This is a common problem. It's the sensor in the ball trough. It's just a tiny metal detector. If you look under the playfield at the trough you will see a tiny circut board right in front of the first ball. Make sure the round sensor on the little board is aiming at the ball. Sometime this will get hit by the ball and will be moved. Instead of reading that a ball is there it reads the metal of the ball trough so when the ball is ejected it still thinks there's a ball there.

There are two screws on this little board for adjustments. Just loosen and move it.

Also follow the wires to another small board with an led light. Make sure the plugs are on good as they can become loose from the ball eject vibration. The led light should go on when metal is detected and off when it doesn't.

The slot machine will not register the powerball so you have no problem there.

I hope this helps.

Just to add to wesperron's advice. I've heard that if you put about twelve twists in the double wire connector between the two little sensor boards, it could fix this issue. Sounds weird, but it seemed to work for me. I also made sure like wesperron said, that my little sensor was aimed directly at the ball in the trough waiting to be served into the shooter lane.

Next to the clock, the trough proximity switch is probably the most problematic thing in a TZ. One of the main issues is that the tiny molex connector used to connect the main board to the sensor board is just not very well suited for the task. Over time, the connection will become loose due to vibration. Because of this, many people choose to ditch the connector and solder the wires directly to the board. If you aren't comfortable with soldering, another option would be to purchase a replacement eddy cable such as this:

http://www.pinbits.com/index.php?main_page=product_info&cPath=13_2&products_id=294&zenid=tu4g24vv18i478a89o8nulvro0

TZ_Eddy_Cable.JPG

If you are still having problems after trying all of the things we have suggested, you may need to replace the boards. Fortunately, they are readily available, and the new boards are much better designed. I swapped out both boards in my TZ with a set I purchased from MAD Amusements. The same ones are also available at Marco Specialties:

http://mad-amusements.com/product.php?id_product=737
http://www.marcospecialties.com/product.asp?ic=A-16533-PP

I forgot to attach a picture of the new boards:

TZ_Proximity_Boards.jpg

I have an issue when the power ball comes up into the shooter lane it doesn’t register its there

I had the same problem with the ball not registering in the shooter lane. I adjusted the sensor, still had issues. I finally replaced the cable that Gweempose has shown a picture of and it resolved the problem. The real issue was where the cable connected to the board.

I believe the "twisting" of the wire connector is done to put a constant bit of torque on the board's pins to provide a more consistent connection. If you read Pinbits' description of their replacement connector, they mention the fact that their wires are "tightly twisted". You may want to try this before buying boards or connectors. It worked on mine.

I believe the "twisting" of the wire connector is done to put a constant bit of torque on the board's pins to provide a more consistent connection.

This is what corrected my problem, dont buy anything yet...

Welcome to.......the Twilight Zone......i to am waiting on a new sensor, must be that time of the month for TZ..

Incidentally, I had been plagued by switch 26 errors ever since I first owned the machine. Every time I thought I had it fixed, it would start acting up again a few weeks later. I finally couldn't take it anymore, and that's why I replaced both boards. Haven't had a single problem since (fingers crossed). By the way, here is some more information on the subject:

http://www.actionpinball.com/tech/tz_prox.htm

Very handy info, thanks gweempose.

well bazzman you made me fix mine too. This issue has plagued me since I owned TZ. After answering you yesterday I started to think about mine. I had a piece of electrical tape holding the plug in place....It's been working but I decided to just solder the wires to the boards...I did that tonight.

So Thanks. I hope you get yours fixed as well.

Nice work, Bazzman! That is the fix described in this thread. Hope it fixes your sensing issues.

The wire would not be the issue,
It is just one individual copper wires inside the red cable.

Unless it shorts to the black??

Nice pic by the way.

Cheers

I noticed a small break in the red wire where is soldered to the board (see pic)would this be the problem?

Oh, are you saying that the wires were already soldered to your boards? If so, the repair was already done by someone. There is supposed to be Molex connectors on the wires and boards originally. If you see a cracked solder joint on either connection on either board, then you need to re-flow the solder with your soldering iron. A cracked solder joint will for sure cause the problem you are having.

What's interesting is that those aren't the original boards. The OEM boards look like this:

tz_prox.jpg

I've never actually seen those particular boards before, but based on the fact that the main PCB says "THE LIZ" on it, I'm guessing they were made by Pinball Lizard. Sadly, he closed up shop a while back. I know his TZ clock board was quite popular.

POWERBALL!!!!!

Congrats Bazzman. It's a strange type of fix, but it seems to work for some of us.

Here's a different Powerball story. I picked up my TZ about 3 weeks ago from a guy who owned it for about 15 years. He was not really into pins, but he wanted one in his gameroom. When I showed up to get the game, I opened up the coindoor to see if there was anything loose inside that might roll around when we started moving it. I pulled out the head bolts, (never installed), two pinballs and a Powerball! I immediately thought that he put another brand new Powerball in the game, but he says, "What's that?" I say, it's the Powerball a unique feature of TZ. He goes, "Oh, I never saw that before!" They played the game for 15 years with no Powerball in the game!

Shock_me that is funny. I picked up a TZ last week it had no power ball, it had 6 steel balls. Not sure why.

Thats odd probably the previous owner didnt like the powerball or it is
not being detected.Just replace one ball with a powerball and see if it is being detected
during gameplay.If not this thread pretty much covered the issues.

Yes,All flashers should light up.Are they all not working?

They work during gameplay.... but not in test? Is this reproducible...?

You have just crossed over into... the Twilight Zone

It is actually called a proximity sensor and when the game breaks in the ball has a tendency to smack it as the ball seats itself in the trough.
You want to put a ball in the trough and adjust it so it is centered on the ball and back from it about 1/16".
The connectors can be problematic and the best way to fix it is to hard wire the wires to the boards.
Solder them to the boards and not the pins in case you want to replace the loom at a later date.
This fixes most of them unless the ball has bashed the sensor and broken it.
If that is the case the Pinpoint boards Gweem posted work well.

Interlock switch on the coindoor, put it in test and close the door or hold in the switch.

Two years later and still solving problems. Worked like a charm!!!

Ugh, okay, worked like a charm for a little bit. Darn it. Now the red light is on 100% of the time, ball or no ball. I pulled the board off to take a look at cannot get the light to turn off no matter what I do, so I'm thinking there's something wrong with either the sensor itself of the board. Any thoughts?

Whoa, weird. I just checked out the OEM pics posted by gweempose and I don't have those green and white cords soldered onto the bottom of the board. I've just got the red and black lines that plug in.

...and that damn red light is still on 24x7, even if i unplug the sensor board entirely

if you don't have that set of wires on the driver board in the lower section of the picture that is your problem running man... those are the wires that send the signal to the game. Should be a connector with 4 wires...

Neither do I and I am having the same issue... the red light stays on 100% of the time. I dont however see any evidence that there was any green and white wires soldered to the sensor board at any time.

What's weird is that those wires, if ripped off accidentally somehow, would have to be *somewhere* under the playfield. I looked around and don't see them anywhere. How weird!

Oh well, I ordered a replacement kit for 60 bucks. If I install that and it doesn't fix the problem them I know I'm hosed.

Those wires are "hacks" added afterward. Good hacks...
That's the way I fix them too, but I use the original wires, and solder them directly to the connector solder pads.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

Thank you for posting the close-up pictures of the trough proximity sensor, Bazzman. They were a huge help and kept me from having to purchase a new unit? My TZ Is running perfectly with no errors--awesome!

Just had my Twilight Zone Trough proximity switch 26 get stuck closed.
I have already replaced the boards with the red Big Daddy Pinpoint board pictured above.
It worked great for about 8 months now but suddenly I can't make it turn off.
I have tried adjusting the little copper screw in the blue part of the larger board but it just spins in place. Thought maybe it was a pot adjustment for the sensor. Guess not.
Any ideas what might be causing it to stay activated. I have all new wiring and new boards and can't imagine what has gone wrong.

Has the board itself shifted. Check to see if it has come loose.

Yes. it is attached very tight.
The red light stays on if there is a metal ball in the trough or even if no balls are in the trough.

Noted!

I had the error 26 and the powerball wasn’t being sensed in the trough. I took it apart and checkEd it all out and cleaned it and it was sensing it again. Now it’s seems to be sensing more than just the powerball? It will say powerball and kick out the powerball but the multiball will stop when a ball drains into the trough and there will still be a multiball going. It’s now sending everything out of whack. I’m not sure what to do from here. Any ideas?

Did you Reseat the connector on the small board under the playfield?The one that has a small connector with 2 wires.

I had this problem as well, for me it was the J1 connector
L1 Proximity Sensor Board A-16534
J1-1 Black, Ground from J118-3
J1-2 Gray-Yellow, +12VDC from J118-2
J1-3 Green-Red from J206-2
J1-4 White-Blue fromJ208-7
I removed the IDC connector and put them in to a Trifurcon pin and housing. I've had no issues (with that at least) since. It's a bit tough since these wires are looped through the connector, but if you can twist them tight enough you can squeeze them into the .100 pins with only the wire being crimped.
I went through 3 sets of boards before I figured out it wasn't the real issue.