Help with LKP-0P023 REV0.3 PSU

[cheeky2]

I am trying to identify D7 on this power supply board that Q5 MDF9N50 mosfet R53 22ohm and R54 47 ohm and the IC2 FAN7930 have all failed. I have managed to work out these from looking on the internet.
However D7 I have seen no mention of the value of it so anyone with one kicking around could you let me know the designation of the markings on it please?
Hopefully someone has one laying around that can give the value of it.
I know ohms supplies have a kit056 for it however for the price of the kit I can get a whole working unit delivered for less!
I have all the other failed components available besides the D7 I suspect it may well be a 1N4148W diode but just wish to ensure I get it right!
Just noticed the R57 0.15ohm has also gone as well (not surprising really).
Thanks in advance for any help.
See attached pictures of location of the diode (at least what's left of it!).
Regards Anthony

[lotas]

Re: Help with LKP-0P023 REV0.3 PSU

According to the datasheet on FAN7930 there is a diode just 1N4148 (W) marking (A2, T4), so put it on and don't worry.

[cheeky2]

Re: Help with LKP-0P023 REV0.3 PSU

Thanks for that I thought it was a 1N4148W diode but couldn't find any sheets that related to it with the FAN7930. I will give it a go soon as just have found a 2watt 0.15watt resistor to replace the R57 that was open circuit.

[cheeky2]

Re: Help with LKP-0P023 REV0.3 PSU

For anyone interested here are a few of the parts that blow on these psu's:
F1= T3.15A slow blow
R1= 4.7 ohm
R52=680 Ohm
R53= 22 ohm
R54= 47 ohm
R56= 10k
R57= 0.15 Ohm suspect 3Watts
IC1= GR8876A Substitute using LD7575
IC2= FAN7930C though you can use any variant ie FAN7930B
Q1= 2N3906
Q5= MDF9N50
Q6= JCS2N65F
R35= 0.3 Ohm suspect 2Watts
D7= 1N4148W
If I find anything else then I will update the list.

[cheeky2]

Re: Help with LKP-0P023 REV0.3 PSU

Finally repaired this psu as also Q2 had also gone as well.
So parts list for anyone interested is as follows:
F1= T3.15A slow blow
R1= 4.7 ohm
R52=680 Ohm
R53= 22 ohm
R54= 47 ohm
R56= 10k
R57= 0.15 Ohm suspect 3Watts
IC1= GR8876A Substitute using LD7575
IC2= FAN7930C though you can use any variant ie FAN7930B
Q1= 2N3906
Q2= PMBT3904
Q5= MDF9N50
Q6= JCS2N65F
R35= 0.3 Ohm suspect 2Watts
D7= 1N4148W

[elviramjw]

Re: Help with LKP-0P023 REV0.3 PSU

Looking for values of r31, r32 and r33 on this lkp-op023 pcb

Around IC1

Thnx

[cheeky2]

Re: Help with LKP-0P023 REV0.3 PSU

Just checked I did take some pictures of the area when repairing the psu when checking out the resistors for possible failure so you may well be lucky with the images.
The power supply has now been sold so I can no longer check on the psu.

[jaycee1980]

Re: Help with LKP-0P023 REV0.3 PSU

About to do one of these myself.. the 68uF 450V primary cap was bad, F1 and R57 are gone, not sure about Q5. IC1 seems to have survived (at least the top hasnt blown off of it!)

I'll be checking the rest of the supply works first - i have a 100uF 450V capacitor, and this first stage is a PFC so it can be bypassed. If the rest of the PSU is shot, there isn't much point in attempting a repair I think.

I wish they'd build protection into PFC controllers so that if the cap fails, they dont just drive the MOSFET on hard, causing this type of failure! So bloody common...

[jaycee1980]

Re: Help with LKP-0P023 REV0.3 PSU

Sure enough by bypassing the PFC, this one appears to work ! Q5 is dead though, and I found R53 was open so I suspect the PFC chip has bought it as well (just didn't blow its top off)

If anyone wants to try bypassing the PFC to see if the rest of the supply works, do the following:

Remove R57, Q5, L2, D1
Remove R22 (might not be needed, but best to keep the PFC out of it if the chips still there)
Fit wire links at J3 and D2

Oh, and fit a new F1 and E2 - this is usually why the PFC exploded in the first place ! Bloody CrapXon junk!

[cheeky2]

Re: Help with LKP-0P023 REV0.3 PSU

Sure enough by bypassing the PFC, this one appears to work ! Q5 is dead though, and I found R53 was open so I suspect the PFC chip has bought it as well (just didn't blow its top off)

If anyone wants to try bypassing the PFC to see if the rest of the supply works, do the following:

Remove R57, Q5, L2, D1
Remove R22 (might not be needed, but best to keep the PFC out of it if the chips still there)
Fit wire links at J3 and D2

Oh, and fit a new F1 and E2 - this is usually why the PFC exploded in the first place ! Bloody CrapXon junk!

Thanks for that information if I ever have one of these go again I will try it out.
Originally I just used a cheaper used different model psu I believe it was a Technika psu model that had all the outputs for a third of the cost of these psu's. As the ic for the repair was coming from china so the wait would have been too long and had it lieing around getting dusty for me to repair when I had the time!