Quoted from yoshootme:

I have a very good example of one on the east coast (NJ) that I just put up for $6,200. zero fade. plays perfectly. certified board, if that means anything to anyone, new rottendog clock board, no mods, no bites yet. a similar one, as far as condition, but with some fade just sold for $5,500 in about 2 days. so my guess is somewhere in between those numbers depending upon condition.

Quoted from Fanatic:

Here are some articles which may help:
http://pinside.com/pinball/forum/topic/tz-clock-broken
http://pinside.com/pinball/forum/topic/tz-clock-not-working
http://pinside.com/pinball/forum/topic/tz-clock-is-broken
I hope this helps guide you to a solution.

Quoted from Manny65:

Methos The ball sensor pictured above is the one that is working one your machine - it'll sense a metal ball coming from the gumball or camera or deadend, so when the ball triggers the microswitch in the trough but the above sensor doesn't sense a metal ball then it is the Powerball.
Switch 26 (where your issue is) is made up of 2 small PCBs, one is located at the right-hand end of the shooter trough. This switch is a common issue with TZ. There are improved replacement boards available or you can repair/improve the original if you have the skills