Old circuit board help, need these LED's and advice.
 

This board is from a tool changer on an old Brother™ CNC machine. Apparently it uses these LED's help to determine tool location,position etc... Well, somehow we managed to crack one LED off the board terminal style. So, how am I going to find such a lil bastid? The machine is from the early 80's so I doubt I'll get any factory support. Any help is greatly appreciated!!!

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Len,

That would not be that difficult to make from scratch. Used to do it years ago and its not rocket science...

Anyway you could just jumper across the bad section?

Thanks Joe, I don't need to make a board, just replace the LED. The problem is: How do I determine what LED to purchase and where do I get it?

Len,

"LED voltage drop is the voltage drop across the LED (typically about 1.7 - 3.3 volts; this varies by the color of the LED"

Go to Radio Shack and get a series of colored LEDS and clean up the solder joints on the board and solder a new similar (Same Color) in the through holes. Watch the polarity. Some upper scale electronic stores will tell you the type of diode it is and sell you one.

I occasionally fool around with electronics.


My .03 cents

Bob

Bob, I already did that (went to RS and got an assortment) but they had various voltage ratings and sizes. Also they are all 2-3 times larger than the one I am replacing. How would you determine polarity anyway? Thanks.

Do you have access to a schematic?
Otherwise, there are a lot of variables. Is the machine looking for a specific color?...specific intensity? Is that a cylindrical LED, or does it have a cover/lens on it? What voltage is supplied to the LED?

You may want to check through a catalog from a supplier like www.mouser.com
Cylindrical LEDs are at the bottom of this pdf page: http://www.mouser.com/catalog/631/115.pdf

The cathode is the positive terminal, and is usually indicated by a notch or flat side of the LED.
http://www.us.kingbright.com/images/catalog/SPEC/WP483GDT.pdf

No schematic, but you confirm my fears of multiple variables. Hmmm, I'll post a couple detail shots of the LED.

Here are some more pics. The LED's actually have writing on them. The one with a "5" on it is the one that came off. It is one of five in that bank. The other side uses a bank of five with a green Chinese/Japanese letter or something on it. Hopefully these pics help.

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Try Radio Shack

Try www.digikey.com
You might give them a call... I'd need more info to ID the LED. They should be able to help.

You also may want to call a local shop that repairs pinball machines, some of them use little optics like that to determine where the ball is or when to trigger certain things.

Thanks guys, I'll make some calls tomorrow. I've actually heard that Brother's customer service is pretty good, we'll see:)

Also the typically the longer wire is the positive side.

If you want to do a bypass it might be smart to use a diode rather than a straight lead.

My .03 which is equal to the cost of the parts that you need.