(Topic ID: 305614)

T2 “Ground Short- Rows 2-7” at Start Up

By tharjus

6 months ago


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Topic Stats

  • 26 posts
  • 8 Pinsiders participating
  • Latest reply 52 days ago by Bohm
  • Topic is favorited by 1 Pinsider

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78326F14-013E-49D1-9C4E-877F915122F0 (resized).jpeg
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t2_switch_matrix (resized).png
WPC-089MPULayout (resized).jpg

#1 6 months ago

Hello,
New problem, I just resolved drop target issue. Works great, realized I left flashlight inside. Opened playfield, retrieved light, closed up, now I have new issue.
When machine first starts new error message. “Ground Short- Rows 2-7” . Any idea what I may have touched to cause this error?
Thanks
To

#2 6 months ago

Coil wire to GI lights ? High power to low power can do damage there and other areas.

Unplug ROW 2-7 connectors from CPU and turn game on. If same error you hurt your CPU.

LTG : )

#3 6 months ago

Ok, I’ll take the hit if I caused it, but game was working after all closed up. Stopped working after I reopened playfield to retrieve light. Now I’m gun shy, when you say unplug row 2-7 connectors from cpu, do you mean disconnect jumper 209? Sorry to be a pain, but I do appreciate the help.

#4 6 months ago
Quoted from tharjus:

Ok, I’ll take the hit if I caused it, but game was working after all closed up. Stopped working after I reopened playfield to retrieve light. Now I’m gun shy, when you say unplug row 2-7 connectors from cpu, do you mean disconnect jumper 209? Sorry to be a pain, but I do appreciate the help.

Yes J209 is correct.

#5 6 months ago

Unfortunately that didn’t help.

#6 6 months ago

Based on the picture, I say Chip U18 is blown

WPC-089MPULayout (resized).jpg

#7 6 months ago

Thank you for the input. Assume that I am an amateur (yes I am the first part of the leading word), how do you know whether it’s chip U18 or U19? Is it as easy as it seems to pull the existing chip and replace it with new one, given the old isn’t corroded in place? I’m going to order its replacement now.
Thanks again for the help.
Tom

#8 6 months ago

Be SUPER careful when soldering on the board. The tracks are VERY fine and 30+ year old PCBs are not as good as modern ones - it is so easy to lift tracks you won't believe it.

#9 6 months ago
Quoted from tharjus:

Is it as easy as it seems to pull the existing chip and replace it with new one,

You ever do board work ? If not get help. If so it is U18, LM339's are cheap. Install a socket so if it ever happens again it is an easier fix.

LTG : )

#10 6 months ago

Thank you for heads up, I didn’t look close enough to see it’s soldered I place, I was hoping it could be pulled and replaced. This is why this site is so good.

#11 6 months ago
Quoted from tharjus:

Thank you for the input. Assume that I am an amateur (yes I am the first part of the leading word), how do you know whether it’s chip U18 or U19? Is it as easy as it seems to pull the existing chip and replace it with new one, given the old isn’t corroded in place? I’m going to order its replacement now.
Thanks again for the help.
Tom

U18 is 1st chip tied to row 2-7

#12 6 months ago

Before I cause any further damage, i took your advice and called in the big guns for assistance.
Thanks for everyone’s input.

4 months later
#13 68 days ago
Quoted from tharjus:

Before I cause any further damage, i took your advice and called in the big guns for assistance.
Thanks for everyone’s input.

Did you find a resolution? I'm experiencing the exact same thing with a brand new PCB after doing an LED swap (powered on)

#14 68 days ago
Quoted from Bohm:

Did you find a resolution? I'm experiencing the exact same thing with a brand new PCB after doing an LED swap (powered on)

It is almost a certainty that U20 was damaged.
It is an ULN2803.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#15 68 days ago
Quoted from ChrisHibler:

It is almost a certainty that U20 was damaged.
It is an ULN2803.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Appreciate it, they're cheap enough to just order new ones and try out (hopefully this works on my BSD too) but maybe I can try and diagnose it first.

I'm pretty new to the hobby and finally have a place to start going through the machines I've been collecting for 2 years, T2 is a mess.

#16 68 days ago
Quoted from Bohm:

they're cheap enough to just order new ones

Sockets for them too if you need it. I wouldn't solder the IC's on. And then they'd be easy to replace next time.

LTG : )

#17 68 days ago

Procure a logic probe.
Elenco LP-560 can be had on Amazon for less than $20.
It will be very useful to you.
Here's a quick test with logic probe to see if the columns are strobing correctly.
https://www.pinwiki.com/wiki/index.php/Williams_WPC#Quick_Switch_Column_Strobe_Testing
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

1 week later
#18 55 days ago
Quoted from ChrisHibler:

It is almost a certainty that U20 was damaged.
It is an ULN2803.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Replaced U20 and it un-bricked my switch matrix, but now none of the switches in column 3 will register. I replaced all the connectors to make sure I had good contacts

t2_switch_matrix (resized).png

Also, targets 1-4 in column 7 simultaneously activate the corresponding switches in column 1 but not vice-versa, but that was an issue before I shorted the new cpu board

I did purchase the logic probe but unsure of how to power/use it, can I simply remove all connections from the CPU save from the power driver board, turn on the machine and attach as shown in your link?

#19 55 days ago
Quoted from Bohm:

Replaced U20 and it un-bricked my switch matrix, but now none of the switches in column 3 will register. I replaced all the connectors to make sure I had good contacts
[quoted image]
Also, targets 1-4 in column 7 simultaneously activate the corresponding switches in column 1 but not vice-versa, but that was an issue before I shorted the new cpu board
I did purchase the logic probe but unsure of how to power/use it, can I simply remove all connections from the CPU save from the power driver board, turn on the machine and attach as shown in your link?

Have you tested the associated resistors and caps below U20?

Screenshot_20220506-162411_Chrome (resized).jpg
#20 55 days ago

Sounds like you broke a trace to column 3 changing U20.

#21 55 days ago
Quoted from PinballManiac40:

Sounds like you broke a trace to column 3 changing U20.

Good possibility too, get out the meter and test for continuity.

#22 55 days ago

Black probe power clip onto negative lead of C31, the filter cap adjacent to J210.
Red probe power clip on positive lead of C31.
Power on.
Touch the end of your probe. red/green lights on probe should react and perhaps an audible buzz.
Probe pins 11-18 of U20.
Each pin should be pulsing.

If not, probe pins 1-8. Any pin not pulsing will have a broken trace between U20 and the supplying chip.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

pasted_image (resized).png
#23 55 days ago
Quoted from eyeamred2u:

Have you tested the associated resistors and caps below U20?
[quoted image]

Quoted from PinballManiac40:

Sounds like you broke a trace to column 3 changing U20.

Quoted from ChrisHibler:

Black probe power clip onto negative lead of C31, the filter cap adjacent to J210.
Red probe power clip on positive lead of C31.
Power on.
Touch the end of your probe. red/green lights on probe should react and perhaps an audible buzz.
Probe pins 11-18 of U20.
Each pin should be pulsing.
If not, probe pins 1-8. Any pin not pulsing will have a broken trace between U20 and the supplying chip.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info[quoted image]

Alright, will do, thanks for pointing me in the right direction.

#24 52 days ago
Quoted from ChrisHibler:

Black probe power clip onto negative lead of C31, the filter cap adjacent to J210.
Red probe power clip on positive lead of C31.
Power on.
Touch the end of your probe. red/green lights on probe should react and perhaps an audible buzz.
Probe pins 11-18 of U20.
Each pin should be pulsing.
If not, probe pins 1-8. Any pin not pulsing will have a broken trace between U20 and the supplying chip.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info[quoted image]

Positions 11 & 16 on the output, 3 & 8 on the input did not pulse.
J206/207 position 3, no pulse.

Pulled the board off to inspect and found this:
78326F14-013E-49D1-9C4E-877F915122F0 (resized).jpeg

Looks like a possible errant bridge between Resistors 70 & 71, kind of hard to tell, but the resistance on both checks out. Continuity from J206/207 to U20 then from U20 to U14 also checks out which leads me to believe that maybe I fried U14 too, so I checked it with my DMM and it looks like position 5 has a short, which correlates with no pulse positions on U20 and J206/207. So I’ll get to replacing it as well and cross my fingers

#25 52 days ago

The solder bridge is inconsequential since it bridges leads that are already connected via the trace.
U14 is often damaged in addition to U20.
Is that an OEM board of aftermarket?
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#26 52 days ago
Quoted from ChrisHibler:

The solder bridge is inconsequential since it bridges leads that are already connected via the trace.
U14 is often damaged in addition to U20.
Is that an OEM board of aftermarket?
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Aftermarket, this one:
https://www.marcospecialties.com/pinball-parts/A-12742-XXXXX

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