Quick Questions: Easy EDA and a couple simple couple circuit Q's

[cdnmatt]

Hello new guy here from Canada, I keep running into this forum the last few days and I am now on the hunt on how to expand the pcb area of EasyEDA as I am now running up towards the border. I tried to use EasyEDA last week, but I couldnt figure out how to get new symbols, which I now know how to do.

What I am doing is mapping out a pcb board for a Meanwell PSU (HRP-300-24) as I have several that are not working. The fuse keeps blowing because something "downstream" is damaged and I believe it is the Diode Rectifier. I have ordered an ESR in order to test Capacitors in circuit, like the Mylar input caps next to the transformer that boosts voltage, its basically two coils on one magnet ring, split in half.

A quick question on the Neutral line, there is a small wire right at the AC input: N connection, what is that?
It's obviously not a shunt, so I am guessing it must be a wire fuse. Also there is a Thermistor, a green disc labelled RTH1 so I hope the ESR can measure that.

Not much else to check, there is a big relay that has 4 pins, big diode. I will attach a screenshot if I can as to where I am at now.

I am sure I have some more basic questions for you guys, but I try my best to search out the answers. I haven't yet mastered the skill of how to narrow search results so I stumble along the best I can.

[mvs]

The fuse keeps blowing because something "downstream" is damaged and I believe it is the Diode Rectifier.

Diod bridge can withstand a lot of abuse. But to be shure, you can test each diod with DMM.

I have ordered an ESR in order to test Capacitors in circuit, like the Mylar input caps next to the transformer that boosts voltage, its basically two coils on one magnet ring, split in half.

X2 rated film caps are overdesigned for safety and should be ok, do not waste your time on them. The "transformer" is actually a common mode choke.

A quick question on the Neutral line, there is a small wire right at the AC input: N connection, what is that?
It's obviously not a shunt, so I am guessing it must be a wire fuse.

I would say just a jumper wire...

Also there is a Thermistor, a green disc labelled RTH1 so I hope the ESR can measure that.

It is probably NTC for inrush current limiting. You can measure it with DMM. In cold state it should have resistance of few Ohms.

Not much else to check, there is a big relay that has 4 pins, big diode.

A relay can be used to limit inrush current, but it is a bit unusual solution for just 300W power supply. The diod can be a part of PFC boost stage.

I will attach a screenshot if I can as to where I am at now.

Its a good idea.

[cdnmatt]

Thank you mvs!

The EasyEDA border issue, I just copy the entire circuit and open a new document. I did figure out how to initially set the working area, but not how to set it when circuit is already placed.

That "jumper wire" on the Neutral line is soldered in, and it is labelled as FS2, obviously a fuse. Surfing Youtube last night, I found out that some companies put a fuse on the metal tabs where the tab gets really narrow, then back to full width. The COnquer CQ MSF Radial fuse is also soldered in, easy to replace.

The rectifier is confirmed bad because the diode check does not work, both ways in all positions. Since it can take a lot of abuse, I can only hope that the rectifier saved the psu from further damage, but I will continue t/s down from that.

You did nail it mvs, I spent an hour scraping away the goo to find the info on that EMI Supression, metallized polypropylene cap. AVX Kemet R.46, X2, SH (Self
Healing)m 0.68uF. Big dark components next to the choke.


I sized the pictures right, also I need to correct a few things on the schematic, like the choke notes and the component labels (C#, R#)


Thanks