Hello,
I currently fail modding a LiteOn SMPS from 12V to 24V, though having modified countless other SMPSs successfully before.
The relevant part of the circuit is attached to this post. (unpopulated parts removed)
My approach was to modify the resistor divider formed by R62 + R64 (R65 = 0 Ohm).
It's resulting voltage is compared with the internal 2.5V reference voltage.
As mere calculation of the divider did not result in a working PSU, I've replaced R64 with a pot...
Whenever the output voltage exceeds about 19V DC, the PSU shuts down – I fail to understand why.
Can anyone give a hint?
Note that I've also replaced R57 by double the value in order to not blow the LED in the OC, and C54 with a 25V type.
Thanks!