- Faulty SMPSU. - 2 Updates
- cheap solder smoke filter or overkill? - 1 Update
- usb Parallel converter - 1 Update
| T i m <news@spaced.me.uk>: May 17 01:38AM +0100 Hi all, I know there are some very experienced / SMPSU folk on here so I'll run this by you if I may. The PSU on the MendelMax 3D printer I built with / for a friend over 5 years ago (then bought off him) died the other day. ;-( I noticed it had stopped towards the end of a 90 minute print and the printer was off (very unusual). I power cycled it and it appeared to come up again, but when I told it to preheat (extruder and bed) it nearly immediately powered down. Disconnecting the heated bed, the printer would both power up and pre heat the extruder but the software then halted the printer because it noticed the bed wasn't heating. ;-) So I dug out an old linear 13.5 x 12A PSU I had from my Packet radio station and used that to power the heated bed and the printer then ran ok and I was able to re-print the job. When I powered it down it didn't seem to go off as normal and after taking it out and removing the top, I noticed one bulging cap (one of 4 x 1000uF, 16V) on the output / smoothing stage, so replaced all 4. Alas (and sorta as expected), it didn't really help so I'm not sure what to do (and if it's worth doing) now (knowing how little I know about SMPSUs). However, I am fairly familiar with working on stuff that has mains and have been a component level field support tech for some of my career (Tele/datacomms/Microfilm and built all my own disco lighting) so don't mind giving stuff a go, if anyone is willing to point me in the right direction and thinks it would be worthwhile. This is the unit out of it's frame. Front https://ibb.co/5McshGF Rear https://ibb.co/w6Wq6hj I think it had a small fan, stuck to the side of the big transformer but it got noisy so we took it out and the PSU only used to run warm. That said, with everything on I think it was pulling current close to it's max rating so we can't complain that it's lasted that this long (heated bed ~10A (measured 11.5 on 13.5V)), extruder 3.5A, 5 x stepper motors at 1A each and a few fans and the Arduino Mega and LCD display etc). After changing the caps, I ran it up without a load and it was a 'flaky' 12V (onboard LED on but the voltage was waving about a bit) and when I fitted a 5A load, it wouldn't start up at all. (crowbarred?). I've measured the bridge (diode check on my DMM) and that seems ok. No strange noises, I did sense that 'hot electronics' smell when going back to the printer and it looks like the windings of the output choke thing are darkened but nothing obviously burned or blown. I assume the 3 legged device on the LV side is a switching transistor / FET of some sort and the 5 legged thing on the HV side, some sort of SMPSU controller device / IC? I can't tell what they are without desoldering them (but can do so etc). R7 looks like it's been warm but measured at around 4K7 I think. As an aside, a quick Google for LJYD-0540 suggests (and it's name <g>) it, or the PCB was designed to be a 5V 40A PSU and so has been built into a 12V 20A model somewhere along the line? Cheers, T i m |
| legg <legg@nospam.magma.ca>: May 17 11:00AM -0400 >it, or the PCB was designed to be a 5V 40A PSU and so has been built >into a 12V 20A model somewhere along the line? >Cheers, T i m You're running at 220V? OK Make sure the choke ends aren't touching as they leave the toroid center. Wires not shorting to core. No sign of cracked cores. Check big primary bulk electros - voltages should be roughly equal with small low-frequency ripple. Replace small electros on primary side, then optocoupler. A basic forward converter. Integrated primary switch should be replaceable, but check transformer Lp first. RL |
| "Peter W." <peterwieck33@gmail.com>: May 17 04:46AM -0700 > Never had a problem with kester #44 60/40. Works great, every time. How > life changing can this this 63/37 stuff be? I do not trust in pure blind luck being 100% effective 100% of the time. 63/37 solder removes some of that need. Peter Wieck Melrose Park, PA |
| Rob <nomail@example.com>: May 16 05:44PM > Basically my question is if the usb-prl converter works both ways. > Or how do I know if it does. Ok so that has been answered: It doesn't. |
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