Circuit Board Electric wiring Questions

[chumch]

I'm working on getting my Pinball machine in better working order and I have a couple of questions that are perhaps more generically related to circuit boards. From the pic below, you can see the burnt wiring harness housing at the top. I want to replace that with a better style (one that contacts the pin on the board at 3 points instead of just one, which is presumably what caused the burning in the first place). My question is how to you do a feed wire housing (where each wire goes into the housing at one point) when on the current set up there is this looping of the wire to effectively send current from or to one wire at two points on the board. Do i need to splice and if so how, just create a "Y"?

The other question is what is the function of a polarizing pin (poorly pictured below)? It is a plastic pin that seems to be placed into a very specific location into the wiring housing at a point where no pin will be entering the housing from the curcuit board. It just seems like it cant possibly do anything as I look at how and where it sits and what it is made from.

Thanks!

Matt

 

[comtec]

How many loops come off the feed to the block?

A polarizing pin in placed into a connector to block a pin position to keep the mating plug from being plugged in backward.

Mike


Looked again, seems like each feed connects to two positions with the use of the loops?

 

[chumch]

There are 4 loops. Some wires do not loop...they only occupy one position in the housing and therefore on the board (for example, the top wire, the one that is burnt is not looped)

 

[comtec]

Ok Matt, i think i know what your saying. You really only have two options, either running another wire from the feed location for the additional connection point or creating the "Y" in the cable. I would solder the connection point and cover with heat shrink rather then using the consumer available wire taps. A compression tap would be the best to use but you might not have those available.

Do we know what amp the cable is carrying?

Mike

 

[bambbrose]

Can you get a better picture of the terminal block housing holding the loops? Does it disconnect?

It appears the loops are simply jumpers to connect each load to multiple points, nothing more.

By replacing with three wires, you aren't fixing anything. That is the same as replacing with one thicker gauge wire. Although it may offer redundancy, it also offers 3 points for shorting. Pick your poison kind of thing.

The best thing you can do it replace it with one gauge thicker of wire than the one that burnt out, ensure you have a great connection with low resistance, and replace the fuses because they obviously didn't do their job.

If you can get the dimensions/specs of the connector, we can probably find the modern equivalent form AMP or TE. Modern connectors have higher fire resistance ratings on the plastic.

 

[chumch]

Can you get a better picture of the terminal block housing holding the loops? Does it disconnect?

It appears the loops are simply jumpers to connect each load to multiple points, nothing more.

By replacing with three wires, you aren't fixing anything. That is the same as replacing with one thicker gauge wire. Although it may offer redundancy, it also offers 3 points for shorting. Pick your poison kind of thing.

The best thing you can do it replace it with one gauge thicker of wire than the one that burnt out, ensure you have a great connection with low resistance, and replace the fuses because they obviously didn't do their job.

If you can get the dimensions/specs of the connector, we can probably find the modern equivalent form AMP or TE. Modern connectors have higher fire resistance ratings on the plastic.

The housing does come off and I do have access to better housings. I have replaced one already with it. The whole purpose of the better housing is to give a better (multipoint) connection to the pin--that was my reason for changing them. I guess when they manufactured these machines they used a connection that was good for the assembly process but not good for long term high current flow.

Why do they do those "jumpers"? What is the purpose of them? So if I do a "Y" connection I should use a higher gauge wire for the top part of the "Y"?

Thanks for the help!

 

[comtec]

The wire didn't fail, the connection point did and it is already feeding both so the "Y" shouldn't require a larger wire. I have seen failures that look like yours and they were caused by vibration causing the mechanical connector to become loose and the wire started arcing inside the connector without blowing the fuse.

Mike


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