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Weird System 11 fault (Dr Dude).

Pick Holder

Pick Holder

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5Years
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Jul 18, 2016
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Bournville, Birmingham.
Okay - weird fault.
Using the door switches it seems the UP/DOWN button is 'stuck' in one place according to the CPU board - so I can only get into music test (pressing start decreases the numbers - and I can not get past this).
The game has a couple of other faults (it is a Dr Dude).
Before anyone pipes in with 'its the door switches' it is not. Been doing this for over 20 years and I have a made up test button set up that plugs straight onto the CPU board.
Have changed U14 so far and then U36. I would change U35 but do not have one. Checked resistors and capacitors on the input for any open/shorts and nothing strange - I changed the caps anyway.
The only strange this is the resistor array between U14 and U15 has a different reading on two of the pins (it goes down to about 24 ohm) - and when the EF6802P is removed this fault retifies.

I need to get into the test menu as even when the game is booting - two lights on the playfield are flashing. They continue to flash when game is booted up.

Any suggestions.
 
Pick Holder said:
Okay - weird fault.
Using the door switches it seems the UP/DOWN button is 'stuck' in one place according to the CPU board - so I can only get into music test (pressing start decreases the numbers - and I can not get past this).
The game has a couple of other faults (it is a Dr Dude).
Before anyone pipes in with 'its the door switches' it is not. Been doing this for over 20 years and I have a made up test button set up that plugs straight onto the CPU board.
Have changed U14 so far and then U36. I would change U35 but do not have one. Checked resistors and capacitors on the input for any open/shorts and nothing strange - I changed the caps anyway.
The only strange this is the resistor array between U14 and U15 has a different reading on two of the pins (it goes down to about 24 ohm) - and when the EF6802P is removed this fault retifies.

I need to get into the test menu as even when the game is booting - two lights on the playfield are flashing. They continue to flash when game is booted up.

Any suggestions.
Click to expand...
Check the resistor network. I have seen them look perfect but are cracked and lead to weird faults.

David
 
Sounds like you answered your own question. Resistor bank is pulled low by 6802.

Have you another 6802 to try and does it have the same effect on the Resistor bank?
 
Is the resistor bank still being pulled low with the new 6802?

Try checking what the other end of the resistor bank feeds.
 
What are the signal levels at U14 pin 8 and 10? Edit: when button pressed and released.

David
1724686174814.webp
 
Last edited:
Okay all -

Just an update on this if anyone is interested in the future.

I found a via gone on the main board. Nowhere near the batteries.

The low resistor network was a red herring - as it was fine without the CPU in. I tested other cpu's and they all dropped the resistance down on one network resistor.

After I found that issue I sorted out the rest of the repairs and re-capped all the boards to (attempt) to make it future proof.

Tomorrow is rebuild flipper day and re-rubber etc......
 
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