Have you made any progress with this?

Do you have a device to measure frequency?
In terms of the attract mode slowness, make sure the following signals are in spec:
Pin 18 of U10 should have a 120Hz signal (Zero Crossing Interrupt)
Pin 40 of U11 should have a 317Hz - 320Hz signal (Display Interrupt)

It's unlikely but possible that the solenoid Q9 transistor repeatedly activating could be related to the slowness issue you've got with timers being out of whack.
What game are you testing it in?

Have you tried another 6800 CPU at U9?

You'll need to leave the board in the game to properly measure the Zero Crossing detection circuit because it's derived from the unregulated 43V DC solenoid supply line.

Ok, solenoid transistor Q9 continually activating tells me the MPU board is sensing the left side kicker switch as being stuck on. It's trying to eject a "stuck ball" from the kicker.

I was helping a fellow pinsider repair a battery corroded board 6 months ago - he got the board booting to attract mode but it would stop at that point (displays working, but no lamp animation/switch response). Turned out to be his CPU causing it, which is why I mentioned it.

Ok, if you hook up connector J3 to the MPU board, can you get into test mode?

No worries.

I'd be interested in knowing if the lamp/display tests run at normal speed.
Also if you can get to switch test mode, disconnect J2 and J3 from the MPU board live and see if the MPU board thinks any switches are closed.

What's happening on the displays?

Check the CPU socket as jj44114 mentioned.

If you set all the 32 dip switches to OFF, does the game start in factory test mode?

Might be time to post some very clear pictures of the front and back of the board.

Try adding/melting a drop of new solder on each pin first. It makes it easier for the solder sucker to effectively melt the old solder for removal.

To be honest, looking at your board pictures I rather doubt that U9 socket was your issue.
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I think we need to revisit this. When I check in emulation with the kicker switch stuck closed, the game runs dead slow in attract mode and activates the Q9 transistor for the kicker solenoid repeatedly once a second which sounds like your original issue.

I can see someone has replaced diode CR41 on the MPU board which is on the switch return line signal that the kicker switch lives in the switch matrix.

Repair those two lifted traces and install a new U9 socket then put the original 6800 CPU back in.
I don't know if you saw this thread below but you're likely to have similar board issues. We should do some resistance measurements on the switch return signals on the MPU board.
https://pinside.com/pinball/forum/topic/tilt-immediately-at-game-start-but-no-stuck-switches
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With the MPU board on the bench i.e. disconnected from game, set your multimeter in resistance mode (at the 200k ohms scale if your meter isn't auto-scaling) and measure the resistance between:

a) J2 pin 8 and J2 pin 9 (i.e. one meter lead on pin 8, the other meter lead on pin 9)
b) J2 pin 11 and J2 pin 12
c) J2 pin 14 and J2 pin 15

Now measure the resistance between these signals on the 6821 PIA chip at U10 between:
d) pin 10 and pin 11 (i.e. one meter lead on pin 10, the other meter lead on pin 11)
e) pin 13 and pin 14
f) pin 16 and pin 17

Report all the readings.
For reference, two of my boards on the bench measure around 95k-100k ohms at all these locations.

Try and report the readings requested on post #24 above. You can do the readings before repairing the U9 socket since U9 is not part of that circuit. I need to head out so we can follow up later/tomorrow.

Don't change the socket yet. Report the resistance readings first.

Oops, sorry I was in a rush.
The repair looks good. I presume you have solid connection between the top and bottom traces at those two pin holes at the U9 socket where the traces lifted?

The switch return line shown on the schematic as "I1" (where the kicker switch signal comes back on) is the PB1 signal (pin 11) of U10 and it goes to a 56K resistor (R45) which pulls the signal low. Your original symptoms and very high resistance readings at pins 10 to 11 on U10 tell me there is an open circuit on this PB1 signal to that resistor or the resistor itself is open circuit.

See the picture below showing the location of this resistor. With your meter on resistance mode, do you read 56k ohm across that resistor?
Pin 11 of U10 goes to the left side of that R45 resistor. Do you measure an open or short circuit between these two points? If it's open, follow the traces on top and bottom of the board between these locations to try and work out where it's open circuit.

HotHand_MPU_Front1.jpg

Great stuff!

Is the test switch on the coin door working now?
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Since the resistor couldn't pull the signal low, the open circuit signal must have been closer to or in the high logic threshold of the PIA sense circuit. It lead to all switches on that row being read as active which the kicker continually reactivating was the clue.

Trivia: Hot Hand has a secondary switch location within the matrix that spots the "Ace", but no switch on the playfield is assigned to it. Makes me wonder if that white standup target next to the spinner was originally put there to spot the Ace but was deemed too easy...

Actually there's two unused Ace switches - the two unmarked/unused switches between the "Jack" and "Ten" on row I5 both spot the Ace.

This is rather unusual because the audits are stored in the same locations.. Even a lot of the audit locations are common between Bally and Stern MPU-100 games. I'm not sure about the later Bally-35 games and think Stern may have changed things on their MPU-200 games.

I'm not sure about the later Bally-35 games (Black Pyramid might have changed locations). Stern changed audit locations on their MPU-200 games.

Same ROMs on a Stern MPU-100 or Bally-35 board should store the audits in the same location though - addressing to the U8 RAM is the same on both boards.