Those Eddy boards do go bad over time and since you have tried
adjusting it and keeps doing the same thing it would be a good
idea to go ahead and replace it.

"Eddy" boards??? What exactly is "Eddy"? I don't know that's why I'm asking...

The potmeter could have gone bad and its worth a shot to
change it if you dont plan on buying a new board.

Ah, thanks for explaining that. It's a wonder they don't pick up on all the electromagnetism under the play field.

When they go bad you will see it. They will 'cook' and the top will open up and look like corrosion is growing, the plastic will receed from the top and they swell up.

Good point

The adjustment middle part in the pot becomes weak I believe, and will start to move with vibration. I don't know if you can find them, but that would be the thing to replace in my opinion, however I'm not sure if I'm correct in this 100%. The left hokus pokus on my ToM needs re-adjusting about every 3-4 months, so nothing I'm concered with now, but if it became even a weekly thing, I'll review my options.

Do you notice any visible change in the adjustment once it stops working, as is, where you previously set it, it apears it has moved? If so, I might try setting it, and gluing it there. You could always heat that up later to remove, and if it doesn't work, it's not like you're hacking anything that won't be replaced anyway.

C3 should be removed regardless of the condition. Read this:

http://www.pinbits.com/index.php?main_page=product_info&cPath=13_4&products_id=188

Heres some info:Adjusting Eddy Sensor Boards.
Often eddy sensors can go out of adjustment and become less sensitive. This can cause the eddy sensor to not activate when a ball passes above it on the playfield. To adjust an eddy sensor do this:

* On the under the playfield eddy sensor control board, turn the potentiometer counter-clockwise until the LED just turns on.
* Now turn the potentiometer back clockwise until the LED just turns off.

That is all that is required to adjust the STNG/ToM/RS eddy sensor. To test the sensor, put the game into WPC diagnostic's first switch test. Then move a pinball over the playfield area where the eddy sensor is located. The switch should activate on display. Also from the bottom of the playfield, the eddy board LED should go ON as a ball passes in front of the eddy board's senssor (this can be seen anytime, the game does not need to be in switch test.)

Different R1/C1 Eddy Sensor Values (Fine Tuning).
Because the ball sensors are different on some games, the value for R1 on the Eddy sensor boards can be different. For example, on Star Trek Next Generation and (two of the eddys on) Theatre of Magic), R1 is 4.7k ohms (these games uses the small ball sensor). But on roadshow and the ToM trunk, which uses a much larger ball sensor, R1 is 2k ohms. So if you switch an Eddy board between these games, the Eddy R1 resistor may need to be changed to the correct value.

The purpose of the R1 resistor is to make the adjustment pot "centered" for the particular ball sensor. For example, if you use a 2k ohm R1 eddy board in STNG, the adjustment pot will be turned almost all the way up (with very little adjustment range). It still works most of the time, just the adjustment range is not centered.

With this in mind, I once had a roadshow where I could not get the eddy board's LED to turn off, no matter where the adjustment pot was moved. Normally roadshow uses 2k ohm R1 resistors for all three eddy boards - but in this case I had to replace the R1 resistor with a jumper wire (0 ohms). This put the adjustment pot about dead center, and the eddy boards worked great (with the 2k ohm R1 resistor, the eddy boards would not adjust, and hence would not work.) Another trick is to change the C1 cap to 3300pF, which widens the field of the eddy sensor a bit

hmm, good read.

Also, have you checked that the connector is okay on the board that's not working well? On my TZ (I assume these are the same kind of sensors as TZ uses to detect the powerball), I've never had to adjust them, but the connectors are really dodgy, and i've had to reseat them numerous times.

No they are not the same boards as TZ, TZ has proximity sensor board.There is only
one eddy sensor in TZ and its in the ball trough, but it's a different design than the STNG/ToM/RS eddy sensor.

Does this apply to the trunk in TOM? My trunk does not register hits every time? Is this an eddy sensor and do I follow this advice? Thanks.

Yes,This info also applies to TOM and you might want to check this out if you plan on changing the trunk board pretty cool design and it adjusts itself http://pinbits.com/index.php?main_page=product_info&cPath=13_33&products_id=375

Thanks pinmike, that looks excellent

There must be a component on the board this is shorting out when it heats up, which makes me think it is an IC. My knowledge base ends there. Try checking RGP for anything similar to your issues. Is a resistor slowly going open...?

This "sounds" like it might assist, but you may want to spring for the pinbits replacement at this point. I hate recommending a cop out like that, but I don't know what else to tell you, unless someone else has anything to add.

Sensors do go bad.

As for pinbits, they seldom go out of stock for anything. The website states this, but when you call, they usually have them, just haven't updated the site. They are a "mom and pop" shop so to speak, so their system gets updated when they get around to it.

would anyone be willing to post some pictures of what you are adjusting and where its located? im a total n00b and am just totally lost on if my game has all these same control boards. my road show dozer sensor hasnt registered hits since i got it. i pulled up the play field but was totally lost. im slightly nervous to adjust stuff with power on, but im guessing thats necessary. thanks for any help.

It will be on the underside of the playfield around where the dozer is (apologies but I dont have a RS to take pictures for you). Look for a board like below. In the middle to the left of the red LED there is a black box with what looks like a screw head. That is what everyone is talking about adjusting. Theatre of Magic uses the same type of sensor. I turn it all the way until it doesnt turn anymore. The red LED will be off. You the turn it back slowly and once the LED comes on you want to stop. Your dozer should register now! If not it's possible you have a bad sensor and it needs replaced. Best to purchase the sensor from Pinbits as they're self calibrating thus you never need to adjust them!
http://www.pinbits.com/index.php?main_page=index&cPath=13_25
wmseddy1.jpg

Y'all are awesome! Dozer works! Kids are cheering...ok it's really me cheering :p

Good to hear. Now these sensors can go in and out regularly so don't be surprised if you're adjusting it again!! One thing you can do is take some locktite or even nail polish and put a dab on that screw-head once you have it calibrated. By doing this it will keep the screw-head in place and limit the number of times you will need to re calibrate it!

I know this is a relatively old thread but wondering if someone could identify the IC used on the Eddy Sensor board, the williams manual does not list a specific IC.

Or you could even replace the pot with a fixed value resistor, once you have it set where it works consistently.