Re: overvoltage to a circuit board lamp
The MOSFET gate drives are level shifted by the 4504 IC. I would hope the gate voltages be either 0 and 13V, at least before (and ideally after) the 100R resistors R2 and R5. If the voltage difference across R2/R5 are significant, likely the IRF540 that it's controlling has shorted out and failed.
A hack is to replace the 0R47 R3 that you've been messing with with a much higher value though it will dissipate more energy, though make it high enough and the lamp can't draw enough current to light full brightness and it starts pulling less... but based on the voltages you say you're seeing, this resistor is going to get even more toasty unless you get it to draw less through the lamp (or a low power LED...)
I still don't know exactly why they built it this way. The first guess was current regulation, which is ludicrous for an incandescent lamp. The second guess I have is burn out detection - if it has this feature and it pointed out that it needed a lamp repaired, then that would explain things.
The MOSFET gate drives are level shifted by the 4504 IC. I would hope the gate voltages be either 0 and 13V, at least before (and ideally after) the 100R resistors R2 and R5. If the voltage difference across R2/R5 are significant, likely the IRF540 that it's controlling has shorted out and failed.
A hack is to replace the 0R47 R3 that you've been messing with with a much higher value though it will dissipate more energy, though make it high enough and the lamp can't draw enough current to light full brightness and it starts pulling less... but based on the voltages you say you're seeing, this resistor is going to get even more toasty unless you get it to draw less through the lamp (or a low power LED...)
I still don't know exactly why they built it this way. The first guess was current regulation, which is ludicrous for an incandescent lamp. The second guess I have is burn out detection - if it has this feature and it pointed out that it needed a lamp repaired, then that would explain things.
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