Anyone local have 100 ohm resistor?

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Hilton
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Anyone local have 100 ohm resistor?

Post by Hilton » Mon Sep 11, 2017 6:55 pm

I made a boo boo on my Andromeda and desperately trying to bring it back to life before MRP

brown black brown gold banding if you want to check stock

Would love to grab it tonight or Tuesday if possible

A few would be great as I may F up more when trouble shooting :)
Hilton
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Re: Anyone local have 100 ohm resistor?

Post by Hilton » Mon Sep 11, 2017 9:02 pm

Nevermind
QuyN
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Re: Anyone local have 100 ohm resistor?

Post by QuyN » Tue Sep 12, 2017 8:21 am

Happens to the best of us ;)

But the big question...will it be ready in time?!
Hilton
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Re: Anyone local have 100 ohm resistor?

Post by Hilton » Tue Sep 12, 2017 8:57 am

QuyN wrote:
Tue Sep 12, 2017 8:21 am
Happens to the best of us ;)

But the big question...will it be ready in time?!
sadly, unlikely.

I am going to try but I really F'd things up good.

I located some 100 ohm resistors, but that is just the start. It appears I blew numerous chips and really gorked things up.
Hilton
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Re: Anyone local have 100 ohm resistor?

Post by Hilton » Tue Sep 12, 2017 8:58 am

If anyone local is confident in board work and can help, then please let me know.

I would happily pay good money to get this board fixed locally where it can be tested in the game (seems there are no test rigs for GP MPUs so few people that work on them)

The board was really nice prior to this F up.
Phreezer
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Re: Anyone local have 100 ohm resistor?

Post by Phreezer » Tue Sep 12, 2017 11:18 am

Never seen this game, but in the process of reading about it found your related thread on pinside which helped give some more background info on what happened and what you've looked at so far.

As a disclaimer I've never worked on any Game Plan machines, so not claiming to have any special knowledge about them, but have a lot of experience & equipment related to general board repair and troubleshooting so happy to help get your board running for your charity event if I can.

The advice you've gotten so far on Pinside seems sound, especially given the somewhat limited documentation there seems to be on this game. I did have a couple of follow on questions:

1) Have you gotten the burnt resistor area of the board cleaned up and replaced yet?
2) If so have you already tried powering it back on and were there any signs of life from the board at all (displays working, LED indicators on the PCB flashing, lamp matrix activity, etc.)? You commented that you thought you may have blew multiple chips, so guessing you have reason to believe there is more than just the switch matrix input circuitry damaged.
3) If there are no signs of life, have you checked to make sure your power supplies are still outputting the correct voltages (particularly the +5V supply)?

Assuming that high voltage did get applied to J5-7, the best case scenario would be that the 1N4004 diode between the input and +5V rail clamped the voltage well enough to prevent damage to anything else until the 100ohm resistor had burned itself up. Worst case scenario would be that while current was been shunted into the +5V rail through this protection diode the +5V rail would have gotten pushed up in voltage to a high enough level that it could have damaged any chips powered from that rail (i.e. basically any chip on this board). That can happen because the +5V regulator circuits are usually designed to regulate for circuits that draw power from them, and can't handle large amounts of power being dumped back into the rail as could be the case here. If other chips were damaged you would most likely measure a pretty low resistance between the +5V rail and GND on the PCB when it is unhooked from the wiring harnesses. Most likely the answer is somewhere in between, with the 100ohm resistor, U14, clamp diode, and maybe U17 the things most at risk of being damaged.

I took a quick look at the full sharpshooter schematics to see if the wiring problem on the flipper you found makes sense with the particular input resistor that got burnt and it looks like it does. According to the "GamePlan model 130 playfield.pdf" schematic, Strobe 4 is a white wire and that looks to be the color soldered to the lane change switch you found that was bumping into the EOS switch which would have been at ~24V. The grounds of the +5V and +24V rails get tied together in the power supply board, so it looks like everything was there to generate a ~200mA fault current as shown in the pic below. That more than enough current to burn up that resistor, but luckily shouldn't be enough to have boosted the +5V rail to the point of damaging everything.

Took a look at my stock of 74xxxx parts and don't have any of the 154's unfortunately, when is that part coming in for you?
Attachments
fault.JPG
Hilton
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Re: Anyone local have 100 ohm resistor?

Post by Hilton » Tue Sep 12, 2017 12:04 pm

thanks very much Phreezer.

I am grabbing some 100ohm resistors form a friend locally today so will drop one in tonight.

Any issue/ risk with just replacing that resistor and then powering back on? Just wanted to check.

I started going throgh the board and found 1 diode testing low and a few other resistors that are testing out of spec in other areas of the board.
This is what made me assume there is more wrong than just the initial/obvious fried resistor.

I placed an order for a bunch of varios parts from GPE yesterday so with any luck they will all arrive by late this week or early next.

When I get home from work I can take more photos and denote other components out of spec to help show what I found with my DMM.
Phreezer
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Re: Anyone local have 100 ohm resistor?

Post by Phreezer » Tue Sep 12, 2017 1:22 pm

The risk of powering it back up after removing the wiring problem you found and fixing the resistor should be pretty low. I would use the diode test of the DMM (if your DMM doesn't have that the resistance mode should also work) to check from +5V to GND on the PCB before plugging it back in just to make sure there is nothing obviously shorted. The exact voltage you see with the diode test won't be particularly meaningful since there is a bunch of non-powered circuitry connected to that rail, but if the test reads under a diode drop steady state then it is likely there is another IC damaged somewhere and it would be best to track that down before fully powering it back up.

Assuming you don't see anything like that, the biggest thing to watch for when powering it back up are signs that any of the coils are locked on so you can shut it back off before they stay on long enough to overheat anything.

If you were measuring components in-circuit there is is a good chance that they are probably fine and would measure ok out of circuit, especially if the values you are seeing aren't really close to a short or an open. Most of the time when resistors or diodes are stressed they will fail open or short, so even reading something like 5k across a 20k resistor when it is in-circuit is more likely to be due to other paths through surrounding circuitry than it is from the part itself being out of tolerance. Since pinball boards frequently have many copies of the same circuit (like lamp matrix output drivers for example) you can frequently get a better feel by comparing in-circuit readings from the corresponding part in another copy of the circuit. This usually works best with the wiring harnesses unplugged since there are frequently unused positions in the lamp and switch matrices which can make in-circuit readings asymmetric. If you see something that looks suspicious enough to you and want to rule out in-circuit measurement problems you can desolder one of the leads on the diode / resistor and lift it out of the pad, then redo the measurement across the component leads.

Feel free to let me know if there is anything you want a second opinion on before powering it back up. Would definitely sanity check your +5V supply output with the MPU unhooked if you can too, especially before putting any new ICs on the board that could be damaged by that rail if it is broken. Good news is this looks like a pretty simple MPU design, so hopefully shouldn't be too many rocks to turn over in reviving it.
Hilton
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Re: Anyone local have 100 ohm resistor?

Post by Hilton » Tue Sep 12, 2017 1:41 pm

thanks Phreezer.

I was testing stuff with the board removed and running down each row of diode and resistors to check that they tested out similar to each other.

I was finding things like in a row of 1k resistors that 1 of them was showing 673 instead of 1k
I found a diode testing in diode mode at 4.5ish rather than 5.o like the others.

This made me assume they were also bad. but I tried to physucally trace back the traces on the board and could not figure out how some of the potentially faulty stuff would have been in line with the pin I shorted through the high voltage.


Curious, where are you located? Any chance I could pay you to sing over some night early next week to diagnose with me?
I can of course do it all online but in person is always quicker and I learn more. I am still a novice at board diagnosing so I have lots of stupid questions and lack of confidnce on what to test/where/how without screwing something else up furhter.

I can desolder and solder well enough, but the diagnosing is my weakness.
QuyN
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Re: Anyone local have 100 ohm resistor?

Post by QuyN » Tue Sep 12, 2017 1:42 pm

Bummer man. Saw your thread on pinside (thanks Phreezer), but you'll get it sorted out ;) Wish I could help and it sounds like you've got some good knowledgeable people already on the case. Can't wait until it's up and running!
Phreezer
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Re: Anyone local have 100 ohm resistor?

Post by Phreezer » Tue Sep 12, 2017 5:00 pm

Hilton wrote:
Tue Sep 12, 2017 1:41 pm
thanks Phreezer.

I was testing stuff with the board removed and running down each row of diode and resistors to check that they tested out similar to each other.

I was finding things like in a row of 1k resistors that 1 of them was showing 673 instead of 1k
I found a diode testing in diode mode at 4.5ish rather than 5.o like the others.

This made me assume they were also bad. but I tried to physucally trace back the traces on the board and could not figure out how some of the potentially faulty stuff would have been in line with the pin I shorted through the high voltage.


Curious, where are you located? Any chance I could pay you to sing over some night early next week to diagnose with me?
I can of course do it all online but in person is always quicker and I learn more. I am still a novice at board diagnosing so I have lots of stupid questions and lack of confidnce on what to test/where/how without screwing something else up furhter.

I can desolder and solder well enough, but the diagnosing is my weakness.
Sure I can come by and lend a hand, sounds like you have already been following a good approach so far (comparing readings to similar sections & trying to trace back outliers to see if it makes sense that they could have been impacted by the fault you know about), so that's a great start. I'll send you a PM to make sure you've got my contact info and we can figure out a time that works.
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