(Topic ID: 189449)

NASCAR Fuse Blowing

By Ramtuathal

6 years ago


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  • 16 posts
  • 5 Pinsiders participating
  • Latest reply 6 years ago by pintechev
  • Topic is favorited by 2 Pinsiders

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#1 6 years ago

I'm having trouble chasing down the cause of a fuse that keeps blowing on my project NASCAR.

None of the YEL-VIO coils fire in the Portal diagnostics (all the others work). Whoever worked on this machine before cut some of the YEL-VIO wires off various coils (perhaps to diagnose or fix???). I soldered those YEL-VIO wires back on to the coils (to the best of my ability) thinking that would close the circuit and solve the issue. However, now the machine is blowing the F21 fuse on power up (but the F6 fuse (removed) is fine, so not sure this fuse issue will solve all my issues, but it would be a good start).

I'm not sure where to start to track down the cause of the F21 fuse (3A SB) blowing. Recommendations on how I should proceed?

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#2 6 years ago

That might be why the two wires were cut from the coil. Problem with that coil, or elsewhere.

LTG : )

#3 6 years ago

Doesn't seem to be the coils (all test okay with the multimeter, even the ones I soldered the wires on). Is there a standard way to troubleshoot the blown fuse issue? I'm not sure how large the solution space is here...

#4 6 years ago
Quoted from Ramtuathal:

Is there a standard way to troubleshoot the blown fuse issue?

Figure out what it all protects, then start going over all that.

LTG : )

#5 6 years ago

Of the 13 coils on the fuse one or more is shorted to ground is someway that you have excessive current flow. It can be a shorted coil, diode or transistor. Since there are 2 groups of coils that are connected by different plugs on the driver board I would remove one connector (j-8 or j-9) and replace the fuse and retest. Once you narrow it down to one group you can remove the control wires from the coils then power it up and one at a time touch the control wire to the coil. The coil that sparks is the bad circuit.

#6 6 years ago
Quoted from GRUMPY:

Of the 13 coils on the fuse one or more is shorted to ground is someway that you have excessive current flow. It can be a shorted coil, diode or transistor. Since there are 2 groups of coils that are connected by different plugs on the driver board I would remove one connector (j-8 or j-9) and replace the fuse and retest. Once you narrow it down to one group you can remove the control wires from the coils then power it up and one at a time touch the control wire to the coil. The coil that sparks is the bad circuit.

Nice diagnosis. I would add to go over every coil specially the ones in the test car scoop, the coil in there gets loose and rotates and touches the metal wall. it's notorious for shorting out.

#7 6 years ago

Thanks for the advice GRUMPY and kvan99 . The issue is not resolved, but I'm narrowing down the cause of the short. I pulled J-8 first because the test car coils (on J-8) were suspect. Powered up and the coils on J-9 worked (pop bumpers, etc.) and fuse F21 did not blow. So, the short is on something powered through J-8 (great advice, GRUMPY). I noticed that the Track Exit Popper (#7) coil lugs had solder touching the coil bracket. There was even a (factory?) piece of thin plastic between the coil and the bracket, but it had worn / burned through and it appeared that the lug solder was touching (and burning on) the coil bracket. I removed some solder and made a new piece of plastic to keep the lug from touching the bracket (see images). I thought I solved the problem, but no luck. Powered up with J-8 plugged in and fried the F21 fuse again.

So, GRUMPY recommended that I remove the control wires from the coils, power up, touch, and look for the spark. I'm not familiar with this method, so I'm wondering if you could tell me more about how to do this. (1) What will spark? (2) Won't I see an arc no matter what? (3) Will the fuse blow every time I try this? I don't have a breaker / fuse made, so I'm going through fuses like crazy already.

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#8 6 years ago

kvan99, I checked that test car scoop coil up and down - not touching anywhere that I can see, but thanks for the heads up.

#9 6 years ago
Quoted from Ramtuathal:

so I'm wondering if you could tell me more about how to do this.

Sure. The coil that you have pictured has a brown control wire. Unsolder this wire and the control wires on the rest of the coils for j-8 and insulate them. Power up game with a good F-21 fuse. One at a time take a control wire and briefly touch it to the coil lug it came off of. If there is a spark then this coil circuit needs more troubleshooting. This should not burn the slow blow fuse as long as you are brief. The coils that don't spark can be reassembled and tested in coil test later.

Quoted from Ramtuathal:Won't I see an arc no matter what?

On coil #7 the power wire was grounding to the metal bracket and may have burnt the fuse even if the control wire was removed. But if you have a transistor that has shorted it will lock a coil on which will also burn the fuse and you wont see a spark. When you remove the control wire the coil will not activate and stop burning the fuse.

#10 6 years ago

GRUMPY - two more quick questions then I'll give this a shot (thanks for being so helpful!).

(1) How do I know which wire is the control wire?

(2) By "insulate them", what do you mean? (Wrap in electrical tape?)

#11 6 years ago

For question#1 you posted a picture of the coil chart table and the color is listed after the voltage.
For question#2 tape or a wire nut.

#12 6 years ago

I used a different method to track down the bad coil. I pulled the wire connectors apart for the control / power wires on the suspect coils until I found the one that popped the breaker (I also made a fuse / breaker thing to save on fuses). Turns out the breaker only pops when #7 coil (Track Exit Popper) has juice - when #7 is disconnected, the breaker doesn't blow and the other coils on J-8 fire without issue.

I originally assumed #7 shorting on its bracket, but I've removed the coil from the bracket (clear of all other parts) and powered up - still pops the breaker when that coil is isolated from everything. I checked the coil (removed) with the DMM on low-resistance and I get ~4.3 ohms. This is confusing to me because that reading (>1) suggests that the coil and its diode don't have a short.

So, if the #7 coil is the problem coil (it is) but not grounding out on the bracket or showing <1 ohms, what is the problem? Do I just need a new coil / diode, or am I missing something?

#13 6 years ago

You know that when J8 is unplugged the fuse is good. You also know that the coil has good resistance. Then you need to look at the driver board for a shorted drive transistor.

1 week later
#14 6 years ago

The problem with the blown fuse / #7 coil has been resolved. For anyone with a similar problem, here are the steps I took to resolve the problem (see images for more):

1) With the machine powered down and the power source removed (unplugged from the wall) for a while, remove I/O Driver board from head, paying attention to where the wire harnesses, etc. were attached (take pictures!). Note: Try not to touch any of the connections on the PCB before draining the capacitors.

2) Drain the main / high voltage capacitors (nine "large" on my board, with scores of small capacitors that were less of a concern) on the board using an *insulated* resistor (the resistor I used was, by the calculations, not rated high enough for the expected wattage, but it still worked. Note: just shorting the capacitor using a screwdriver is NOT recommended by professionals, despite the fact that the advice to use a screwdriver (etc.) is often given by people working on boards).

3) Locate, desolder (using a "solder sucker" like I did (or braided wire, which I did not try)), and remove the suspect component. In my case, it was a MOSFET transistor, labeled Q7 (the transistor corresponding to the coil that was blowing the fuse) for the WhiteStar board (see screenshots of the manual for NASCAR I posted above to help locate the problematic transistor).

4) Test the transistor *out of circuit* (completely removed from the board). There are several YouTube videos on how to test a transistor using a digital multi-meter (DMM), but note that DMM's may not be the best way to test the transistor (several videos suggest constructing your own transistor tester, which was out of my wheelhouse, but not too difficult). In my case, the Drain to Source on the removed MOSFET transistor (Q7) was conducting a relatively low resistance amount of electricity even after it was discharged (this is the "easy" problem). This indicates a bad transistor (see videos). However, DMM's vary in how much voltage they can put across a component, so not all DMM's are suitable for all transistor tests. That is, my Velleman DMM did not seem to have enough juice to turn the transistor "on" in a way that I could test the old or new transistors by turning them on (Gate positive, Source negative) and then looking for issues with the drain rate (Drain positive, Source negative, until "empty"). However, I still was able to use my DMM to test the suspect transistor, so give it a try with what you have once you understand the way MOSFETs work.

5) Find a replacement transistor. I ordered my STP22NE10L (a IRL540N MOSFET transistor, I think) from Marco's for $2.99 + shipping. Marco's specifically listed this transistor as a "Q1-Q16" replacement, so I was confident that I ordered the correct part because I was replacing the Q7 transistor. However, I had trouble confirming the part was the correct replacement by using the Stern manual / Stern forums - it seems that I lucked out with the description Marco's gave for the part. The transistors typically (but not always) have part numbers printed on them. Make sure that you replace the component with a compatible part - otherwise, you could destroy your Driver board, damage your machine, etc.

6) When the new part arrives, test it the same way you tested the old one. In my case, the new transistor did not conduct electricity between the Source and the Drain, but the old removed transistor did. This was good news for me; something should function differently between your old part and the new one if you are hoping to solve a problem with the new part.

7) Insert the new part into the board in the correct orientation (again, make sure you take pictures and understand the Gate, Drain, and Source order of the transistor).

Gently pull the leads apart so that the part stays in the board while you solder it.

9) Put some flux on the leads and the "holes" on the board.

10) Use your soldering iron - CAREFULLY - to heat the lead and PCB hole to the temp that it will melt the solder (Note: do NOT use acid-core (plumber's solder), use rosin core tin / lead mix solder). This is tricky - the temptation to apply the solder directly to the soldering iron is immense when using a cheap iron. However, this can lead to cold joints / bad solders, so don't do it. The part and the board could get very hot in the process - this is just how it works if you don't have a temp-controlled iron. Apply a small amount of solder and connect the part to the board (there are tons of YouTube vids that show how to properly solder on a PCB).

11) Make sure you have good solder joints (by visual inspection, and make sure that your solder isn't making connections across joints) and clip off the leads of your transistor so they are no longer than the clipped leads from original production.

12) Reinstall the board in the head and, with fingers crossed, fire up the machine. In my case, replacing the suspect transistor solved the problem.

I have never worked with PCBs or electronics soldering (I've soldered some EM parts, but never PCB components). I did about three hours worth of research and the whole process took less than 30 minutes to complete. YouTube is exceptionally helpful, as is the advice on Pinside (thanks GRUMPY !). I bought this machine from someone who said it was "hopeless", but, after 3 hours of research and 30 minutes of labor, and a $3 part, I was able to take an unplayable machine and make it into a machine that was 90% operational (still some switch issues, but nothing too major, I hope). If you feel overwhelmed or confused, just remember that all mechanical / electronic things can fail, and all mechanical / electronic things can be fixed.

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#15 6 years ago

Nice job, now play ball.

#16 6 years ago

Nice work!

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