everything up to the hvdc works fine; it has ~160VDC on the caps. i haven't gotten back to it yet to know about the next step.cor wrote:Cool that it is a PFC supply. It should have 3 functional blocks: first the AC input with rectifier and PFC switcher, ending in the big caps that store the upconverted DC (usually 200 or 400V). Then comes the PWM controller and switching FET(s) to turn the HV DC into a square wave that drives the transformer.
yes, there are two. in this picThird, at the output of the transformer a rectifying diode, filter and shunt with current measurement, feeding back to the PWM controller, together with the voltage feedback. I did not see opto couplers on the pictures. Are they hidden next to the transformer? On the NES they are right next to the transformer.
i've been following your reverse engineering of the other mw with great interest. i've had to do that kind of thing before, but don't like it much. if i have time i will compare your existing schematic as drawn into program by neil, and update it for this version where i find differences. i definitely appreciate you dropping into this thread to help out.For fixing, you can check if the PFC stage is still making high voltage DC and then check the final stage for voltage (and current) control and other feedback (on the NES there is also overvoltage and overtemp protection feedback) before you try to attack bringing the PWM stage back to life, since the other parts affect the operation of the PWM controller.
amberwolf wrote:regarding the model designations, i found:
http://www.meanwell.com/webnet/search/s ... .html#open
seems to show that sp series has pfc while s series is not listed, but probably is same without it. i found a spec sheet for the s-340 series that doesn't mention pfc
http://www.soaring-cn.com/UploadImages/ ... Series.pdf
sp series doesn't show a 350, though, just a 320 then a 480, so i dunno.
well, mine says it's from 2008 on the pcb, so they might not make that line anymore. assuming it's not a clone from somewhere else.
amberwolf wrote:oops. my meanwell is an sp-320-48, not 350. i cant' read. so it is the pfc-type series i linked above. (note: fixed thread title)
mine has no shunt at all, at least, not as a wire-jumper type, unless i am just blind, as well as illiterate.
amberwolf wrote:now that i'm seraching for the right model number, i've found info on this one going back to at least two years ago jan 2010:
https://endless-sphere.com/forums/vi ... 38#p228838
as one example.
so they're not new and untried, but i havent yet found enough info to tell me what i need to know to fix it and use it.
unfrotunaely most of the pics i would like to have for reference are missing or trashed. edit: but aussiejester's site still has the hires ones he took:
http://members.ii.net/~aussiejester/ind ... 48v%20PSU/
even some partial schematis
amberwolf wrote:i found earlier and posted in the repair thread that the the pfc and pwm chip is not working--it appears to be internally shorted:cor wrote:If you get only 160V on the caps then that tells me that the PFC is not working, as that is the normal voltage of rectified 110V AC, not the boosted voltage of a PFC stage, so I would certainly recommend to test if the PFC switching FET is actually working and whether the ML4800 PFC and PWM controller is working.
just posted a minute ago in there that it's definitely shorted, and links to where i might be able to buy a new one.
ah, ok. i have a lot to learn about pfc, having rarely fixed any psus with it, and so far only having to replace bad caps that boiled from high temps in sealed units, or blown fets or output diodes from the caps having died.cor wrote:I noticed that you already found the datasheet with a reference schematic here: http://www.fairchildsemi.com/ds/ML%252FML4800.pdf
The 900V 9A PWM MOSFET 2SK2082 from Fuji Electric can be found in many places, for example: http://pdf1.alldatasheet.com/datasheet- ... 82-01.html and the PFC FET IRFP460A from IR can be found here: http://www.irf.com/product-info/datashe ... fp460a.pdf it is a 500V 20A N-channel MOSFET.
Please note that the voltage of the caps C5 and C?? is 400V, which is a typical PFC boost voltage from anything between 90-260V AC.
regarding the mosfets i actually have some spares of these out of other dead psus that had leaky caps and such, or were simply scrapped by someone else due to age, or not being needed, so i harvested all the parts i could.
i was following your schematic on the nes version, and this one is definitely a lot different, presumably because of pfc stuff and using the combo chip rather than just the simpler nes method. still, i will probably be able to take your schematic and modify it to match this one, with the output section being mostly the same, i think. i havent' tested or measured or traced anything on the output area yet.The location of the optos and the array of diodes under the transformer looks like the NES setup, but due to the extra complexity of PFC, the controller section is about twice as busy and you have an additional switching FET and rectifying diode.
i'd guess willis lu was the layout designer, so he or she "signed" the work. might be the actual engineer designing the whole psu, too.BTW, I wonder who Willis Lu is, who put his name on the PCB.
Just make sure that you don't test it while the MW is powered or you will blow the PWM FET.amberwolf wrote:all i can think of at the moment to compare is the resistance of pin 13 of that chip to ground (pin 10, I think), after you've unplugged teh mw from ac power and any load on it's dc out, and all voltage is drained from caps and such. i'm pretty sure it can't be a super-low resistance.
i can easily add a grounding resistor on the fet gates so they don't switch on. didn't think of them going linear but that's a good point.
the fets are not shorted because they don't have any voltage on their gate or output, only on their input pin. i haven't tested to see if they switch or not, but can easily do so. my fluke meter has enough voltage on it's ohm test to switch most fets