After checking the power MOSFETs, voltage references for feedback, and the PWM & power factor correction controllers they all checked out, and gave signals that I was expecting/calculated. I also successfully loaded it to 1.5A (PSU cable of 3A) without a glitch. When I manually pulled the optocoupler high the PSU went into full swing and output the 17 VDC correctly. This meant the PSU sat at 10 VDC as in dot point 5. I also worked out that because of the short, the optocoupler responsible for enabling the power supply output wasn’t being turned on. This was causing the short circuit protection of the PSU to activate and disable its output (ie setting its output to 0 VDC). The projector is diagnosed and fixed!! Turns out there was a short circuit on the processor board. My thought is - if it powers up from the bench supply and provides some activity on the status LED’s then that’ll add evidence to the problem existing at the main PSU.įinally managed to spend some time on this project this past weekend. I see switching regulators, so perhaps it has some tolerance to input voltage. I have thought of powering the processor board using my bench PSU - I just don’t want to risk damaging the processor board until I’ve investigated the input range it can handle. Nonetheless I will continue investigating.Īt this stage I’m not sure if I can trust the 17V DC marked on the main PSU’s silkscreen. (This is where I was hoping for a service manual to help me along). I’ve started reverse engineering the power supply a little to double check that the PSU IC, transistors and other components are working/biased correctly. It could therefore be struggling to source enough power for the processor board to boot up? Perhaps the main PSU is not working properly (indicated by 10VDC being measured instead of 17VDC). Power on, and the supply’s output measures in at 0 VDC again.
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