Re: APEX model LE 1910 (LED TV)
I think I may have misunderstood the reset pin. I've re-examined the Sanyo circuit and ISTM that the reset pin should be at 0V when the CPU is running and high when it is in the reset state. I'd welcome the opinions of others, though.
I've attached the relevant part of the Sanyo circuit. Unfortunately IC5900 doesn't appear in the parts list, so I can't refer to its datasheet. However, datasheets for suitable candidates suggest that Vout is low when the supplies are low, and high when the supplies are up. Also, if we eliminate all those optional (?) components that are marked with an "X", we are left with a reset circuit consisting of the transistor and an RC combination at its base. This would also suggest that the reset pin transitions from high to low at power-on.
https://cdn.badcaps-static.com/pdfs/...231e293dc5.pdf
https://cdn.badcaps-static.com/pdfs/...d7ffcb04ef.pdf
In short, I believe that your measured reset voltage is correct. As for the crystal, one would expect that the DC voltage should be biased somewhere in the middle of the supply, as it appears to be. You would need to measure its frequency with a scope before you could tell whether it was oscillating, though.
I think I may have misunderstood the reset pin. I've re-examined the Sanyo circuit and ISTM that the reset pin should be at 0V when the CPU is running and high when it is in the reset state. I'd welcome the opinions of others, though.
I've attached the relevant part of the Sanyo circuit. Unfortunately IC5900 doesn't appear in the parts list, so I can't refer to its datasheet. However, datasheets for suitable candidates suggest that Vout is low when the supplies are low, and high when the supplies are up. Also, if we eliminate all those optional (?) components that are marked with an "X", we are left with a reset circuit consisting of the transistor and an RC combination at its base. This would also suggest that the reset pin transitions from high to low at power-on.
https://cdn.badcaps-static.com/pdfs/...231e293dc5.pdf
https://cdn.badcaps-static.com/pdfs/...d7ffcb04ef.pdf
In short, I believe that your measured reset voltage is correct. As for the crystal, one would expect that the DC voltage should be biased somewhere in the middle of the supply, as it appears to be. You would need to measure its frequency with a scope before you could tell whether it was oscillating, though.
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