Have you gone into test mode for the T-Rex to see if you can make him turn there? When you say intermittent, do you mean that some days/games he will turn back and forth normally. Or that when he does turn he will do so in a kind of start and stop fashion?

If it is the start and stop one, then it sounds to me like there is no connection issue. Sporadic movement is the normal symptom of a bad gearbox. Google the T-rex motors and you will get plenty of information on how many problems there are with them. Essentially your gears are likely shot. Most people with this problem just turn of the left right movement because as long as the T-rex eats the ball, they are happy. The motor can be pricey.

If you do replace the motor, make sure you update your roms, as the newer code puts less wear on the gears.

How? Move T-Rex less during gameplay?

If he is moving but choppy movements it is the motor. Had that same problem the wire going to the motor was broken rt ar the wire coil.

Nope. It is uses rapid pulses to the motor instead of full power on and off. It is supposed to cause less wear on the gears.

Lots of topics on it out there.

is the left right motion turned off in the menus???

And if it's not, it probably should be.

The left and right thing is kinda clunky and not exactly impressive. (In fact, I think the game moves along a lot better without the T-Rex taking the time to find his center before grabbing the ball.)

The star of the whole show is that ball-chomping action, and if it does that, then bravo.

What was the solution?

having a few issues with my T Rex, moving sideways very slowing or nothing, removed motor & bench tested it @ 6v seems ok, motor mounted in gearbox about 4.5v, thinking the gearbox is messed up, sometimes the gearbox jams up,

thinking new gear box & motor & new roms just to be sure?

I worked on a JP that had this problem. The l/r movement was so sluggish, that the trex could not find his center before the CPU would disable the l/r movement.

To correct the problem, I added full-wave rectification for the l/r motor, which greatly improved the trex l/r movement. If you look at the circuit board above, you'll see 3 diodes. 2 are for full wave rectification of the shaker motor, and 1 is for half wave rectification of the trex l/r motor. Since the AC feed for this comes from a center-tapped part of the transformer (see manual pg. 46), you can easily add one diode and one fuse to the circuit board above and feed a full wave rectified signal to the l/r motor (see page 49, left side). If you want to change it back to half wave rectified (original) later, you simply remove one of two the fuses for the l/r motor.

fullwave.gif

jp_fullWave_LR (resized).png

Are you saying T-Rex moves very slow with CPU ROM 5.01 due to the fact that PWM is performed on the motor AND power going to the motor is only partially rectified?

yes, same happened to me, did the modification for full wave rectification and now its ok, pwm to slow down the motor does not seem to me a good idea for the gearbox as the motor is allways in stop and go process

I’m looking to add full wave rectification for the left right motor and I want to double check so I don’t mess anything up.
Am I running a wire with fuse and diode from the gry-grn wire on J1 to the gry-blu wire on J3?

1E3C48FA-5B6B-4A72-91F6-8EF63BB1898E (resized).pngA7B4C1B9-A9B8-44D0-B539-3A00B3945589 (resized).jpeg

2B031FC5-BB44-42E7-89B9-4D61AF7204CB (resized).jpeg

Jumper from gry-grn wire to new fuse in series with non-banded end of new diode...then banded end of new diode connected to banded end of diode that is not already connected to another diode (D1 it looks like).

The D1 diode is the only trace going to J3 so I tied into the gry-blu wire.
It works great!!
T-Rex is much smoother, eats the ball every time, and twice as fast going left/right!

452F267E-4F45-4200-A122-26F07EF86B85 (resized).jpeg