I have a TZ that I bought about half a year ago but never used. I finally got it 'installed' in the house and powered up, only to have an intermittent issue with the machine going dead then going back to the 'start screen'. This would happen with no relation to flipper use or other action but it was happening a lot....it was hard to play a full 3 ball game without a drop-out.
I looked online for guidance and checked various items but found nothing wrong. I even powered the machine off a CVT to try to eliminate any voltage supply issues.
Finally, I looked in the 'power box' where the On/Off switch is located. I was surprised and pleased to see a lot of smoke residue and the varistor that goes between the legs of the EMI filter was split open. The thermistor was also not-too-great looking. I went ahead and replaced the EMI filter and the varistor and thermistor and the machine is working great.
I'm posting this in case it helps someone else....why didn't I check the power box to start with? This machine is 'minty' - home use only since new and clean enough to eat off .... from looking at the outside of the box you'd never guess the inside was so smoky. So much for outward appearances!