I have spent the last week trying to fix something that wasn't broken in the first place.
This is why I don't trust electricity; if you have a non-functioning pop bumper, you can usually figure out the problem just by looking at it, or by using some really simple testing equipment. Not so with circuit boards, at least not the variety used to build Flash.
I have a System 4 Flash, although Williams later built Flash using a System 6 hardware set of circuit boards. I only had access to the board diagrams for System 6, which are pretty similar to System 4.
Unfortunately, one of the changes made from System 4 to System 6 (which I was unaware of), was the movement of the CPU chip and the Peripheral Interface Adaptor (PIA) chip, to roughly opposite positions on the MPU board. The are both 40-pin chips, and are not labelled in any clear way to identify their function.
I dutifully followed the detailed instructions for diagnosing problems with the MPU board, using the proper testing chip, etc., for the past week. I diagnosed a problem with the PIA, and therefore tried replacing it.
But when I did, things got worse, not better, and the diagnostic program stopped working altogether. Thinking I had a bad new PIA chip, I bought another and replaced it again, but with the same result.
Of course, the entire time, I was actually trying to put a new PIA chip into the old CPU socket, with less than ideal results, as you might expect. As it turned out, both my CPU and PIA were working fine, I just couldn't tell because I was testing them for the wrong set of signals. I finally figured this out on my own, after a week's time, much consultation with the pinball repair experts on the internet, and countless trips back and forth to my local electronics store. A dumb thing to get caught up on, but I guess to be expected for someone who didn't know a thing about pinball circuitry only four months ago.
Time for a week-long vacation now, so Flash will just have to be patient.
This is why I don't trust electricity; if you have a non-functioning pop bumper, you can usually figure out the problem just by looking at it, or by using some really simple testing equipment. Not so with circuit boards, at least not the variety used to build Flash.
I have a System 4 Flash, although Williams later built Flash using a System 6 hardware set of circuit boards. I only had access to the board diagrams for System 6, which are pretty similar to System 4.
Unfortunately, one of the changes made from System 4 to System 6 (which I was unaware of), was the movement of the CPU chip and the Peripheral Interface Adaptor (PIA) chip, to roughly opposite positions on the MPU board. The are both 40-pin chips, and are not labelled in any clear way to identify their function.
I dutifully followed the detailed instructions for diagnosing problems with the MPU board, using the proper testing chip, etc., for the past week. I diagnosed a problem with the PIA, and therefore tried replacing it.
But when I did, things got worse, not better, and the diagnostic program stopped working altogether. Thinking I had a bad new PIA chip, I bought another and replaced it again, but with the same result.
Of course, the entire time, I was actually trying to put a new PIA chip into the old CPU socket, with less than ideal results, as you might expect. As it turned out, both my CPU and PIA were working fine, I just couldn't tell because I was testing them for the wrong set of signals. I finally figured this out on my own, after a week's time, much consultation with the pinball repair experts on the internet, and countless trips back and forth to my local electronics store. A dumb thing to get caught up on, but I guess to be expected for someone who didn't know a thing about pinball circuitry only four months ago.
Time for a week-long vacation now, so Flash will just have to be patient.
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