there should not be any shorts in both cases, in or out of the circuit.

This circuit is the reason why you are missing both the 18v and 12v from TP102 and TP100. Did F101 burn ? Is this fuse the correct value ? The manual says it's a 0.63A fuse. Unless this fuse is the wrong one and it much higher in value , I don't think the problem is beyond that fuse.

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#18 4 months ago

The one direction with the red lead on the non banded side and black lead on the banded side is the most important measurement when the diode is in the circuit/board. Sorry that the video did not really cover that part of it. It was more about theory, in that case.

Since F106 is blowing, we were expecting a shorted diode, which would be zero volts on the diode test.

It would not hurt testing all those big diodes in the one direction. It at least will give you more familiarity with the diode test.

I see that you have many or all the connectors unplugged during those measurements. So if the diodes are .4 to .6volts, then it would seem something in the playfield might be the cause.

#19 4 months ago

Your D11 results are normal , on one side it measures 482 millivolts , or 0.482 V, and on the other infinity (1). The diode should not conduct in reverse and especially not read 0 which is a short circuit, and it doesn't when you try to reverse the probes.

Don't compare with D8 , because you are actually reversing the probes when it measures 1.276 Volts. If you look at the circuit , you can see that you actually end up measuring a lot more that just that single diode in reverse when you reverse the probes on D8.

The important thing when measuring a diode is to measure the voltage drop on it , by respecting the probe orientation (the .3 to .7) and that you don't measure a short or open circuit (nothing at all when respecting the orientation). When you see weird results like your reverse D8, the absolute test is to remove it. If you have access to the schematic then you can look and try and figure out why you have those results.

(In your D8 case , by reversing the probes you placed the negative on the ground of the whole board and since the return path for the measurement will always be the shortest path , if the diode was shorted , you'd measure a short, but you won't if it isn't and the current flows through other parts to return to your meter (through other diodes , resistors and maybe even op-amp as in the picture, which ever is the shortest path for the current).

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#20 4 months ago
Quoted from Roamin:

The very first test is to place your DMM on AC volts (wavy line), pull out F106 , measure the voltage between J129 pins 6 or 7 and 4 or 5. It should be around 16 VAC. This is probably still normal , but it is the first thing to check.

Very confused. How do I have it hooked up wrong? Getting a reading of 0.00. When I plug in the connector to J129, playfield lights and defender motor starts to operate fine.

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#21 4 months ago
Quoted from Roamin:

Place the meter in continuity and measure between TP102 and ground this should NOT give you 0 ohms. If this is indeed short (most likely) and the diodes tested good (.3 to .7 volts typically), then either C12 , C11 , R6 + LED102 , C7, Q2 (3 pin 12 volt regulator LM7812),C5 or C40 are shorted. Out of all these , the most likely culprit would be the LM7812. There should not be any continuity between any of the 3 pins of the regulator. (pins 1-2, 2-3, 1-3). It can be easily pulled out but there should not be any shorts in both cases, in or out of the circuit.

With power off shows 1.3 ohm. With power on shows about 6ohm.

#22 4 months ago

Oops, it seemed obvious.. You are measuring for AC, on the board, with the connector disconnected.. But we are interested to know if the connector you removed, brings the correct voltage to the board. You're supposed to measure the connector itself, not the pins on the board when you are checking if the 16v comes in.

#23 4 months ago

Apologize that I’m not answering in order:

F101 is good and it is labeled as 630mA.

#24 4 months ago

You want to measure those 2 blue wires.

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#25 4 months ago
Quoted from Roamin:

Oops, it seemed obvious.. You are measuring for AC, on the board, with the connector disconnected.. But we are interested to know if the connector you removed, brings the correct voltage to the board. You're supposed to measure the connector itself, not the pins on the board when you are checking if the 16v comes in.

Getting 14.4V between connector pin 4 and 7

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#26 4 months ago
Quoted from curban:

With power off shows 1.3 ohm. With power on shows about 6ohm.

Did you measure 1.3 ohm with the lamp connectors disconnected from the board? Either way, 1.3 ohm is way too low. You should NEVER measure resistance/continuity in a circuit while power is on, you risk damaging your meter and the board. Aynways , 18v in 1.3 ohms would equal over 13 amps.. 1.3 amps in your case is probably the probe resistance and / or the connections you made while probing. The real result is probably even less , making the current even more.

There is an issue here for sure. Go back to my first picture and measure continuity between H (one side of F101) and ground. Is this side shorted as well ? Can you remove Q2 and measure continuity again on TP102 and ground ?

#27 4 months ago
Quoted from curban:

Getting 14.4V between connector pin 4 and 7
[quoted image]

That part is fine. 14.4 VAC is about 20.3 VDC and with the rectification of the voltage , it comes even closer to 18 VDC.

#28 4 months ago
Quoted from Roamin:

ou say the diodes tested good when pulled, but all showed flow when tested in circuit. Was this with a good F106 fuse ? Most probably. If they all showed flow, this means TP102 and ground are shorted together.

When I test D11-14 with burnt fuse or no fuse while they’re installed on the board and all connectors are plugged into the board, I get readings of 460-490 regardless of which lead is on the banded side of diode. If I unplug connectors J121-J126, then I get a reading of “1” when I put the red on the banded side. This is with the pinball machine turned off.

#29 4 months ago
Quoted from Roamin:

You should NEVER measure resistance/continuity in a circuit while power is on, you risk damaging your meter and the board.

Thank you.

Quoted from Roamin:

Go back to my first picture and measure continuity between H (one side of F101) and ground

With all connectors plugged in. Power off. I’m measuring 34ohm resistance between f101 and ground tp107.

#30 4 months ago
Quoted from curban:

When I test D11-14 with burnt fuse or no fuse while they’re installed on the board and all connectors are plugged into the board, I get readings of 460-490 regardless of which lead is on the banded side of diode. If I unplug connectors J121-J126, then I get a reading of “1” when I put the red on the banded side. This is with the pinball machine turned off.

Just to confirm, you did desolder all 4 diodes , tried the diode test on them and they all tested fine, correct ? You should check the regulator next. Keep J121-126 disconnected for now. With everything disconnected , resistance between TP102 and ground really shouldn't be 1.3 ohms. Time to test the regulator (LM7812).

#31 4 months ago
Quoted from curban:

Thank you.

With all connectors plugged in. Power off. I’m measuring 34ohm resistance between f101 and ground tp107.

Ok, this should indicate that the short isn't after the LM7812. Looks like Pins 1 and 2 are shorted , but not 2 and 3.

#32 4 months ago
Quoted from Roamin:

Can you remove Q2 and measure continuity again on TP102 and ground ?

This looks pretty difficult to get to. Is that the next step? I dont think I can remove it with the board in place.

#33 4 months ago

Will resume looking at it this evening.

#34 4 months ago

Do you have any tools at all for desoldering? You're not supposed to remove any components without first removing the board from the cabinet. How did you pull out the diodes? Did you just heat them up and pull on them from the component side? With the proper tool, a desoldering pump, you can get that part out in under a minute when the board is removed and you are working on the solder side..

If you pulled on the diode without being careful, you might have damaged the "via". That's the connection between both sides of the board that every hole has. It is easy to damage when you do just that, pull on a leg of a component.

You shouldn't learn to work on boards with an iron, in a board that is precious and has value. If you don't have the skills yet and you really want / like to learn, find some scrap boards and remove components and solder them back to get used to it and not damage the traces and the solder pads/vias.

There aren't really any other steps. If the diodes are good and the lamps aren't connected and tp102 and ground give you 1.3 ohm, you can only test Q2. Testing it out of circuit will easily confirm it was the first (and hopefully) only issue which caused f106 to blow.

#35 4 months ago
Quoted from Roamin:

Do you have any tools at all for desoldering?

Only one of those squeeze bulb suckers.

Quoted from Roamin:

Did you just heat them up and pull on them from the component side?

Yup

Quoted from Roamin:

If you pulled on the diode without being careful, you might have damaged the "via".

Oh-oh.

Quoted from Roamin:

f the diodes are good and the lamps aren't connected and tp102 and ground give you 1.3 ohm, you can only test Q2.

When I got 1.3ohm, the lamps were connected. I apologize if I did this wrong earlier. Specifically, if J122 is connected, I get continuity with very small resistance between TP102 and TP107 (ground). If J122 is disconnected, I get no continuity (resistance maxes out).

#36 4 months ago
Quoted from curban:

Only one of those squeeze bulb suckers.

Yup

Oh-oh.

When I got 1.3ohm, the lamps were connected. I apologize if I did this wrong earlier. Specifically, if J122 is connected, I get continuity with very small resistance between TP102 and TP107 (ground). If J122 is disconnected, I get no continuity (resistance maxes out).

OK, then we are getting closer. So without j122, you get no continuity, which is what we need. I looked up j122 and it does connect to the lamp matrix, and brings column 8 to the coin door board. It is connected to the start button lamp. In your first post you mentionned disconnecting j125 and j121, but we missed that j122 is also in the circuit.

With j122 disconnected, does the fuse still blow? It probably won't.

Check around the start button lamp, anything touching the casing anywhere?

#37 4 months ago
Quoted from Roamin:

With j122 disconnected, does the fuse still blow? It probably won't.

This is encouraging. With J122 unplugged and a new fuse in F106, I was able to play two balls without problem. I don't have time to investigate further until tonight, but I will resume troubleshooting then and report.

This is also the first time that I've been able to turn the volume back down from max!

#38 4 months ago

I think the wires connecting to the lockbar "Shoot" button lamp may have been shorting on the lockbar holder. There was a tiny bit of exposed wire beyond the rubber connector covers and the fit in that area is very tight.

I played a game without J122 connected at all without any problem.
I then played a game with J122 connected but the lockbar button disconnected without a problem.
I then fixed the wires as best I could on the lockbar button and reconnected. Played a couple of balls without problem.

I believe if one of the lamp wires touched the lockbar holder and the lockbar holder was properly grounded this would cause a ground short? Corrrect?

#39 4 months ago
Quoted from PinballManiac40:

Unfortunately, there is not a BR1 on the WPC95 driver board that is in NBAFB.

My bad I didn't realize this was a 95.

#40 4 months ago
Quoted from curban:

I think the wires connecting to the lockbar "Shoot" button lamp may have been shorting on the lockbar holder. There was a tiny bit of exposed wire beyond the rubber connector covers and the fit in that area is very tight.
I played a game without J122 connected at all without any problem.
I then played a game with J122 connected but the lockbar button disconnected without a problem.
I then fixed the wires as best I could on the lockbar button and reconnected. Played a couple of balls without problem.
I believe if one of the lamp wires touched the lockbar holder and the lockbar holder was properly grounded this would cause a ground short? Corrrect?

Yes, definitely the lockbar is grounded by the chassis of the machine otherwise it would present a danger for shock if something shorts inside. Glad for you it was an easy fix.

3 weeks later
#41 3 months ago

This was definitely the lockbar switch shorting on the lockbar. I put heat shrink over each of the four wires to the button and haven't had an issue since.

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