I´m having the problem that on my completely shopped Corvette (with CPR repro playfield) the ball almost never stays in the engine but more or less immediately drops into the lock. I´ve been on and off analyzing the problem but couldn´t really identify any problem with the gate itself until I noticed that the gate closes with a slight delay after the ball passes the first opto on the ramp. I wondered how long that delay is and because I couldn´t figure out a way to measure that with an oscilloscope I tried recording the behaviour with a high speed camera. Although my little movie was very dark and fuzzy I could still see that the delay was almost half a second until the gate drops down. If the ball takes a straight way from the bat up the ramp, against the back gate and back it looked to me that it´s back at the front gate well before that half second is over. So it drops into the lock before it can be blocked by the front gate to stay in the engine. I figured that this might be due to the higher speed of the ball on these 2k playfields.
But because my video was so fuzzy I wanted to make sure that my impression is correct and the delay is really that long. So I used my PinLightShield and some Arduino code to measure the time between the first opto and the second one (to determine the ball speed) and the time between the first opto and the moment the coil of the gate gets activated. You can see my setup here:

P1050521 (resized).JPG

The results are pretty consistent with what I could see on my video. The delay of the coil activation is always somewhere between 350 and 400 ms.
The time the ball takes between opto1 and opto2 is 22 ms on a solid shot that didn´t bounce anywhere before going up the ramp. The distance the ball has to cover from opto1 to the back gate and back to the front gate is about 8 times the distance between opto1 and opto2, so it would take the ball 176 ms (8 x 22) to travel that distance. So even if it gets slowed down a bit more after passing opto2 and hitting the back gate there´s still plenty of time to sneak under the front gate before that actually comes down.

This raises the following questions, which I hope some of you can shed some light on:

1.) Is that delay of almost half a second normal?

2.) If yes, what could be done about it? Tweak the code (I´ve never done that)? Put some foam on the back gate to slow down the ball?

3.) Has anybody else seen this behaviour on Corvettes with a new 2k playfield?

All parts on that coil are new and there´s no mechanical issue. With my setup I´m actually measuring the moment when the driver transistor opens the path to ground, so mechanical issues wouldn´t be registered.
One strange thing I´ve noticed is that this particular coil gives kind of a buzzing sound when activated.

Hi Brijam,
sorry for responding so late but I was on vacation.

The delay I was measuring is really the software delay, because my trigger is the moment the driver transistor shorts the coil to ground. Any mechanical delay would be on top of that.

But I just noticed that I´m on v1 of the software while there are updated versions which seem to address also issues with the lower rev gate.
I just burned a new EPROM and will measure the delay again with the new version. I´ll report the results asap.

What version is your Corvette on?
Herbert

Installed the new EPROMs (v2.1) over the weekend. The delay in the code has been cut in half so is now roughly 200ms. It´s still too long for really fast shots up the ramp on this clearcoated pf but I´d say in >90% the lower gate catches the ball before it can fall into the lock.
If I´d only known that the solution is as easy as installing a new software version.......

Playing my Corvette is now a whole lot more fun than it was before!