(Topic ID: 256317)


By Mikemolang

84 days ago

Topic Stats

  • 11 posts
  • 6 Pinsiders participating
  • Latest reply 82 days ago by PinballManiac40
  • No one calls this topic a favorite


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#1 84 days ago

Hi all,

PROBLEM: My Tommy DMD only rapidly flashes:

FEBRUARY 15, 1994

...but otherwise the game plays fine. Ideas?

Game was working fine.
I installed an LED kit. (Lots of jostling to playfield, wires, etc.)
Started machine, but the VUK was dead. (Fixed - Replaced blown fuse)
Started machine, DMD was working. But after a minute (with a ball in play on the playfield) the DMD went into this mode.
Power cycled, let sit overnight, but still no good, although the game plays fine otherwise.

I need to check the fat bundles of wires near the rear of the machine (especially the one on the left) because while troubleshooting this problem I noticed some abuse and a couple loops of wire pulled out / poking out. Might have a shorted or broken wire.

My guess is that the DMD controller is not getting a signal. But isif there is some other likely reason... Any pointers appreciated.


IMG_7061 (resized).jpg

#2 84 days ago

Reseat all the ribbon cables at all ends.

#3 84 days ago

Is the power supply board all original? Lots of caps on that board, if original, are prone to failure at this point which weakens the 5 volt logic line and can cause a boot cycle such as this.

#4 84 days ago

Also confirm that there is no battery corrosion

#5 84 days ago

A logic probe (LP) would be a good tool to invest in. You can pick these up for around $20USD plus postage... You can use the LP to verify there is activity on data lines to see if there is some sort of information flowing at the display driver board.

Your problem sounds like an issue with communications between the MPU and the Display Driver Board. You say the game works normally but the display is only cycling the Reset state. However there is no Watchdog Reset function on the Display Driver board - and here one would want the logic probe to check that:

A) you have a stable High on the output of U15A (pin 3) and after that that pin 37 of U9 (68B09E - CPU) is High. this indicates that RESET is stable and not active.

B) if both circuits in A) are stable and High then see (with the LP) if you are getting data (blinking LP indicators) on pins 11 through 18 (incoming data lines) of U17, and also pins 11 through 14 of U19 (Stat0 through Stat3). All should be busy if the MPU is running happily.

C) if any issues with logic line inputs in B), then check on the MPU board for the source logic lines...

Hope this helps, but you need basic electronic tools about now to speed up the process and to have a rough idea of what is going on in your game...

John :-#)#

#6 83 days ago

@flippers_com - Thank you! Exactly what I am looking for. No problem with the basic tools and skills. I have a DVM, a DLP, and an LCD oscilloscope at my disposal. I expect to work on this over Thanksgiving weekend, and I will report back.

All others - Thank you.
The batteries are not leaking, and were replaced 2 weeks ago.
The electrolytic caps all appear to be original, so she deserves a re-cap, for sure. (Side note: Suggestions on a cap kit for TOMMY?)
Will push and prod things, and check voltages, as suggested.

Thanks all,

#7 82 days ago

flippers_com - OK, I cannot find the reference designators for the IC's on the PCB, nor in the manual. Suggestions?


#8 82 days ago

What do the leds on the MPU show? They have a startup pattern.
This will give you some ideas.


Quoted from Mikemolang:

flippers_com - OK, I cannot find the reference designators for the IC's on the PCB, nor in the manual. Suggestions?

#9 82 days ago
Quoted from Mikemolang:

flippers_com - OK, I cannot find the reference designators for the IC's on the PCB, nor in the manual. Suggestions?

These reference pins are on the Dot Matrix Controller (#520-5055-00), pg 98 of the Tommy manual I downloaded from IPBD...

John :-#)#

#10 82 days ago

In the end it was PinballManiac40 who was quickest to the solution. A press of the ribbon cable solved everything.

Still, flippers_com , thank you. I was looking on the CPU schematic because I misunderstood what you meant when you mentioned the CPU above. Now I get it.

Thanks all!

#11 82 days ago

Awesome. Play ball !!

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