So the pop bumper is no longer locking on?
0 on the CPU board display and then going blank is normal.
What is the blanking signal doing when this happens? 5v or 0v?
Did you replace the bad PIA that you swapped earlier?
(Topic ID: 307365)
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Nope, the part you got from Marco is an exact replacement - assuming it works. How exactly did you measure the 1455 (555) timer chip with a meter to determine it was bad? They rarely go bad and I'm not aware of a way to test them outside a sample circuit.
Put your meter on Test Point 4 on the CPU board. 5V here is good. 0V here means the blanking circuit is blanking the machine to protect itself or due to a malfunction in the blanking circuit.
If could be you messed it up when replacing IC23.
Could be a bad PIA in IC18
Did you touch anything else in the blanking circuit? Caps, resistors, IC7, Q1?
Quoted from The_Great_Man:Plugged the game in this morning and turned it on with the coin door and backbox closed. The GI lights came on, nothing came on on the displays, the playfield lights did not go on. When I opened the backbox - the number 2 was on the Diagnostic display on the CPU. This means an error with the chip IC 16 Ram. I have read some things about this diagnostic that it should only be used with the backbox and/or coin door open. Is the reading I got with the coin door and backbox closed - 2 - a real diagnostic?
There is a Memory Protect error you will get if the coin door is closed when you press the diagnostic button. I don't think the coin door impacts the other boot up tests.
That being said, other failed chips can prevent the CPU from accessing the RAM and triggering an error. In other words, the error is real but the cause is not automatically the RAM itself. You could have bridged traces in the data or address bus. A failed chip on either of these busses could cause this error. Installing a PIA or other chip on the these busses backwards. 100s of potential causes.
No way it was 143 volts. The boards would be smoking if it was that high.
A 0 stuck on the board display means the cpu is not booting at all. Things are getting worse.
Quoted from The_Great_Man:Yeah I have read that so many times. Bottom line with that article…If your System 7 locks up - Go get a new CPU because it will be a miracle if you find the cause.
That is not true. Many of us have repaired boards in the same condition as yours. You need some diagnostic skills, some simple tools and some level of understanding of electronics.
The hardest part about your board is that it’s was mostly working and something you did to it when shotgun replacing parts has made it stop working. There is going to be a broken trace, bad solder joint, solder blob shorting traces or some other needle in the haystack that is now causing your board not to boot that is super hard for us to help you find without having the board in front of us.
That blob on that cap is not going to cause the problem.
Quoted from The_Great_Man:When I just checked that capacitor with my DMM - I did not get a reading. Any thoughts on that screw up/
[quoted image]
How exactly are you testing that cap with a DMM? What are you expecting to see to confirm it is good?
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