If attitude could fix it, you'd have it working for sure!

 

OK, I tried what you suggest, and indeed there is 300 VDC at points 1 and 2, however points 2-3 and 1-3 give no voltage at all no AC no DC

what about 4 and 5?

 

If attitude could fix it, you'd have it working for sure!

Sorry, I'm not following, can you explain?

I am sorry if any comment was offensive, that wasn't my intention, I am simply trying to fix that thing, and I might sound a bit upset in regards of how weird and complicated it is, but I don't mean anything bad by it.

 

OK, I tried what you suggest, and indeed there is 300 VDC at points 1 and 2, however points 2-3 and 1-3 give no voltage at all no AC no DC

what about 4 and 5?

You need to measure between (3 and 4) , and (3 and 5) to see if there is any output.

 

You need to measure between (3 and 4) , and (3 and 5) to see if there is any output.

I did, black lead on 3 and red on 4/5, there is 0 VDC on either.

 

I did, black lead on 3 and red on 4/5, there is 0 VDC on either.

Okay so the power supply isn't working so what is the number of the chip on the heatsink ( photo).

What is the slotted photo diode for ? ( photo)

 

i will check the chip number in a couple of hours (I am no longer in my workshop), the photo diode (if you are refering to this black U shaped thing) is techically a sensor, it signals the printer whether or not there is paper in the tray, there is a plastic lever thing that goes inside the tray, and the other end slots in the middle gap, so I guess it has nothing to do with the actuall power delivery , in one on the images it says "Feed sensor" next to it, but it's not completelly clear an the image, it's blury, but that's what is written.

 

the chip number is:
DK49
DM0565R

 

This is the nearest circuit i can find to your pcb, ( it won't be exactly the same) see if there is a 300V DC on pin 6, it comes from the capacitor via the 3 resistors R5/6/7 , these are in series, one might be blown.

If you're not familiar with switch-mode PSUs then i strongly recommend that you proceed with caution, or get someone to help you.

 

This is the nearest circuit i can find to your pcb, ( it won't be exactly the same) see if there is a 300V DC on pin 6, it comes from the capacitor via the 3 resistors R5/6/7 , these are in series, one might be blown.

If you're not familiar with switch-mode PSUs then i strongly recommend that you proceed with caution, or get someone to help you.

View attachment 304533

thanks, there are some differences on my PCB, but I understand it a little better now.

there is 290 VDC at pin6 at the DM0565R VRM, all three resistors are good, the voltage starts at big capacitor (300 VDC) and it goes through 3 resistors, loosing about 3 VDC per resistor.

 

It's worth checking any diodes and capacitors around the chip, for shorts , if it's working there should be around 20 V on pin 3, pin 4 is the voltage regulation control, (this will be controlled by an optocoupler probably by the side of the transformer,) this should be around 10 to 15V if it's running and zero if it's not. The optocoupler is switched on by a TL431 Zener diode ( U101 on your pcb) , the Zener fires and turns on the optocoupler which stops the chip, .
Hopefully you can solve it, otherwise chuck it in the bin..

 

It's worth checking any diodes and capacitors around the chip, for shorts , if it's working there should be around 20 V on pin 3, pin 4 is the voltage regulation control, (this will be controlled by an optocoupler probably by the side of the transformer,) this should be around 10 to 15V if it's running and zero if it's not. The optocoupler is switched on by a TL431 Zener diode ( U101 on your pcb) , the Zener fires and turns on the optocoupler which stops the chip, .
Hopefully you can solve it, otherwise chuck it in the bin..

Ok bellow I send an image with descriptions.

There is DC voltage at 2 pins on VRM, both 290-300 the rest of the pins are 0.

The optocoupler has 0 voltage on any pin, the same is true for U101 zener.
There is also no continuity between any pins on zener ( but I don't know whether or not there should be continuity, zener seems to be different from other diodes).

Other diodes and capacitors near the VRM seems to be fine, no shorts as far as I can tell.

I am not going to surrender that easily though, the more I dig arround this, the more I want to solve it.
I gave the PCB to a friend, his brother is a electrical engineer or something similar, anyway he is definitely more knowledge on circuits than me, and I belive it would be easier for him since he has the board and can test it live.

Thank you for your help, dodgydave, I appreciate it.

 

Ok bellow I send an image with descriptions.

There is DC voltage at 2 pins on VRM, both 290-300 the rest of the pins are 0.

The optocoupler has 0 voltage on any pin, the same is true for U101 zener.
There is also no continuity between any pins on zener ( but I don't know whether or not there should be continuity, zener seems to be different from other diodes).

Other diodes and capacitors near the VRM seems to be fine, no shorts as far as I can tell.

I am not going to surrender that easily though, the more I dig arround this, the more I want to solve it.
I gave the PCB to a friend, his brother is a electrical engineer or something similar, anyway he is definitely more knowledge on circuits than me, and I belive it would be easier for him since he has the board and can test it live.

Thank you for your help, dodgydave, I appreciate it.View attachment 304605

Okay then your next step is to replace the DM0565 chip, and take it from there, good luck.

 

Okay then your next step is to replace the DM0565 chip, and take it from there, good luck.

Very well, I will do that, it's like 1-2€, however, I don't know what kind of TIM sits between the VRM and it's heatsink, I have a regular CPU thermal paste, will that be enough? Or do I need something special for it?

 

Ordinary paste will do , it's on it's own heatsink.

There's a datasheet for this chip , it will tell you how it works.
https://datasheetspdf.com/datasheet/DM0565R.html

 

Ordinary paste will do , it's on it's own heatsink.

There's a datasheet for this chip , it will tell you how it works.
https://datasheetspdf.com/datasheet/DM0565R.html

I have been searching for this one now, but can't seem to find the 100% identical one there are all DM0565R but the other number is different, I have DK49, and All I find is DB49/DG49/DH49/DJ49, but no "DK" variant, is this number important?

Also it's just the module itself, no heatsink, at least not on the image.

 

These must be the manufacturer date codes, there's only two types 56 and 76, the 76 is a higher wattage.

 

These must be the manufacturer date codes, there's only two types 56 and 76, the 76 is a higher wattage.

Ok

 

These must be the manufacturer date codes, there's only two types 56 and 76, the 76 is a higher wattage.

Hi, replacing the VRM did it, the power supply now works flawlessly, and so does the printer.

Thank you all for your help, I appreciate it greatlly.

Best Regards