350w SMPS troubleshooting.

[mb3]

I have a meanwell clone s-350-36, which has broken, IIRC due to crossed speaker cable. I would like to fix it both for use and to improve my understanding. I have tested the defective unit and mapped the voltages across the board

Areas without colour tested as 0 V.

I have tried to overlay this over the front face of the board too;


And here is the front with no overlay;


So to me it seems that the most likely broken component would be the small yellow/black part above the space between the two large capacitors, as this seems to have power one side but not the other. Which i believe is a transformer?.

Does this seem likely?
Is it something that would likely be damange by shorting speaker cable (or possibly one terminal hanging loose)?

Would you expect further damage to other components??
If so is there anything i can do to test that without risking breaking another transformer(?). ?

If it is a broken transformer, how do i go about replacing it (cheaply)? .. how do i know which type? the only thing i can see written on it is S 6.
Is this something that can be DIY'd?

Thanks in advance.

[zeus_threat]

Hi i've seen your post. Am not an SMPS expert but am struggling my way through. That black and yellow transformer is if am not mistaking a gate drive transformer. Its purpose is to provide the driving signal to your power transistor or power fet and to isolate the SMPS chip and driving circuitry. up to now i've blown fuses and power fets while building my SMPS but never that transformer. It cannot be replaced blindly as its custom made for your PSU frequency and tuned for your power switch driving signal

From your voltage mappings(RED shaded tracks) the input section might be OK your fuse does not seem to have blown.

Now normally there are protection circuits in SMPS (over current, over voltage, under voltage over temperature, e.t.c) which trigger in case there could be a fault in the SMPS. They will to keep it simple prevent the psu from turning on. if you are getting voltage on part of the drive transformer it could be one of your power switch or both has failed. POwer off the circuit, let the mains cap discharge and check these switch.

For your info two very important points, that PSU you have here seems to me like a half bridge. You can search on this on the net and get tons of info on how it works.

Last but not least to built or repair a psu an oscilloscope is needed, its really hard to deal with SMPS without one handy as all the problems in an SMPS can only be diagnosed through the waveforms its producing

I have labelled some of the sections from what i could recognise visually in the attached file

[mb3]

Thanks for your reply and image!.. sorry for my delay.

Is an H-bridge the same as a half bridge?? Can anyone point me to a good learning resource on this?

How do i check the power switches aren't broken exactly??

[mb3]

Originally Posted by mb3

How do i check the power switches aren't broken exactly??

Anyone?

Would one of these; ebay: 2 Channel PC Computer USB Digital Storage Oscilloscope be suitable?

And what would i be doing with a 'scope in this scenario and how would that bring me closer to a solution?

[zeus_threat]

You seem not to be well used with those things it can be dangerous for you. I would advise to get it repaired at a electronics service workshop it will be easier. That scope is not good for the job anyway

[!]

I really hate trying to trace faults from pictures but... it looks a bit like you've measured voltage on one side of the main (larger) transformer, did you not continue trying to measure voltage on the other side, or was there no voltage present? See if any voltage is present on the output rectifier's pins.

[aymantn]

power supply troubleshooting and repair guide
SMPS Troubleshooting Techniques