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Dr Who opto board mini playfield fault

domlouis

domlouis

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May 28, 2014
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Guys please help me.

My Dr who has had this fault for ages: one of the 5 targets on the mini playfield does not register. It is annoying. My limited understanding is that the back of the target is meant to break an IR beam between two opto boards (a sender and a receiver). So i presume that the problem is with the boards. In test mode i can recreate the fault: it doesn't register a hit.
I am able to completely remove the mini playfield from the machine to examine the boards but then i can't test it any more as everything has to be disconnected to lift the mini playfield. So i can't see if it is really a board issue or an alignment issue. Does anyone know how to test an opto IR board with a voltmeter?
Please keep it simple.

Thanks

Dom
 
Jim @myPinballs just shot-gunned the opto's on his Dr Who time expander board so I'd suggest probably doing the same. Replace the transmitters and receivers for all 5 targets and also reflow the solder on the header pins and you'll probably find the problem solved. When removing and then re-fitting the board also check to see if anything is damaged or missing with how it mounts because I think it should all line up fine, as in I don't think it's got any adjustment in it.
 
ronsplooter said:
Jim @myPinballs just shot-gunned the opto's on his Dr Who time expander board so I'd suggest probably doing the same. Replace the transmitters and receivers for all 5 targets and also reflow the solder on the header pins and you'll probably find the problem solved. When removing and then re-fitting the board also check to see if anything is damaged or missing with how it mounts because I think it should all line up fine, as in I don't think it's got any adjustment in it.
Click to expand...

Absolutely. Just change all 5 optos and receivers if you take the assembly apart as its not worth the hassle of having to do it all again if another opto fails later on. I sell 10 opto pairs for £12 plus postage so its not going to break the bank just to replace them all.

You can test the opto boards assembly separately once removed and repaired as the opto assembly plus mount is separate with its own cable connector so you can just lift the playfield up and plug this part back in to test in the switch test. This is what i did and is pictured in my repair log
 
You don't need to remove the mini playfield in order to remove the opto assembly. Just have the mini playfield in the down position, raise the playfield. Remove the ball trough in front of the Optos, then remove the four (maybe if they were replaced last time) screws that secure the black moulding. Unplug the wiring connector, snip a cable tie if still in place and wiggle the opto assembly out, taking note of how the wiring is threaded through the playfield. Plug the opto assembly back in. Look for broken Optos, and cracked solder joints. If the moulding is severely warped then it may need replacing as the light beams will not connect with the receiver. You can remove the sender side and ascertain if the senders are working by aiming them in turn at a working receiver. Then test the receivers.
 
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