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Discussion Starter · #1 · (Edited)
I have an A9L apart that needs new capacitors. While i'm here, i wanted to learn a bit more about the inner workings of the A9L. I've identified all of the transistors and what they control, but am looking to see if anyone knows what component on this board is responsible for the 5V reference voltage.

I do know that the top-most transistor in the bank on the right side of the above image seems to be a gate for VREF to pin 26 on the ECU. But my question is what generates the 5V Vref? If this was bad on an A9x, what component would be replaced?

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Discussion Starter · #2 · (Edited)
Oh BTW,

Fuel pump control, pin 22 is this transistor here circled in red. So if you have a constantly running fuel pump and replacing the capacitors doesn’t solve it, this is the one to investigate.

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5v reference is created out of the MCU. We are designing a drop in replacement A9L right now. We have a few test systems built and flashed the chips with the correct “firmware”. It will even work with a QuarterHorse as it won’t know the difference. Next step is to make a “high end” version with new MCU that is faster and more options.
 

· The Lurker
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5v reference is created out of the MCU. We are designing a drop in replacement A9L right now. We have a few test systems built and flashed the chips with the correct “firmware”. It will even work with a QuarterHorse as it won’t know the difference. Next step is to make a “high end” version with new MCU that is faster and more options.
Very interested in this as an option. While A9L are usually sought after for the Fox guys, I'm sure many improvements could be made over 80's tech. Keep us updated please!
 
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· Indo-Canuck-Yankee
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5v reference is created out of the MCU. We are designing a drop in replacement A9L right now. We have a few test systems built and flashed the chips with the correct “firmware”. It will even work with a QuarterHorse as it won’t know the difference. Next step is to make a “high end” version with new MCU that is faster and more options.
What microprocessor are you guys considering/using for the new design?
 
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