In clock tests - are all the optos working ?

LTG : )

If it on;y goes in one direction, then either:
1. You lost a driver (or pre-driver) transistor on your power driver board, or,
2. Your Motor control board (mounted under the playfield) is bad and needs to be fixed.

I’ve had this issue before. Check the small right board in the backbox. You have a blown transistor there

I have this same problem on my game. The clock immediately goes backwards on startup.
I replaced the underplay field motor control board and didn't fix the issue.
My power driver board recently got checked by Coinop-Cauldron. I suppose a transistor could still have gone bad. Is their an easy check for this before I send in my board (again)?

thanks

If your clock starts moving and keeps moving when power is first applied, it could be a couple of things.

The motor driver chip on the DC Motor Control Assembly A-16120 could be shorted.

The capacitor on this board C3, 100uf, probably 25v could be bad, causing this board to have unreliable power. I mention this because Opto boards with a similar capacitor have had a lot of failures lately due to the 100uf capacitor going bad.

Other components on this board may have failed, like the optoisolators.

Truth be told, the motor driver chip or the opto isolators are unlikely, the capacitor is somewhat likely.

This board is controlled by the 8 driver PCB assembly A-16100 (I think this is in the backbox).

It could be a shorted transistor on this board, Q9 or Q10, or their pre-drivers Q3 or Q4. Possibly.

However, this board is controlled by a ribbon cable! And ribbon cables can be problematic. This ribbon cable stretches from J1 on the 8 driver PCB Assembly A-16100 to the CPU on J104. If this ribbon cable isn't making good connection it could definitely be the problem. Re-seat both sides of this ribbon cable.

Now, if your clock stays inert until the game is booted, and then it starts spinning, I would look to the clock test. Make sure that the optos are all activating in the clock test mode.

Let us know what you find.

Also, while I understand that it may be very challenging to find a local pinball service technician, you might want to get a repair person to your house. There are multiple boards, multiple connections here. Look in your manual on page 3-12, 3-13, and 3-22.

A skilled pinball technician can quickly determine where the problem is, and will likely have the parts to fix it. (If it isn't the motor control chip, that's a rare failure!)

If you need to send boards out, you are going to be unplugging quite a lot of things, and removing a lot of boards. Take pictures of each step!

Good luck!

10-6-23 I posted here that the opto failure was rare, but this seems to be becoming more common. U1 optoisolator has been the problem on several TZ clocks that I've repaired lately. The symptom is that the clock starts running as soon as the power is applied to the game and doesn't stop.

thanks for the heavy detailed reply. I'll start the process of looking into this.

Ben.

Update:
I’ve replaced two boards so far.. the driver board in the back box and under the playfield.
The clock behavior hasn’t changed still moving backwards immediately upon startup.

I reset the ribbon cables also

Then that leaves the wires. With the game turned off, is the driver wire for sol #42 (Blu-White) shorted to ground?

Thanks for replying. I'm not sure how to test this. How do I test "shorted to ground"?
thanks

Grab a meter. One probe on ground. The other probe on blue/white wire.

You tube has lots of short video to use a meter and check things like this.

LTG : )

figured I'd finish this post with my solution. I had a tech visit who found the problem was a faulty driver board. a-160120 I believe. lower right under the play field in the back corner.

FWIW - this post is excellent. Made it super easy to isolate the fault to the motor control board and then to the specific component on the bench a 4N25, a $0.28 part, by just pulling connectors.

IMG_1236 (resized).jpeg

IMG_1237 (resized).jpeg