The capacitor you took out is correct and perfectly fine. The 450V cap is for the european 240V AC version, which would see about 370V DC. In your US version, the cap will have about 180V DC on it. The DC voltage will be a bit higher than the peak of the AC output to account for the MOSFET on resistance.
Yes after taking actual voltage measurements I realized the original cap's rating was ok. I show this in the video. My replacement is a high quality Nichicon with the same 220uF rating, just a higher voltage rating which is perfectly fine to use.
Extremely well done. New Subscriber. Quality work - refreshing. Everything clean and organized. No ram/cram/jam ... took your time to do a great job. Looking forward to watching more of your vids, and appreciate the share.
Congratulations for this repair! I think it is also important to mention that, when replacing an electrolytic capacitor, the case may also be at an high potential. For example, TDK says, I cite: " Single-ended, SMD, snap-in, and screw terminal capacitors have an undefined electrical contact through electrolyte or other parts inside the case". So when replacing the cap with another cap of another diameter, the insulation clearance will vary, and it is important to respect the minimum clearance according to the local regulation.
Correct about the capacitor case being at a voltage potential. In this case both terminals of the cap are floating above ground potential. It is good practice to make sure nothing comes in close contact with the side of the capacitor and especially the top of the capacitor which is tied to the negative lead and the top of the capacitor is not insulated.
Nice job. One thing to mention for someone not that experienced: Measuring MOSFETs with a DMM can be somewhat missleading sometimes. The voltage applied to the gate by measuring continuity between gate and source can be enough to make the drain-source Path (partialy) conducting. Touching the gate and source can be enough to discharge the gate again making the MOSFET non-conducting again. In this case it certainly looks like a dead short though. (A good component tester makes it a bit easier to avoid such problems.)
Hi, thanks, and yes I would normally use a component tester to carefully and accurately check a MOSFET but these were completely destroyed. I could tell that something was defective from the short circuit reading as I worked back through the circuit.
That thermistor is very important as it will activate the fan for cooling the mosfets it should be mounted on the heat sink with a clamp . A common problem with mosfets and dud capacitors in inverters
KME is a united chemi-con (or nippon chemi-con - same company) series, and that's the United logo - they're just as good as nichicon. Caps I'd trust are (united/nippon) chemi-con, rubycon, nichicon, and panasonic. They're all top-tier brands (some particular bad series in all of them excluded - even the good companies have had notoriously bad series of caps in the past)
47:08 you can also use HV/isolated probes on a regular scope. They used to be stupidly expensive, but micsig has some reasonably priced options these days - essential for working on the primary sides of switching power supplies, or vector motor drives!
Are there other options for scoping the AC wave of an inverter besides an isolated battery-powered scope? Is there any alternative, or any way to take a wall-plugged scope and isolate at least the current from the inverter to make it safe(er)?
If you want to use an AC line powered oscilloscope with traditional grounding on the AC line you need to use a differential scope probe. This will allow you to probe a circuit with reference to a point that is not at ground potential. Don't float the oscilloscope with an isolation transformer as this is dangerous and will put high voltage on the scope chassis.
@@EriksElectronicsWorkbench a isolated transformer in the scope will not put high voltage in the chassis, it will do only if there is leakage in the scope circuit. And if use another isolated tranformer to power the AC equipament under test the risk not exist.
Isolating the scope from ground creates a hazard when your probe's "ground" connection is at a voltage potential (above or below ground reference) which then raises the oscilloscope chassis above (or below) ground and poses a dangerous shock hazard. Users try to do this when testing switchmode power supplies for example. Isolating the scope from the AC line should only be done if you are actually servicing the scope. I'm currently working on a Tek 2247A and the power supply board has a factory inscribed note to use an isolation transformer when servicing. @@mcac-youtube
I rate this video a "4C" For CLEAR, CONCISE and COMPLETE CONTENT :O) I really enjoyed this last hour. Points for "post editing, staging and follow up tips". You R the "Circuit Whisperer". ʞɔoɹ noʎ
