Hello everyone!
I need a power supply that can deliver 13.8Vdc (15% tolerance) at 3A for my radio.
I have an old (but working) HP laptop power brick, that supplies 18.5Vdc at 6.5A. The PSU is heavily shielded against rf emissions, so I think it might serve ok in it's future role.
The idea is to change the power supply to deliver 13.8Vdc by manipulating the feedback circuitry as described in
https://hackaday.io/project/3469-modifying-a-notebook-power-supply. The process involves feeding the secondary side with lab power supply.
My PSU uses TSM103/A comparator. I think I've managed to find the resistors that make up the voltage divider, but would like your opinion if I have the right ones. I'm trying to avoid unnecessary desoldering of super tiny smd components
If I understood correctly, TSM103/A pin 2 is the pin which I have to follow to find the desired voltage divider.
The divider I found consists of 49C (31,6kOhm) and two resistors 51D (332kOhm) and 556 (55MOhm) in parallel. Do these values sound reasonable? To me they seem very high, but that is how I interpreted the markings.
If the values are correct, that would make resistors 51D and 556 be seen as one 313.1kOhm.
What might be the idea behind using that 55MOhm resistor?
I gather it does not matter which part of the voltage divider I change?
The PSU output has three leads. V+, GND and ID. V+ and ID are connected together through 1,5kOhm resistor. What purpose might that ID lead have? Can I just ignore it, or does it have a vital role in the operation of the PSU?
Thanks for your time