Need help using a power supply unit

[Smartie]

Need help using a power supply unit [Solved]

Hey everyone,

I've begun work on reverse engineering a Epson Stylus C63 printer for my 3D printer project I want to build this year. It's been going pretty well so far. However, I now need to figure out how to enable/disable the power supply unit so I can use it for myself.

The power takes in 240V AC, outputs 42V and 5V.
The connector for the PCB has four pins on it, 42V, 5V, GND and PSC.
I'm guessing that the PCS is used for turning the unit on and off, however I can't get it to work myself

I've connected a 10KOhm resistor in series with a LED to 42V, and and 390Ohm in series with a LED to the 5V. I plugged in the power and the 42V LED lights up bright, but the 5V wasn't going, so I unplugged the power and let the unit discharge (the 42V LED slowly faded out). I then tried again with PSC grounded, this time the 42V LED was dim, un-grounding the PSC pin made the 42V LED go bright again after the the power was already removed.

I measured the voltages of the pins, 42V and GND measured 42V, PCS and GND measured 37V, while 5V and GND measures -3V and quickly dropped to -0.2V (consistent when testing multiple times).

That's the best I can provide at the moment, Can you guys help me out in understanding this? I've posted the schematic for the power supply and the printer's main board below (the full schematic is on the last two pages of the service manual).

Cheers
Roman

 

[MikeMl]

The PSC terminal is an input to the Power supply that will turn it on when current flows to ground.

Connect a 1K resistor in series with a 10K pot wired as a rehostat (so the minimum resistance is 1K, and the maximum resistance is 11K. Connect one end to PSC, and the other end to the GND terminal at the power supply. Turn on the supply, and vary the pot downwards. At some point the supply should turn on the 5V. Note the resistance where this happens, and then try it with a fixed resistor ~one half of the measured resistance.

 

[Smartie]

The PSC terminal is an input to the Power supply that will turn it on when current flows to ground.

Connect a 1K resistor in series with a 10K pot wired as a rehostat (so the minimum resistance is 1K, and the maximum resistance is 11K. Connect one end to PSC, and the other end to the GND terminal at the power supply. Turn on the supply, and vary the pot downwards. At some point the supply should turn on the 5V. Note the resistance where this happens, and then try it with a fixed resistor ~one half of the measured resistance.

Hey Mike, I gave that a try but with a 50Kohm pot and I found that as the resistance is lowered, the 42V LED get dimmer as if a capacitor inside the PSU is discharging. when i increase the resistance, the LED takes longer to fade out. Nothing on the 5V LED though >.>

 

[Smartie]

A quick update, I plugged the power into the printer's board and measured the DC voltage on the pins. when the board is on, I measured 42V,4.3V 0, 37V (+42V,+5V,GND,PSC) when the board was off, i measured 2.1V, 0V,0, 0.6V.

but what I found interesting that when I measured a pad that was connected to the 5V rail, rather than the +5V from the power, i measured 4.9V. I'm guessing 5V being generated on the printers board and being supplied to the power PSU...

 

[Smartie]

Ah, after studying the schematic, I found that the 5V is generated on the board by the quad motor driver. this is a Custom part Epson designed with Allegro.
So what I can tell is that 5V is provided to the PSU for some reason and PSC is used to discharge the PSU when it's not in use.