I have made sure a fan was present (load) on the peripherals lines to ensure I would be alarmed at any changes while working.
1. Why not draw a schematic of what you have traced so far starting at the AC mains?
2. I would pull the data sheet on the PFC IC and see if you can read about what control and monitoring inputs it has and what its expected behavior is.
If you have gotten to the point of discovering that ICs model number and it has a public data sheet in a suitable language anyway.
3.When you say you measure a certain voltage I am not sure if that is true RMS or non-RMS AC or peak or what. If you had / have a waveform or more details than I have seen so far that might help.
4. Also we should know what your line voltage is in relation to the measured or displayed rectifier output.
A 100VRMS line sine wave voltage will have 100*sqrt(2) = 100 * 1.414 volt positive and negative peak magnitudes because the crest factor of a sine wave is sqrt(2) times the average value. I am not 100% sure what the RMS value of a full wave rectified sine is, but logic tells me it should be the same as the line RMS value since energy / voltage is not being lost if the rectification is perfect. Logic also tells me that the RMS of a sine that has half the peaks cut out by half wave rectification should be half of the RMS of the input voltage because half the signal is missing. So depending on your line voltage and your DVM you can tell if your readings are as expected. If your DMM measures frequency of mains signals safely then of course full wave has twice the nominal line frequency while half wave has half and unrectified mains has the nominal frequency.
The PFC unit should either be along the left side or along the right side of the top of the PCB in the first post photo.
Then there is the PCBA off to the left side of the photo of the bottom side of the main board in the first post. Where did that come from?
Could be a bad diode, coulld be just something that is supposed to beeeeee in parallel with it for some reason.
PFC refers to pre-rectifier bridge(full)/DC conversion?
PFC stands for power factor correction. For most of the time, it is essentially a boost converter with current-voltage cascade control loop. It controls its real time current to track AC input's voltage, and it controls its average current based on output voltage.
The 168V clearly shows it is not working.
1. Basically something in the over 300V but under 400V range is usually some indication that the PFC is outputting a boosted value. What is the peak of your actual mains voltage? Do you know?
I don't know if you're in Japan or UK or whatever could be as low as 90VAC up to 240VAC.
2. The PFC input would be something like full wave rectified mains voltage, and the PFC would implement a boost converter to boost the PFC VIN FW sine rectified pulsating DC waveform up to the DC bus peak voltage around 350V.
3. The secondary of the main transformer is not 12VDC or 3.3VDC directly but probably something that is somewhat higher than 12VDC as an AC signal and which is then synchronously rectified and filtered to make 12VDC from that. Depending on if it is a full bridge or half bridge or LLC or forward converter or whatever determines the waveform of your primary and secondar. There could be additional secondary and primary side windings as well.
Multiple secondaries if present may or may not be able to provide voltages that can be used to efficiently derive +12V, -12V, +5V, -5V, +3V, etc. ratiometrically relative to the just over 12VDC AC equivalent most important seconary output.
Additional primary windings can be used as a bootstrap / power supply winding to feed back and supply a suitable voltage maybe in the range of 5V to 40V to the PFC converter IC that needs to be powered by something, usually in the 15V-20V or so range maybe depending on implementation.
So a defective power supply for the PFC IC could also result in PFC failure.
So you have no oscilloscope and safe way to use it and appropriate probes etc. measure mains related signals with it?
WHERE did you measure the 169V? I was hoping for some little bit of a schematic up to the PFC input.
169V across the 400V main DC bus storage capacitor means the PFC is not operating to charge it.
169V across the mains rectifier going into the PFC before the boost coil is probably normal.
1. Also isn't that another IC I see on the back side of that same board that should be more visible? What is that?
2. Is that a DIP packaged chip? Looks like it has more than 4 pins on a single side of the package so more than 8 total for that IC?
3. EDIT: Please see the edited version of my post with various images of block diagrams above, I added an annotated one that should show the flow and be hopefully able to be related to the circuit you are seeing in generality
PFC IC?:
I would first try to find whether the PFC circuit is dead, or the secondary side didn't signal the PFC to start at all.
As I said before, probe the optocouplers. One of them should be connected to that PFC controller daughter card.
While powered on (with green wire grounded), use your DMM to measure the input side of the PFC opticoupler (input side means secondary side, not mains input side, for this particular optocoupler).
*I assume you know what you are going to do. Slipping your finger and touch mains side while powered on can and will give you a nasty pick-me-up, or worse, put-me-down, so practice your best cautious, or better, solder a pair of wires from optocoupler to your DMM's test leads, and stay away form it.
To me, it seems like U3 is PFC control optocoupler.
Power on the system, short green to ground, and probe input of U3 (the pins on secondary side), tell me the voltage.
It should be ~1.2V, give or take, for a working PSU. If its voltage is very low, almost zero, then your problem is on the secondary side.
To me, it seems like U3 is PFC control optocoupler.
Power on the system, short green to ground, and probe input of U3 (the pins on secondary side), tell me the voltage.
It should be ~1.2V, give or take, for a working PSU. If its voltage is very low, almost zero, then your problem is on the secondary side.
I would assume it more likely that some issue that will not involve replacing the PFC IC or module would be more likely.
I think the thing to do while the system is apart is to
(a) Inspect it.
(b) trace it to know the most relevant connections
(c) identify / arrange possible points of in-system test access to relevant nodes so you can check the states at run-time
(d) perform any individual component or sub circuit testing that seems possible and necessary.
Otherwise soon I think you should put it back together and then identify the operational voltages at the control and signal nodes that you will have identified so you can determine a cause of why the PFC has no output.
Then, having established the circuit input that may be at fault, look for a way to prove / repair that aspect.
Corsair CX500 PSU Repair - YouTube