Marble Madness. What are the white rails?

Arcadenut

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I am working on the older Marble Madness board that looks like this:

marble.png


One of the rails broke off, and rather then try and re-attach it, I was wondering if I could just replace it's function (i.e. if it's just a Ground, then run wire, etc...).
 
They are tied into the ground points, but I think the primary function of them is to provide additional structural support. They prevent longer boards from flexing in one direction.

Flexed boards lead to cracked solder joints, cracked CHIPS, and broken traces.
 
They must do something. Are they resistor packs, or something?

I had a board that one broke on, and the board stopped working.
 
They are just power rails. Usually they link the grounds and any circuit that needs extra current carrying capabilities, like the 5vdc circuit. By using these rails the board itself can be manufacturered cheaper, the rails can be as large as the designer feels they need to be, and their placement in the open air helps cooling as well.

If the rail breaks on a board it could cause the board to stop functioning, especially if the rail is the only link in the circuit to a critical component.
 
Can these be replaced? I've never seen them anywhere.

I had one come off of a DK3 board in a couple of places and they worked fine, once resoldered.
 
I have never seen repacements but I have used wire and pins to replace them without any problems.

I guess my question is, is it just a direct solder from one pin to the next, or is there something else I should be aware of. From looking at them, I find it hard to believe that they are anything other then a giant jumper that connects ALL the pins together.

However, before I just connect all the pins together I just want to make sure it's not something like a giant resistor array.
 
They are just pieces of metal. There is no resistance or capacitance. They could just as easily have used a piece of wire instead of the rails. So, yes you can connect all of the points together with any conductor such as wire or a piece of metal.
 
They are just pieces of metal. There is no resistance or capacitance. They could just as easily have used a piece of wire instead of the rails. So, yes you can connect all of the points together with any conductor such as wire or a piece of metal.

Well after more testing, it's not that straight forward, at least with the rail I am fixing (and might be true for the other rails, but not 100% sure at this point).

I tested the one I am repairing and found that all the even pins are connected together and all the odd pins are connected together.

So its like this:

1 3 5 7 9 11 13 15 17 are connected.
2 4 6 8 10 12 14 16 18 are connected.

one set is +5V and the other GND.
 
Well after more testing, it's not that straight forward, at least with the rail I am fixing (and might be true for the other rails, but not 100% sure at this point).

I tested the one I am repairing and found that all the even pins are connected together and all the odd pins are connected together.

So its like this:

1 3 5 7 9 11 13 15 17 are connected.
2 4 6 8 10 12 14 16 18 are connected.

one set is +5V and the other GND.


Are all of the even on one rail and all of the odd on another, or do all rails run both? I have seen where alternating rails carry +5vdc and ground. I have never seen one rail that runs both, but it is possible and still wouldn't be hard to replicate.
 
Are all of the even on one rail and all of the odd on another, or do all rails run both? I have seen where alternating rails carry +5vdc and ground. I have never seen one rail that runs both, but it is possible and still wouldn't be hard to replicate.

It's one rail that appears to run both. Now I can only confirm this for the rail closest to the Slapstick, haven't really tested the others and might not be as easy being in circuit.

Two of the EPROMS were not getting +5V, so I found the points where the rail was soldered in. Those points were not getting +5V so I jumpered them. After that the chips were getting +5V.

Now I just need to track down why it's coming up with "No Cartridge".
 
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