Dell model L275E-01 pn: Wu142. Optiplex 755 small form factor.

[momaka]

Re: Dell model L275E-01 pn: Wu142. Optiplex 755 small form factor.

you have my interest though - what reddish brown thing???

I think he's referring to the polypropylene/film cap (behind the bridge rectifier, on the lower left corner on the PCB in his picture.)

The thermistor should be that green disc component next to the square light-blue X2-cap (or is that a relay?)

That said, if you feel comfortable with working around line voltages (warning: this could be very dangerous if you're not careful), try measuring the voltage across the primary electrolytic input cap with the PSU plugged into the wall. It's located on the upper-left corner of the PCB, next to a large toroid. The voltage should be either somewhere around 160-170V DC if you have 120V AC line voltage (which you should since you are in Canada) or 340V for Euroland and countries with 220-240V AC line. Let us know what voltage reading you get on this cap. Again, be very -CAREFUL- while doing that measurement, because you will be working around line-connected components (shock hazard!) In particular, do not touch any of the PSU parts (especially heatsinks) while the PSU is connected to the wall. Also advisable you wear safety glasses, should you happen to short something by accident, which may result in solid state components to blow up and throw fragments towards your eyes/face.

[stj]

Re: Dell model L275E-01 pn: Wu142. Optiplex 755 small form factor.

no, your not.
the thermister is green with a rough finish - it may be hidden in heatshrink.

you have my interest though - what reddish brown thing???

[Jackching]

Re: Dell model L275E-01 pn: Wu142. Optiplex 755 small form factor.

+1

Since this is an APFC unit, first check the input fuse for continuity, along with the input inrush NTC/thermistor. If the APFC is faulty, one of those usually goes with it.

If these are both fine, you probably have bad caps causing the 5VSB to misbehave. I see lots of blue Ltec caps, and those are known to be very problematic. Can often go bad without any visual signs too. So for this reason, I now replace all Ltec caps on sight.

Tested the fuse and caps which all read good. The thermistor is what I'm unsure of. There is a big reddish brown one there and a couple of blue ones if I'm looking at the right components.?

[momaka]

Re: Dell model L275E-01 pn: Wu142. Optiplex 755 small form factor.

how's the fuse?

+1

Since this is an APFC unit, first check the input fuse for continuity, along with the input inrush NTC/thermistor. If the APFC is faulty, one of those usually goes with it.

If these are both fine, you probably have bad caps causing the 5VSB to misbehave. I see lots of blue Ltec caps, and those are known to be very problematic. Can often go bad without any visual signs too. So for this reason, I now replace all Ltec caps on sight.

[stj]

Re: Dell model L275E-01 pn: Wu142. Optiplex 755 small form factor.

how's the fuse?

[Jackching]

The computer wouldn't turn on this morning. No visual signs of bad components. Can't get the diagnostic light to even come on. Has anyone worked with this unit?