This is Tutorial is from obdexpress.co.uk office blog how to raise voltage from 3.3v to around 3.7v for a UPA-USB device programmer as 3.3 don’t read some chips and 4.8 is too high for some.
Raise voltage via UPA USB V1.3
UPA USB V1.3 hardware test pass 100%
Reason for voltage change:
reading s93a66…. fine but wanted to transfer data to 93c66 and wouldn’t read or write on 93c66 until I set jumper to 4.8v
UPA programmer voltage:
Options in program are only 3.3v or 4.8v controlled by jumpers
Check jumper 3.3V/ 5V
There are two series diode to drop 5v to 3.3v around 5/3.3v jumper. Try to make short to one of them now the 3.3v setting will raise about 0.6v but don’t know if the voltage monitoring circuit will report a problem!
or check the variable resistor in the UPA USB programmer
I read that ‘that’ was a fuseable link
It used to have a component marked N1 which was a fuse
It protect 5V power from top board to bottom board
when have the short circuit, it ‘ll change resistor first to protect other item.
After that, we need change it. can use fuse instead it
Disclaimer: You will try on your own risk!!