a general circuit board question

vintagegamer

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If one were to need to dremel away a little bit of the edge of a board to access a component underneath of it, how damaging is that to the board being "trimmed"? The board in question has the traditional ground trace all of the way around the edge that might require a little shaving.

Just wanted to hear what kind of impact this will have, if any- we're talking 1/8" max.

PS this would just be in ONE SMALL SECTION of the board, not all the way down the edge.
 
I am not sure why you would need to trim the board, but as long as you don't completely break the ground trace you should be fine. How thin will the ground trace be after the mod is done?

Understand that the ground trace is now exposed to whatever the board contacts in that area, though.
 
If one were to need to dremel away a little bit of the edge of a board to access a component underneath of it, how damaging is that to the board being "trimmed"? The board in question has the traditional ground trace all of the way around the edge that might require a little shaving.

You can trim down the edge of a board, and trim into ground traces. It's not a big deal, provided you know exactly what you're cutting through on both sides of the board. Beware multilayer boards - most arcade boards are only double sided, but, for example, computer motherboards are four or more layers. Hold the board up to the light and see.

If you're just talking about cutting into a wide ground trace and making it narrower in one place (but still connected), no big deal. If you have to cut the trace completely, just jumper around it with wire.

One thing to be very careful of is that when you cut the board, that you don't have little overhanging flakes of copper from the cut. For example, when kludging RAM into an old computer system, I was taking 30 pin SIMMs and soldering wires from the pins on the SIMM and connecting them to the board (since suitably sized DRAM DIP chips weren't available). The SIMMs were a bit too long to fit, so I trimmed them down (only ground/power planes stuck out to the far edge of the module). On one layer, the large plane is power, an on the other, ground. By cutting it, I managed to short between power and ground with a little bent-over shard of copper. On powering up the computer, it blew out the short with a suprising puff of smoke and a pop...

So, after cutting, scrape the edge of the board with a knife to make sure you clean off any possible shorts...

-Ian
 
I am not sure why you would need to trim the board, but as long as you don't completely break the ground trace you should be fine. How thin will the ground trace be after the mod is done?

Understand that the ground trace is now exposed to whatever the board contacts in that area, though.

Sigh, I know what I'm going to be told after I post this, but I will post anyway. The boards in question have been soldered together to bypass the original interface cables. I have been told that to work through one of the switch issues I'm having, I should swap out one of the chips on one of the 2 boards (the driver board). At the top of the chip is where the overlap of the 2 circuit boards is taking place. I want to shave away a little of the upper board if possible to be able to remove the chip in question and solder in the new one.

Everything else in the game is working as it should (including diagnostics) so if this one chip swap will make the game work 100%, I'd rather do that for now than do the other repair which might end up doing more damage than good.
 
The problem with what you want to do is that you don't know what's on the other side of the board... Unless you're sure what is on the other side of the board, and you know what you're cutting into, don't do it.

But, if you know what's on the other side, and you won't cut any important traces, then go for it. Just be careful not to short between the layers.

Cut it, then try it out - see if it still works the way it did before. If you cut something important and it doesn't work anymore,then you'll have to desolder the interconnect and take it apart anyway...

-Ian
 
I'm gonna take a look at the specs for the board I'm looking to trim and see if there's anything there beforehand.

Appreciate the input!
 
Another thing you could try -- If there is enough room, cut the current chip off the board with cutters, or a dremmel. Then, you should be able to clear the solder holes with desoldering wick or other. Then, carefully bend the legs on your new IC upwards instead of downward. This will allow you to mount the chip from the bottom where you should have full and easy access (unless this is board is in the center of a 3+ board stack...).

This avoids cutting the upper board, and can be undone if need be. It will be a little ugly, and you won't be able to read the chip, but it should work for a standard DIP chip.
 
Thanks all, thankfully I did not have to do this at all. The chip came out with a little work, and I was able to reach the heat ring for where the new legs would go with the edge of the soldering iron so it heated enough to take the new solder.

WHEW!
 
How are the boards attached to each other? Did they just take out connectors and run pins through the holes? Or is it some kind of horrible hack that involves edge connectors? I'm just curious, as I haven't run into that before.
 
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