PC-9821 Motherboard Trace Damage

[98digger]

Hello NFG,

I just got my PC-9821 Ce2. I went to open it up to examine the motherboard and I did something incredibly stupid; I accidentally slid the CD-ROM caddy's leg into the motherboard and caused some damage. 5 traces DIRECTLY under the screw-hole have been scratched and the copper exposed. When I realized this, I kind of jumped and accidentally jabbed the other CD caddy's leg into the left speaker .

I have not been able to test it because my voltage converter has not come in yet. I really have no idea on how to fix this, which is why I am posting here. Below is the damage (it is right underneath the screw hole. The line and dot in the unpopulated area to the right of the copper circle is actually a hair or something):



The traces appear to have been exposed, but I don't know if they are crossed into each other. They are small traces, so I cannot really see them well. The rest of the Motherboard is perfectly fine.

As for the speaker, the good thing is that I just scrapped several IBM-Compatibles today with similar built-in speakers. I can easily swap that out with one I salvaged.

Actually, this is not the first game system/computer I have accidentally ruined. My first Sega Genesis did not turn on, and I thought it was the cartridge slot, so I tried to clean it with paper towels. But they got stuck in it, so I tried using a razor to get it out and accidentally snapped off some pins. The sad thing is, it was actually the power adapter that was the problem; I swapped it out and it actually did turn on.

So, what do you guys think I should do? Should I just cover it using a green PCB overcoat pen? Should I put epoxy on it? Is there a place where I can buy a new motherboard? Is there any place that will repair this for me? Any help is appreciated.


Thanks! 

[caius]

Test with a multimeter if there is continuity between two different places of each trace (first scratch the solder mask to expose copper ).Anyway I think they are good, you have only removed the solder mask.

[98digger]

Test with a multimeter if there is continuity between two different places of each trace (first scratch the solder mask to expose copper ).Anyway I think they are good, you have only removed the solder mask.

Hello,

@caius:

Thanks for all your help. I was kind of afraid there that it might have been worse. Although, I think that I should mention that the scratch kind of "smudged" the traces (this is the best I can describe it) upwards. I don't think the smudges are each touching more than one trace, but I could be wrong. Below is a drawing I made that better clarifies what I am trying to describe:



So, if it is fine, can I just go ahead and recover the traces with a green overcoat pen? I don't really want to expose any more of the traces to test it with a multimeter. Although, I will dig out a magnifying glass and look it over closely before doing that.

Also, the back of the Ce2's faceplate has some weird "root-like" marks on it. I don't know if it is mold or something, but it is easily removed with a Q-Tip. Actually, today I was scrapping Pentium IBM-clones and noticed the same thing on the faceplate of those. Does anyone know what it might be?

Thanks,
-98digger

[SkyeWelse]

Sorry to hear that you may have done some damage to the traces on the motherboard. The damage doesn't look terrible from the photos that I can see. While I'm not an expert on repairing electronics, and rather new at it, I did recently repair some traces that looked far worse than this on a power supply unit for an external 5.25" FDD drive. Here are some photos of how bad the damage was:


Bad trace damage due to leaky capacitors
After Fixing

In my case, I had some help from a friend identifying the problem areas that needed to be tested with a multi-tester, but sure enough testing the connection with the multi-tester to find if the traces had no resistance was beneficial and I soldered jumper wires (cat-5 cable wires) to bridge the bad connections.

Perhaps a trace pen would help, but I've heard that they did to flake off overtime if you are not careful, but I'd definitely test the bottom and top of the exposed copper areas first with a multi-tester either way to see if this repair it even necessary. Then once you do have a solid connection between the two points you can slap a slice of electrical tape or glue over it (if you want to go the permanent route) and call it a day.

I think I have some squiggly root-like patterns on the back of my case as well. I think it's just odd moisture patterns probably from long-term storage in a climate that maybe wasn't ideal.

Good luck!

-Thomas

[98digger]

Sorry to hear that you may have done some damage to the traces on the motherboard. The damage doesn't look terrible from the photos that I can see. While I'm not an expert on repairing electronics, and rather new at it, I did recently repair some traces that looked far worse than this on a power supply unit for an external 5.25" FDD drive. Here are some photos of how bad the damage was:


Bad trace damage due to leaky capacitors
After Fixing

In my case, I had some help from a friend identifying the problem areas that needed to be tested with a multi-tester, but sure enough testing the connection with the multi-tester to find if the traces had no resistance was beneficial and I soldered jumper wires (cat-5 cable wires) to bridge the bad connections.

Perhaps a trace pen would help, but I've heard that they did to flake off overtime if you are not careful, but I'd definitely test the bottom and top of the exposed copper areas first with a multi-tester either way to see if this repair it even necessary. Then once you do have a solid connection between the two points you can slap a slice of electrical tape or glue over it (if you want to go the permanent route) and call it a day.

I think I have some squiggly root-like patterns on the back of my case as well. I think it's just odd moisture patterns probably from long-term storage in a climate that maybe wasn't ideal.

Good luck!

-Thomas

Hmm. I would try to test the traces with a multimeter, but they are waaay too small for any multimeter I have. They are like 0.05 millimeters in width. Perhaps there is some electronics repair store around where a professional can take a look at it. I'd assume you would need a really nice magnifying glass and really thin multimeter prongs in order to test it, and a pretty small conductive material pen to fix any problems, all of which a professional probably has. I do in fact think this is a fixable problem, however, because numerous people have succeeded in modding (and sometimes repairing traces) their Xbox 360 consoles, which have traces half the size of the ones in the 9821.

But, yeah, I think I'll first off examine the traces myself with a good magnifying glass or device. If I don't find anything too bad I'll just wipe some green-coating fluid over it and call it a day. If it is really bad (which I kind of doubt now after taking another look at it), I'll definately bring it to a pro. I have really no oportunity to get another PC-98, and this one is otherwise perfect (the BIOS is actually on a MASK-ROM instead of an EPROM. As the 2bitgamer once said "If it is broken, fix it. If you can't fix it, fix it anyways."


Thanks for all the help!

-98digger

[acridAxid]

When using a multimeter, you don't actually test on the traces themselves.  You test at the solder points (where each end of the trace ends on a solder pad).  You'll know it is unbroken because the meter can read itself through the entire length of the trace.  If it were severed, you'll get no reading.

You don't need an "professional", maybe just someone who has used a multimeter before to help you get it on the right setting and find the right solder pads to test on.  This kind of testing is fairly simple and one of the first things you will need to learn to do when working closely with electronics, so you might as well figure it out now.

[caius]

When using a multimeter, you don't actually test on the traces themselves.  You test at the solder points (where each end of the trace ends on a solder pad).  You'll know it is unbroken because the meter can read itself through the entire length of the trace.  If it were severed, you'll get no reading.

Yes, this is right but only if you know where are both ends of  the traces!
My advice is to test continuity between two points of the trace in which there is the damage.In this way you can know if they are severed or not.So, remove a bit of soldermask after and before the damage and test continuity between these two exposed points.

[98digger]

Today I managed to find two magnifying glasses, and proceeded to try and investigate the traces closely.

Turns out, all the traces are perfectly intact (at least from what I can see). At first I though I might have seen a break in one trace, but after I moved the lighting and looked even more closely, I realized that what looked like a break was actually a scratch (and/or imprint from impact) over two traces, which caused the light to reflect strangely. There is actually still some solder on parts of the traces, which at first made me believe that they might be crooked. But, yeah, they look fine.

I did try seeing if a multimeter prong would even fit on one trace, and unfortunately it did not fit. I tried tracing the traces to solder pads, but these traces just merge into a whole bunch of other ones, and then a whole maze of traces, so I could not really do that. But, as I said, the traces are fine anyways.

While staring at the traces for a good half hour, I did notice some tiny metallic pieces that are about the size of sand grains on the board. They don't look copper-color (from what I can see), so I think they either were produced while unscrewing/screwing in the screw directly above, or from the CD-caddy leg, which has scratches on it from colliding with the motherboard.

SO, I think that all I need to do is reapply the solder mask with a special pen; I think this one might work:

https://www.chemtronics.com/p-710-circuitworks-overcoat-pen-green.aspx

And then after that, I believe I should be O.K. for using the PC-98. 

-98digger