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**senz_90** · 01-30-2014, 07:01 AM

Re: repair seasonic p860 with burnt/crack mosfet

changes the mosfet and test the power supply with light bulb to prevent your new mosfet burned again if there is still something wrong. i think it would better if you try to check surrounding components with mosfet.

**holmes222** · 01-31-2014, 12:02 AM

Re: repair seasonic p860 with burnt/crack mosfet

still finding the mosfet replacement here
curious ...how many wattage bulb to do the bulb test ?
100w or more ?

**senz_90** · 01-31-2014, 04:58 AM

Re: repair seasonic p860 with burnt/crack mosfet

yes. i think 100w is good enough. search light bulb trick threads from momaka post to see how to connects the bulbs. lower rds is better for mosfet replacement, the other specs need higher.
btw where is town that you live on?

gosh. original mosfet is 0.19 rds. that would hard to find the replacement. lol

**holmes222** · 01-31-2014, 02:25 PM

Re: repair seasonic p860 with burnt/crack mosfet

Originally posted by senz_90 View Post

yes. i think 100w is good enough. search light bulb trick threads from momaka post to see how to connects the bulbs. lower rds is better for mosfet replacement, the other specs need higher.
btw where is town that you live on?

gosh. original mosfet is 0.19 rds. that would hard to find the replacement. lol

lol .. find the replacement 6R190C6 mosfet from working seasonic x series

already had, actualy not to replace, just for testing purpose

if it pass the test .. i will order the original replacement

i wonder what make this mosfet burn out ??

here the result of hard work overnight till 3 AM ..

next day project = build light bulb tester and then test the unit ..thanx senz_90

@senz_90 .. i live in small town in central java (around slamet mountain)

Attached Files

**senz_90** · 02-01-2014, 01:43 AM

Re: repair seasonic p860 with burnt/crack mosfet

i am not engineer nor student, so i couldn't give a logical answer. maybe it was catastrophic failure, or badcaps those makes frequency didn't run precisely and due of wrong frequency mosfet has to run harder and hotter than usual, or maybe the others part failed and affect this mosfet.

it runs very hot and crack the mosfet into 2 pieces. don't forget to attach thermal paste between the mica insulator to mosfet and to heatsink.

central java is more better than me here. you couldn't get a good parts here especially good japan caps. hahaha. maybe you could help me to find someone those sell a good caps or smd components? i have think to digging into lcd/led tv repair so it would helps much.

**PeteS in CA** · 02-01-2014, 02:45 PM

Re: repair seasonic p860 with burnt/crack mosfet

Based on the blasted appearance of the die and the pit in the broken off molded-over plastic, my guess is that it was some kind of event that exceeded the rated voltage of the device. BTW, that little ferrite bead on the gate lead may be important both to control EMI and for good turn-on and turn-off (e.g., during turn-off the voltage change on the Drain and the Drain-Gate capacitance can actually turn the device back on, which can be quite destructive). So be sure to install that ferrite bead on the new MOSFET Gate lead.

**holmes222** · 02-02-2014, 04:03 AM

Re: repair seasonic p860 with burnt/crack mosfet

Originally posted by PeteS in CA View Post

Based on the blasted appearance of the die and the pit in the broken off molded-over plastic, my guess is that it was some kind of event that exceeded the rated voltage of the device. BTW, that little ferrite bead on the gate lead may be important both to control EMI and for good turn-on and turn-off (e.g., during turn-off the voltage change on the Drain and the Drain-Gate capacitance can actually turn the device back on, which can be quite destructive). So be sure to install that ferrite bead on the new MOSFET Gate lead.

thank for the information and explanation PeteS
yah i forgot to install the ferrite bead again on new mosfet ..will do that later

finished build dim build tester .. 100w bulb
test the unit and bulb just dim glow and off ..is this an indication that the unit is normal again ?
i test without shorting black and green wire , just turn on the psu switch
any suggestion ?

if i test with shorting green and black wire, should i give a load to the rail ? a fan or old cd/dvdrom maybe?

Attached Files

**senz_90** · 02-02-2014, 04:31 AM

Re: repair seasonic p860 with burnt/crack mosfet

Originally posted by holmes222 View Post

thank for the information and explanation PeteS
yah i forgot to install the ferrite bead again on new mosfet ..will do that later

finished build dim build tester .. 100w bulb
test the unit and bulb just dim glow and off ..is this an indication that the unit is normal again ?
i test without shorting black and green wire , just turn on the psu switch
any suggestion ?

if i test with shorting green and black wire, should i give a load to the rail ? a fan or old cd/dvdrom maybe?

From your word dim glow and off, it seems that ok. try measure the rails voltage and sure with jumpered and a load likes a big watt resistor or fan or harddisk. if you got voltage on every rails (especially on it's rating), that's mean your psu is more likely could be fixed or no problem anymore (already fixed).

**holmes222** · 02-02-2014, 06:44 AM

Re: repair seasonic p860 with burnt/crack mosfet

update ..
measure test, still without shorting ground to ps-on wire
check the voltage via 24pin connector
- ps-on (green wire) showing voltage about 3,11v .. is this normal ?
- standby (purple) showing voltage about 4,99v
- bulb glow dim and off

measure test with shorting ground to ps-on :
- 1 cdrom + 1 fan connected
- ps-on (green wire) showing voltage about 3,11v
- standby (purple) showing voltage about 4,99v
- bulb glow and dimming glowing .. it that indicate there is still a problem ? (for about 2second i power off the switch, safety first if there will ake a problem)

after digging some information here ..found this comment from another thread :

Originally posted by momaka View Post

Generally the TV won't be able to do a full power up with the light bulb in series. The light bulb trick is only good to see if everything is okay initially (i.e. the PSU doesn't blow up parts after a major repair).

It's normal for the light bulb to light up for a second or two after you apply power, but if the bulb stays lit, you still have a problem somewhere. For PSUs with APFC, the bulb may cycle ON-and-OFF very rapidly for a few seconds. This is normal. However, if the light bulb doesn't dim or turn off, you have a problem.

Originally posted by Th3_uN1Qu3 View Post

Power supplies with APFC won't like the series lightbulb trick. If the bulb only glows weakly (no shorts anywhere) try plugging it straight in and see if all voltages come up.

Alternatively, you can bypass the whole active PFC section, by temporarily soldering a bridge rectifier to the primary capacitor. Then wire the AC input cord to this bridge rectifier. You can use the series lightbulb here (not only you can, it's recommended that you do). This way you can find out if the power supply itself is alright.

Originally posted by Khron666 View Post

5V stand-by = the purple wire in the 24-pin ATX connector. It should be up and working the whole time the AC is plugged into the PSU, whether it's turned on or not.

+5v/ +12v = ATX standard says they should be at 5/12v, +/-5%, so 5v should be between 4.75 and 5.25v, and 12v should be between 11.4 and 12.6v, to be in spec.

If your multimeter doesn't have auto-ranging, then setting it to the 20V (or 40V?) range should be fine.

PS: I don't have a PSU tester, i do all my testing "hands-on"

As far as i can figure, any half-decently designed PSU should be stable (enough) with no load - that's what the minimum load resistors inside should be taking care of.

Plug in AC though a "bulb tester", check for 5Vsb. With active PFC's, the bulb trick doesn't work that well for "ON" testing - it's gonna light up quite well, and the voltage on the main cap(s) won't be anywhere near 380-390v DC, but for a few seconds at a time, it should do. Next step, bite the bullet and skip the series bulb

so .. its safe to bypass the series bulb trick ..and directly connected to wall socket ? any advice ?

**senz_90** · 02-02-2014, 08:10 AM

Re: repair seasonic p860 with burnt/crack mosfet

"For PSUs with APFC, the bulb may cycle ON-and-OFF very rapidly for a few seconds. This is normal. However, if the light bulb doesn't dim or turn off, you have a problem."

from my experience.
makes sure your bulb OFF, this means no shorted anymore and okay to leaves this psu on without bulb. you said that your bulb OFF or just lit dimly when jumper the PS ON? how about other rails voltage? 3.3V, 5V, and 12V? I think 5VSB will not coming if your PSUs still has a problem

**holmes222** · 02-02-2014, 08:23 AM

Re: repair seasonic p860 with burnt/crack mosfet

when jumpered with ps on ..the bulb lit dimly and then cycle on-off rapidly , but i switch off after bulb gets on-off cycle (about 2second) .. i'm afraid if there still a problem an make KABOOMM in my room

..or its safe to wait when the bulb cycle on-off rapidly until its completely off ? for 5-10second maybe ?
i know if the bulb always lit not dimmming .. there still a problem , correct ?

**senz_90** · 02-02-2014, 10:15 AM

Re: repair seasonic p860 with burnt/crack mosfet

maybe the wattage for bulb didn't enough. i don't know exactly.. hear others advice.

from momaka post psu with apfc it is normal to have cycle on off for bulb.
since you get 5vsb i dont think your psu has shorted anymore. just bite the bullet

and connected without bulb and i am sure that's fine. bulb trick just to indicate shorted or no. but up to you and maybe wait for others advice

**holmes222** · 02-03-2014, 01:56 AM

Re: repair seasonic p860 with burnt/crack mosfet

test directly to the wall socket .. no series bulb .. result is mcb meter went down
unplug everything ..test again with series bulb (with not shorting green and black wire) .. result is bulb fully lit not dimming, indicating a short overthere ..5vsb not coming at all ..fuse not blown
where i mus start checking the short component ? diode/transistor ?

**senz_90** · 02-03-2014, 02:45 AM

Re: repair seasonic p860 with burnt/crack mosfet

fiuhh. it looks like your problem have to apply more effort. i am sorry. from fuse didn't blown maybe it just partial shorted, you must digging into deep troubleshooting way now. just trying measure with resistance reading surrounding components with this mosfet and maybe the fet fryed again.

**holmes222** · 02-03-2014, 02:40 PM

Re: repair seasonic p860 with burnt/crack mosfet

removed the heatsink and mosfet
4 x 6r190c6
2 pair in back to back indicating a short mosfet with diode test dmm
any advice a proper way to test them?
at which point i must start to measuring?

Attached Files

**senz_90** · 02-04-2014, 05:06 AM

Re: repair seasonic p860 with burnt/crack mosfet

this. http://www.bestelectronicarticles.co...g-mosfets.html

**holmes222** · 02-04-2014, 05:28 AM

Re: repair seasonic p860 with burnt/crack mosfet

high res picture of the board
i hope will help much better in circuit analysis for other member here

Attached Files

**holmes222** · 02-12-2014, 01:58 PM

Re: repair seasonic p860 with burnt/crack mosfet

update ..
replace the pair mosfet and soldered in place again, other pair is tested ok
test with dim bulb ..result OK
test directly to wall socket ..result OK
its alive ...

measuring voltage 12v,5v,3.3v .. result OK
test with complete system, went smooth no problem
but ..
after 10 minutes operating, the mcb meter down ..psu wont power on again
disassembly ..measure mosfet replacement ..all shorted between gate-drain-source ..wth whats wrong again ??

only last 10 minutes normal operation ..and then shorted all mosfet again !!!!
dim bulb test result full bright .. definitely shorted

any advice ?

because if i relace all four mosfet switcher , maybe it will operating normal again ..but for how long ?

which component i must check ??

Attached Files

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