Another low +5v power issue, but I think different than others I've seen posted here and in the STTNG thread. Based on my diagnosis so far, I'm thinking something on the CPU board may be drawing down the 5v, see if you agree or disagree. About to pull the CPU board to install updated ROMs and a coin cell holder to replace remote battery holder, decided to also remove the Kahr board (installed a year ago or so, was preparing for a party when a reset happened) and analyze the +5v situation for a proper fix.

Stock TZ. Z connector removed properly a couple of years ago. No mods other than gumball flashers on playfield door panel. TZ has been in my home for over 20 years and sees very little use, so little "on" time. Mounting screws on driver board are snug. 124v at TZ's service outlet. C5 was replaced some time many years ago, not sure about BR2. Nothing else is powered up on TZ's branch circuit. Tests were run with a game started, but not actively being played.

Before removing Kahr board, 5.05v at Game ROM pin 32, 4.84v at TP2 on driver board.
After removing Kahr board, 4.80v at Game ROM pin 32, 4.81v at TP2 on driver board. Below 4.92v, so risky.
After reseating J101 4.84v at TP2, gain of only 0.03v.
After reseating J114, 4.81v at Game ROM pin 32, gain of only 0.01v.
After reseating plugs at transformer, no change in TP2 voltage.
Remove J114, J116, J117 and J118, 4.97v at TP2, gain of 0.13v. Seems significant.
Replace J114, TP2 drops back to 4.85v.
Replace J116, no change in TP2 voltage.
Replace J117, no change in TP2 voltage.
Replace J118, no change in TP2 voltage.
With all connectors in place, tested BR2 and associated cap as per Pinwiki instructions using a test lead clipped onto the top left lead (positive) of BR2. DC volts = 10.07, AC volts = 237mv.
Did not examine the Thermistor, haven't pulled any of the boards yet (so haven't checked for poor solder joints) but the boards look unhacked.

The standout item to me is the drop in +5v reading at TP2 from 4.97v with J114 disconnected to 4.85v with J114 reconnected. So, something on the CPU board is pulling down the +5v?

I do have a PSU5 on hand so I could easily replace the LM323K when I have the driver board out for inspection, and was thinking of doing that anyway to reduce current draw / heat.

How would you proceed next?

Those that do repair work on these boards - is a drop from 4.97v to 4.85v a normal amount of drop to see at TP2 when connecting J114?

Couldn't get the link from your reply, but I did get it by going back to your earlier post, thanks! Chased the link. No connector burn at J101 for me, and C5 has been previously replaced. My voltage is a bit lower at TP2 than what he had, only 4.85v. Well, I think I have checked most everything I can check without pulling boards, so it is time to pull the driver board. I'll check the relevant header pin solder joints and reconfirm no connector burn. I think I'll install the PSU5 to replace the LM323K and see if that helps, but may throw in another driver board first to see if it exhibits the same symptoms in the game.

Posting to "close the loop". I pulled the CPU board. All clean on there. Removed the battery holder and installed a coin cell holder, replaced the ROM with 9.4CH. Noticed I had the blue Phillips cap at C31, so I replaced that while I had the board out. Didn't have an axial cap on hand, so instead I used a 100uf 100v radial cap I had from GPE. Reinstalled the CPU. No resulting change in the 5v readings at pin 32 on the game ROM vs. TP2 on the power driver board.

Pulled the driver board and examined it. No cracked solder joints at the headers or at F113. Solder on the LM323K looked good. BR2 and C5 already tested good a few days ago per PinWiki WPC section 6.16.12. Header pins and connectors look good, as expected given the low "on hours" for this game. So, I decided to remove the LM323K and install a PSU5. A simple job, although the PSU5 units I just received in the mail recently differ slightly in appearance from those pictures I have seen posted on Pinside. Notice there are tiny labels screened on the PSU5 for the 2 pins, one says "in" and one says "out". Orient the PSU5 so the "in" pin connects to the back of the driver board trace that goes to BR2 / C5. And as others have suggested, install the PSU5 to the board with the mounting screws first (discard the old nuts and instead use replacement #6 nuts with split washers to avoid a short circuit, and in my case solder had been worked into the head of the screws making it impossible to use a screwdriver on them, so those screws were replaced with new), then go ahead and solder the PSU5 to the board. I now have 5.07v on pin 32 of the game ROM, so all is good! Trimmer pot on the PSU5 can be used to carefully adjust the 5v to where you want it, best done with J114 disconnected for safety reasons.

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Next up is the long delayed installation of a Borygard Special Edition clock board!

I'm finally ready to install one of Ingo's "Borygard special edition" clock boards. Bought years ago, but it is a 1.9 Final version. I downloaded the install instructions from Ingo's website here: https://www.german-pinball-modular.de/tz-clock-instruction-english.html. I have run into something interesting, and maybe this helps explain why my clock has never worked correctly since the day I bought the machine over 17 years ago. I'm at installation step 1, lining up the clock. I can get either the hour hand to the 12 position, or the minute hand to the 12 position, but not both. When the hour hand is at the 12 position, the minute hand is not even close. See these pics.

Suggestions for how to proceed with step #1 of the installation instructions, aligning the clock hands for disassembly? Do I go with the minute hand at the 12 position and the hour hand at the 11+ position? Or do I go with the hour hand at the 12 position and the minute hand at the 4 position? I don't want to damage anything during disassembly.
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Well, this is going to be more work than I had hoped. Spent some time searching. Saw the recommendation to use Superlube on the gears. I also saw a recommendation for Shimano premium grease which I think I still have from my bicycling days. Saw the recommendation to not use any grease at all. Ok, I can sort that out.

The big issue is aligning the gears. No idea if my game was wrong from the factory, or if prior owner serviced the clock and messed it up, but I'm a bit nervous about taking the gearing apart. So I see the 2 pages in the TZ manual that discuss aligning the clock gears. Yikes!! In my situation, can I make things any better if I align the clock somehow before I start? For example, in clock test I could stop the clock when the test thinks 12 has been reached, or something....

All tips accepted before I dive in! Bonus points if someone has a nice picture of what the properly assembled gearing looks like before the Output gear is installed.
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I sincerely believe that Coyote's advice is well intentioned!

I think I'll bring the clock to the bench to work on this. Question: while on the bench, is it possible to test after rebuilding without reinstalling the clock in the machine? I do have a portable DC power supply.

Please, sincere replies only!

Yeah, that was my plan too when I was just installing the replacement clock board, but now that I know I need to also disassemble the gears and then reassemble them, I don't think I want to try doing that on the playfield of the machine.

As always, I'm amazed by the support provided here. You all give me the confidence to dive in and get this done rather than pushing it to the back of the line.

I notice that I have a bottle of Zoom oil, great stuff for spinners. Ok to use Zoom sparingly on the clock gears and shafts?

Give Ingo a shout, I bet he gets you taken care of right.