Corsair RM650 ATX, possibly struck by lightning

[Sam “Captain” W. C]

Just starting out in electronics repair and teaching myself as I go.
I have here a Corsair RM650 ATX PSU, which I'm treating as a learning project that if successful may be used in my PC.
Fuse was blown, probable power surge from lightning, followed the circuit and found, a dead relay and all the diodes and resistors around the bridge rectifier shorted. Rectifier and MOSFETs seem fine on the LCR.
Also found these tiny diodes on the other side, a few shorted, the rest seem fine. But they're not all marked as Zener on the pcb. So I'm unsure what these should be replaced with.
Any tips on how to proceed?
Fairly sure the surge didn't make past the transformers, but how could I make sure?
Just don't want to miss anything before I power it on.
Thanks

[Sam “Captain” W. C]

Also I'm having trouble identifying these resistors as I'm unsure which way to read the colour code.
The left one is either 28M or 16.8k.
fairly certain the right ones are 10k, but the black tolerance band is confusing me.
fairly sure there all 2W, they're 17mm long, 6mm diameter, 2mm wire, am I right?

[Sam “Captain” W. C]

OK so after some more work, the question I'm left with is how to determine the voltage rating of the smd diodes, as they have no markings, they are 5mm long by 3mm wide.
Ideally without probing it when connected to mains.

[harp]

am I right?

No.

Left - brown blue silver red, so 16x0.01ohm 2%
Right both - brown black silver gold, so 10x0.01ohm 5% --- 0.1 ohm

You literaly see resistive wire wrap arround package few times, there is no way that is 16k or 28M... nor 10k. Always be descriptive when asking for help, how you see that...


Do not rush... learn about basic component and measuring, practice desoldering soldering on some scrap board.

found, a dead relay and all the diodes and resistors around the bridge rectifier shorted.

What you mean dead relay, how you test it?
The resistors dont shorted, and around bridge rectifier, is there another diodes and resistor?

Rectifier and MOSFETs seem fine on the LCR.

What LCR and how you tested it?

I see, you are desoldering a bunch of components from pcb at the same time... must say that is not a way to troubleshoot psu. If you are just experiment and it is irrelevant to repair, it is fine, but if you ask to learn a procedure, or expect to some guide you and give you a tips, this is no-no category.

[Sam “Captain” W. C]

OK thank you, that's a huge help already, I was thrown off by the black ring at the end.
And don't worry, that's exactly what I'm doing.

And I just powered the relay and got a click on and off. So I was wrong there.
And I assure you the resistors are short, and they came from the negative DC pin of the bridge rectifier.

There are diodes on AC pins of the bridge rectifier both seem fine,
Plenty of resistors too, which I'll go round and check tomorrow. It's getting late.

I used a LCR-T7 to test the MOSFETs, out of circuit, and they showed up matching their data sheets.

Yeah its not essential that the PSU is fixed, I'm just using it to learn some stuff, be nice if I do manage to fix it though.

Thank you for your answer, really appreciate it.

[CapLeaker]

These resistors are so low in ohms they appear as short and belong that way. Different it would be if they have have resistance or open, because they would be out of spec. Your PSU would starve of power or have no power, the resistors would be baking hot and blow (open).

[harp]

Black ring on the end is probably thermal coeficient or so.
I assure you, that resistor on picture is not shorted, it is low ohm resistor, it can not have lower resistance that what have wrapped wire on him. And wrapped wire have 0.16 ohm.
Not all dmm are precise in low resistance reading. But, check on yours T7 transistor tester, what value measure for that resistor?


BTW, just now notice... your dmm leads are wrong connected. In attachment it is correct. Black leads always must be connected to COM port, it is refference point of all measurements.
When you do so, connect strongly together both leads (red and black) and write down measured resistance value of shorted leads, that might be like 0.3 ohm to 0.6 ohm... this is pure resistance of your leads, that do matter in low resistance measurements.
Now, test again your 0.16 ohm resistor, it should measure say about 0.8 ohm, and substract value of your shorted leads, and your measure will be close enough.


So, inspecting your board...
What is out:
- input wires
- input fuse
- graetz
- power resistors x6?
- TO220 x4
- heatsink
- standby transformer
- and few other unknown parts...

I hope that you write down from where to where is some component tooked, orientation, value...

About your questions for diodes: there is few common type of diodes:
the rectification diodes, for mains, voltage drop is like 0.6v
The switching diodes, have voltage drop about 0.3v
Small signal diodes
And zenner diodes

You are about a small signal diodes, it is for general purpose small glass signal diode like 1N4148 simmilar characteristic. They have rated for relatively high voltage but very small current. The marking ring is easy varnish by scratching, touching etc. due to slippy glass surface, they are marking on catode side.

Switching diodes work on high frequency and current, but lower voltage, to about 50V or so, called schottky diode, have smaller voltage drop

Do not mess arround with this small glass diode because they may be zenner which is crucial for some regulation circuit. If you spin it around you may burn something else or waste hours and houres to find fault.

[Sam “Captain” W. C]

Ok, I'm with you now, apologies for being dim.
tested the resistors with the T7 and they show up as you said they would.

So that just leaves the several shorted diodes, one 600V rectifier diode (1N5406), and the smd ones (LL34)

Thanks again for clearing things up for me.