After a few hours of play, my TZ gets some WEAK flippers. It's to the point that hitting ramps is tough, and the upper left flipper cannot even make the piano shot. Of course, I don't regularly play my TZ for 3 hours, I only notice this problem when hosting a pinball league meetup. This makes diagnosing/fixing quite tough.

From reading Clay's guides and RGP I thought it might be dirty optos or a bad fliptronics chip. Supposedly they can cause small pulses to the flipper coils that heat them up over time. In order to test this theory, I left my game on in test mode for a few hours (display detached to prevent image burn), but the coils did not heat up.

All the flippers have some room to move up/down, so it's not the link binding. The lower flippers were rebuilt and new coils were installed at the lower right and upper left flippers.

Could this be a transistor problem? Thoughts on how to pin down the problem?

I am no expert but I would check my voltages to the coil at the beginning and when it is getting weak. To me it sounds like you are not getting the full power after a while.  

my two cents

take care

Good idea, but now I have to play TZ for 3 hours straight to test it out

There's a burn-in mode that can do it for me right?

Quoted from jonny_eh

Good idea, but now I have to play TZ for 3 hours straight to test it out

There's a burn-in mode that can do it for me right?

Sorry I don't know about that but simply leaving the machine on should do it since your transformer would still have to warm up etc.  I suspect this is where (power conversion) your problem might be coming.  I don't know enough about the DMD machines to be able to tell you more but my past experience with electricity etc.  pointed me to this check first. This way you will go in another direction and leave your flippers alone.

take care

make sure your EOS switches are properly adjusted. if they are not, the coils will get hotter and hotter, resulting in sluggish performance.

Quoted from Mrhide

make sure your EOS switches are properly adjusted. if they are not, the coils will get hotter and hotter, resulting in sluggish performance.

on that note, clean the EOS with a business card even it they are adjusted correct.

The EOS are fine, I checked them. But shouldn't they not matter since it's a fliptronics game?

Check the flipper optos, if they are bad the flippers will be weak and inconsistent.  Optos start to fail over time and the easy way to check is to put it in Switch Edges Test and look for them blinking erratically. They might not act up right away. The other way to tell is hold the flipper half way and push the button, you should feel a quick pulse. All the flippers should feel the same. If you feel one has a slight vibration it is likely the opto. I remove the bad optos and put leaf switches in there place and this eliminates the problem from coming back. I hope this helps.

Good luck

Quoted from workingpins

Check the flipper optos, if they are bad the flippers will be weak and inconsistent.  Optos start to fail over time and the easy way to check is to put it in Switch Edges Test and look for them blinking erratically. They might not act up right away. The other way to tell is hold the flipper half way and push the button, you should feel a quick pulse. All the flippers should feel the same. If you feel one has a slight vibration it is likely the opto. I remove the bad optos and put leaf switches in there place and this eliminates the problem from coming back. I hope this helps.

Good luck

I put it in switch test but didn't see any blinking. I'll try your other suggestions when I get back home.

Also one of the other problems that go with the bad optos, can be the flipper staying up for a half a second after releasing the button. The coil stop gets magnetized from the constant pulsing of the high power.

Quoted from workingpins

Check the flipper optos, if they are bad the flippers will be weak and inconsistent.  Optos start to fail over time and the easy way to check is to put it in Switch Edges Test and look for them blinking erratically. They might not act up right away. The other way to tell is hold the flipper half way and push the button, you should feel a quick pulse. All the flippers should feel the same. If you feel one has a slight vibration it is likely the opto. I remove the bad optos and put leaf switches in there place and this eliminates the problem from coming back. I hope this helps.

Good luck

Optos tested ok Anything else I can try?

Are both left and right flippers weakened??

My first suggestion: I agree you need to find a time where the flippers are weakened again and test the voltage fed to the flipper coils at that time. If it is lower, you need to check the power section on the WPC driver board.

When you press a flipper button, you close a relay which completes the circuit to ground. The other possibility might be the relay itself and a degrading contact possibly due to temperature.

For the optos, I would check the voltage signal downstream from the opto switch in the weakened condition. I doubt it is the cause though!
Other possibilities within the opto board, fliptronic board.

Last step, go on RGP and ask there. Maybe Clay will help you out (if you're lucky).