Twilight Zone Proximity sensor

[andtan]

Been having some issues with my TZ promixity sensor - the trough one - switch 26. The LED on the board is always on, and is doesn't ever go off as it should when the Powerball is the next ball up.

All the info I can find relates to it not detecting the metal balls, but this is the opposite. I have removed the board from the bottom of the PF in case it was too close to some other metal, but the LED is still on.

The only mod that has been done is someone soldered the wires from the driver board to the proximity board. The coil has been hit once or twice before, but seems ok.

Is there a simple answer to this one that anyone knows of? There isn't too many items on the boards, so I'm hoping it's not too difficult. My next step is to unsolder some components and test them individually.

Cheers,

Andy  

[dendoc]

Beaky fixed mine in about 10 minutes - over to you to let him know what the hell you did..................................

[Homepin]

Isn't there a small trimpot on the board that goes cactus and needs replacing?

[andtan]

Isn't there a small trimpot on the board that goes cactus and needs replacing?

No trimpot on mine Mike, I believe that that may have been added on later models. One board has the coil, the other board (driver board) has a couple of IC's, some diodes, resistors, and small caps.

[beaky]

until it is in range of my magic wand there is not much i can recommend.
I can't even remember what i did to fix yours John. 
I really need an external hard drive hooked up to my brain because my memory is full 

I think to memory it was a dry / cracked solder joint. the wires were soldered directly to the pins on the connector but the connector had cracked solder joints at the board.

I replaced the pins, housing and headers. re-flowed all the components and it has been fine ever since. and it can even be UN plugged if it needs to be removed. I don't believe in hard wiring any connection that came out of the factory with a connector and worked for years with out any great dramas,

 

[andtan]

I think I found the issue.

When I was pressing on the coil, I managed to get the LED to briefly go off a couple of times. I unsoldered the coil and checked with a multimeter and found that the circuit wasn't complete. I then checked around the area that had been hit with the balls a few times and found the break to be there. As the coil is really small I tried dabbing a bit of solder where the break was hoping that this would solve the problem.

Unfortunately, whilst the coil is now continuous, the LED remains lit. I assume that the solder fixed the break, it may have changed the resistance of the coil, and the ciruit still thinks the ball is present. Oh well, it looks like I'll be looking for a new coil (A-16393) which doesn't look promising. If I can't find a coil, it looks like a replacement board set.

[Homepin]

The coil is very likely to be wound using enamelled copper wire. It might LOOK like bare copper but you will need to scrape the varnish with a sharp blade away before soldering.

It is almost impossible for the inductance of the coil to change to any degree large enough to matter - even if you were to take a turn or two off - they simply aren't that critical.

[pinball god]

I may have a coil as a spare. Take a photo so I can compare.

[andtan]

I may have a coil as a spare. Take a photo so I can compare.

Thanks Pinball god, here's a link which has a photo of it.

http://www.pinball.co/Products/13834-a-16393.aspx

Cheers,

Andy

[pinball god]

Will have a look this week, been working at the melb garden show with no breaks until tonight so absolutely beat

[andtan]

Thanks mate