My pc100 does not start

[Drack]

Hi guys it me, again... My PSU don't want to start, it has 5vsb, I already took the mov out and changed the fuse because both blew out, I think the 3.3v rectifier (cep603al) is dead because I can read 90 ohms of resistance between orange and ground, when I took out the rectifier, the short went out

[stj]

Re: My pc100 does not start

if it blew the fuse, it probably has shorted primary transistors.

[Drack]

Re: My pc100 does not start

No, they are not, but i measured the primary cap and only 160v DC are coming

[Drack]

Re: My pc100 does not start

There is 5vsb and when I turn the PSU on, it would shut itself off after half a second

[stj]

Re: My pc100 does not start

the optoisolator looks like it had a flashover at the end facing the metal shield!

[PeteS in CA]

Re: My pc100 does not start

That 90 ohms from +3.3V to ground might be a 91 ohm (or 90.9 ohm) preload resistor. That's a flyback (probably discontinuous) design, and such designs often need some preload. The dissipated power would be about 1/8W, so a 1/4 watt resistor would be easily adequate.

[Drack]

Re: My pc100 does not start

It's a plastic sheet stj, the camera makes it look metallic

[CapLeaker]

Re: My pc100 does not start

sounds like the PWM is dead and a major event has happened. As stj already said, that usually goes with something blown up in the primary. However since you have 160V on the main filter cap, the FET should be o.k. What is printed on the PWM?

[Drack]

Re: My pc100 does not start

It is a kia339p I have a aZ339p and utc339 on the shelf

[CapLeaker]

Re: My pc100 does not start

that's a voltage comperator, not a PWM. I am looking for the smaller IC with 8 legs next to the large main filter cap.

[Drack]

Re: My pc100 does not start

Pete, when I took the rectifier out the resistance went up to 3200ohm I think

[Drack]

Re: My pc100 does not start

It says uc3142p

[CapLeaker]

Re: My pc100 does not start

maybe a UC3842? See if the PWM has proper Vcc (pin 7)

[Drack]

Re: My pc100 does not start

It has its 8 pins(weird) this PSU is at 25 bucks on eBay lol

[CapLeaker]

Re: My pc100 does not start

anyway... see if the PWM gets proper Vcc voltage on pin 7. If not, it may either be in under voltage lockout, or the dropping resistor feeding it went high in value. Other than that, you can try changing it out, or buy for 25 bux another one from flea-bay.

[Drack]

Re: My pc100 does not start

I already have another PSU lol, and 25 bucks is what you won on 3 months over here on average I will check tomorrow its almost 23:00 over here, thanks for the help

[Drack]

Re: My pc100 does not start

¡Happy new year guys!

[Agent24]

Re: My pc100 does not start

Fuse might have blown because of a bad MOV, or maybe the MOV blew from a voltage spike and blew the fuse. A spike may have damaged something else too.
But not sure where the MOV is you speak of, I only see two Y-Capacitors and neither looks bad.

Switching transistor might have shorted but then burned out and gone open-circuit afterwards. There doesn't need to be a heck of a lot (if any) outward signs of this on the component body either (although there usually is)

That 8-Pin PWM controller does look like it has a hole in it.

[sam_sam_sam]

Re: My pc100 does not start

That 8-Pin PWM controller does look like it has a hole in it.

It sure does look like that IC-chip has a hole in it
It needs to be replaced

[CapLeaker]

Re: My pc100 does not start

I can't tell on that pic if it has a hole or not, but I am sure as heck that the PWM is dead for one reason or the other. Either it isn't getting any Vcc or it's dead.