(Topic ID: 298307)

Gottlieb Rock - 10,000 lamps not alternating

By jsm174

2 years ago

Topic Stats

  • 5 posts
  • 2 Pinsiders participating
  • Latest reply 2 years ago by Quench
  • Topic is favorited by 1 Pinsider


Linked Games

  • Rock Gottlieb, 1985

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#1 2 years ago

Hello all,

I've been working on fixing up a Gottlieb Rock for a friend for the past month. The machine was in rough shape. When I got it, a bunch of fuses were blown, the outhole, 4 and 5 bank drop target solenoids were dead, and the knocker was stuck on, the game would lock up, etc.

I've worked through all those issues -- rebuilt a lot of the driver board and replaced Z30 on the control board.

Everything is working well now except for the 10,000 lamps - L47 and L51. During attract mode (and gameplay) these lights should alternate. I verified on a real game at Pinfest last week.

The behavior I'm seeing is strange. Sometimes when I turn on the game L47 will be on, other times L51 will be on. During attract mode, the light will look like it wants to alternate (ie, just a hint of dimming) but is on solid. Ocassionally during game play, (very rarely) the lamps will toggle.

Using the info at PinWiki, I tested Q48 and Q52, R48 and R52, and these are within the tolerances.

Using a logic probe, here is what I'm seeing on Z12 during the lamp test:

- Q1, -Q1 L44, L48 work as expected
- Q2, -Q2 L45, L49 work as expected
- Q3, -Q3 L46, L50 work as expected
- Q4, -Q4 L47, L51 do not toggle, L47 is high, while L51 is low
- D1, D2, D3, D4 work as expected. D4 does toggle (as I would expect) in the lamp test for Lamp 47.

I was all set to replace Z12 74175N, until I followed the test at: https://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit

All the values are within the tolerances, and match Z11, etc.

Anyone ever see this issue before?

#2 2 years ago

Using your meter on the output pins of the chip tests its output transistors. While this can identify faults with the chip, good readings don't tell you what's happening upstream within the chip.

Since both the 4Q and /4Q outputs are struggling to change, it says the predrive transistor circuit in the chip for flip-flop 4 is likely suspect.

In your shoes I would still replace the chip.


#3 2 years ago
Quoted from Quench:

Since both the 4Q and /4Q outputs are struggling to change, it says the predrive transistor circuit in the chip for flip-flop 4 is likely suspect. In your shoes I would still replace the chip.

Thank you very much. I will give it a try!

1 week later
#4 2 years ago

Quench - Just wanted to give a quick update. USPS and Marco let me down, so it took way too long to get the chip.

Replacing Z12 worked!

Thanks again!

IMG_7517.2021-08-17 09_16_50.gifIMG_7517.2021-08-17 09_16_50.gifIMG_7520 (resized).jpgIMG_7520 (resized).jpg

#5 2 years ago
Quoted from jsm174:

Replacing Z12 worked!

Great, and thanks for the update!

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