Reusing power supply from a printer - please help.

[mvoltin]

Hi, I am fairly new to electronics and need an advice on reusing PSU from a printer (please excuse my terribly non-technical language below). I already spent 2 days it it is much easier to buy one but this has become a challenge. I took apart two large printers and have the same issue: 3.3v, 5v and 12V work fine but 24v does not output any current. It requires some kind of feedback or input with a lower voltage (just like ATX power supply) but cannot figure out how. Tried just about any kind of loop-back with "flowing" or "static" current to no avail.

At this point I am not trying to "fool" the PSU to output the 24V but rather trying to figure out the PCB and modify it (with desoldering parts or adding a few) so that the output happens without any kind of feedback (is there a relay that is controlling the output?). This would also allow not to have a 5v supply running on a side all the time. The first picture is the entire set-up when trying to hack it. The rest of the pictures are the closeups of the PSU's PCB. thank you in advance.

P.S. Will be happy to provide chip numbers on the PSU board if this helps

 

[juni1122]

just tell me what you want to do with the power supply?

 

[mvoltin]

Hi Juni,
I am getting into electronics and making a CNC printer, router, some toys for my son, etc. As I mentioned, buying a PSU is much more cost-effective when you factor the time spent on it but it has become a challenge. Plus, if I can get it working, the quality of the PSU on this must be much better than stuff off the ebay. So, I wanted to possibly use it for small CNC set-ups or some other toys. thanks.

To repeat from my earlier post, I was hoping that someone familiar with the PSU design and using the initially enclosed pictures, could identify parts essential for the DC generation vs. parts that could be used for feedback so that I could modify the PCB to eliminate the feedback process altogether.

 

[chuckey]

If there are ANY voltage outputs from the PSU, try putting a load on them. PC PSUs need a load on the 5V to get all the voltages to work. If no output, check to see if there is any HV DC from the mains circuit. be careful.
Frank