This is a boosting switch mode power supply that runs on 12V and outputs approx 300VDC. The 240VAC is created by fast switching the 4 mosfets or groups of mosfets in an H-bridge. Some filtering, smoothing and safety is added. And that's it. To repair: Remove the mosfets. Check them. If one is damaged, order new ones from the same batch for all positions of that section. They should be balanced. Now first, clean up burnt areas, resolve shorts, replace parts that are obviously broken, check small transistors, check the gate resistors, and all other small stuff. If you have one, then connect a 2-channel oscilloscope to the gate connections of both mosfet groups and power up the device using a current-limited 13V supply. You should briefly see nice drive signals, just before the protection powers the thing down again. Turn it off. If you don't have a scope, you can use a good AC multimeter that does not show DC components when measuring AC. Check that by measuring a DC voltage in AC setting. It must show almost 0V. So, at the gate connections you should see an AC voltage, indicating that there is a drive signal. If that is all working, for both mosfet groups, then we can proceed. Now, at each group, you mount one mosfet, so you blow up max 2 mosfets during testing. Connect a small test load and a multimeter to the main capacitors at the secundary side of the transformer: at the main capacitors. Test load can be the two of your smallest 240V incandescent light bulbs in series. Stand back and power up again, briefly. Your test lights should light, and your meter should indicate a significant DC voltage in the capacitors. If not, try again and take attention to your power supply. It might get overloaded by this. In that case, you'll need to use a bigger power supply or a battery. when using a battery, then use a smaller fuse while testing: 10Amps. So... You can proceed with checking drive signals at the high-voltage part. During this, you leave the light bulbs connected. They will discharge the capacitors fast, between every test you do. For safety. Here we do the same: before actually mounting mosfets, we first measure if drive signals are present at the gates. When all good, you can also mount some mosfets at the secondary stage. Connect another small incandescent light bulb to the output and test again. When you ordered your mosfets from China, you should test them before mounting them. If all good, remove the test mosfets and mount all new mosfets. At this point, test again. If all good, remove your test light bulb, reassemble, install the correct fuse(s), test again with a battery and a bigger load. These units can fail with a lot of damage. A mosfet usually fails into a short circuit. That kills the mosfet at the other side, too, probably in a short circuit as well. So now your 12V supply is short circuited. Hopefully, the fuse goes out before the tracks burn off the circuit board. Failing mosfets will often feed quite a lot of current into the drive circuitry, killing that off as well. So, if you just change the mosfets, you're setting yourself up for some more dead mosfets. If your brother uses power tools on these units, you might want to add some more filtering to the output. Add a capacitor of the type you find in those fake power-saving plugs. Thank you for reading until the end.

The process should go -> fuses -> transistors -> diodes ->caps -> resistors -> ic. The cracked component is optron (opto couple probably PC817). Check for shorts on all of the parts and then check for improper open, bulgy caps, diodes should show something only on one side. You can't change zener with diode, those are two different components. Diodes are fast recovery so they should read 150-400, transistors read around 500-600 according to base to colector and emiter and not on other direction. MOSFETS can retain their state because the Gate acts like capacitor and can charge and discharge Source - Drain conduction. You CAN'T test MOSFETS in diode test, you have to charge the gate and discharge it and measure it like switch (or potentiometer) who is controlled by the Gate. Resistors can go open or higher on resistance. Don't change 0.5 Ohms with 15 Ohms, those are current sense resistors, the device can go in current protection mode if you do that. Multicomponent tester that you have should test MOSFETS and show if they are within specs. You can damage MOSFET with static discharge. YOU HAVE TO CHECK ALL COMPONENTS BEFORE TURN IT ON. USE REGULAR LIGHT BULB IN SERIES WITH INPUT CABLES to prevent blowing the components in case of shorts.

When your brother asked if mosfets have "memory" or if they latch, yes they do, sort of. A "latch" device like an SCR will stay on until all power through the circuit drops below a certain threshold. Mosfets can certainly hold their state outside of circuit, basically by charging the gate. Remember the gate of a mosfet is similar to a capacitor and it holds a charge. For example applying a momentary positive voltage (with respect to the source) to the gate of an enhancement mode N channel mosfet will turn the mosfet on and it will stay on until the gate is discharged (typically by connecting the source to the gate).

Very well done to be someone that actually says there not hard up and that nothing will be put behind a pay-wall and only pay if they can comfortably. Appreciate the honesty also keep up the good videos 👍👍👍

A lot of inverters will make that squealing sound if the input voltage from the batteries fall below around 11.5 volts D.C. . check the input battery voltage before you connect the inverters and then once the inverter is on and see how much the battery voltage drops and if its below 11.5 volts or so that may be one of the reasons. Also the output transistors as well as the pwm mosfet driver ic often fails along with the input and out put transistors so you pretty well need an oscilloscope to see if there is an output from the driver ic. I love these type of switching power supply type of videos, please do more if possible.

I have a advice for you. Every time you want to power something for testing. Please use a bench powersupply with current limit function, it will protect the components on the device from blowing up. Inverters like these only require about 2amp to produce the required output voltage with no load , so by using a for testing you can safely test the device at low currents without having to use a big lead acid battery and shorting it out and harming it.

Thank god trying to fix is still going to be around, these are the best videos

Suggestion: When trying to fix "Blows-the-fuses" stuff, try replacing the fuses with an appropriate-voltage incandescent light bulb for test. The bulb will actively limit current to non-destructive levels and allow powered testing. I'd use a 12-volt auto headlamp for the inverter, for instance; and a 75-watt 220V(Europe) or 110V(US) for a small tube(valve) radio. A 50-watt lamp should be suitable for most line-powered solid-state stuff. Just wire the lamp in series with the line and use appropriate cautions of course. The lamp power should be about twice the power rating of the device under test. Good Luck and thanks for the excellent video series!

Patreon plug....very honest representation of your situation....nice to hear....good for you

Really interesting. Looking forward to the revisit! P.S. Thank you so much for the mention, Vince. 👍 I'm heading over to Patreon now to support you.

At least we got green lights. Very nice. I think they are very hard to fix but it was very entertaining. Thanks.

Car batteries are 12.5v+, even close to 13v fully charged. That thing probably thinks your "battery" is dead when you give it 11.96v with those thin wires

5 amps will run a vacuum cleaner and microwave oven so 5 Amp is quite a bit. When I was a truck driver I had a full desktop computer with a CRT monitor that I ran on a 600 watt 120V power inverter.

I surely admired your endurance towards fixing a thing. No many human has that quality. Looking forward for more such video. Keep it up.

Love your honesty.

51:12 12V batteries measure about 13.8V when charged and 11.9V discharged so that inverter is reading undervoltage when you feeded it with the PSU. Check the voltage on that battery and you'll see.

Having a blown apart opto-coupler is certainly a bad sign... you made the right choice there to do the shorted unit.

Sooo happy to hear your finally on Patreon! Love your videos and can't wait to support you and your efforts! Thank you for videos Vince!!!

transistors have Base Emitter Collector, MOSFETs have Gate Sorce Drain

I always like to watch such a video. Although there is a failure in repair. It's a pity that I didn't have popcorn but only coffee to watch the video. I'm glad you have the Patreon. Of course I was waiting for it and I'm already a member. I hope this helps and I will have something to look at, learn and admire skills

This is my favorite, when your brother help you with fixing things you explain and talking about your fix in a really entertaining way! Love it thank you!

I would order a few bottles of "Magic Smoke" to replace that which you have let escape. 😂😂 Thanks for the entertaining video. Electronic repair is fun and often frustrating.

Welldone vince . Honestly is come first. That why i love you videos. God bless you

the blown mosfets are part of H matrix circuit which generates the output sin/modified-sin wave AC. The 4 mosfets should be of the same number and same patch, that's critical most of the time. In my estimation, the DC 12 to 240V DC is probably ok that can be measured with H-matrix mosfets not installed. BEWARE the hugh capacitors will be charged with 240V DC. Discharge them by connecting them to 240V lamp. If that part ok, then you can check the IC circuitry is pulsing the H-matrix transistors correctly. you'll need a scope for that. BTW try to put a 2.2ohm 10W resistor inline with the battery positive to avoid fire in case of a direct short. The last inverter is beeping because the output voltage didn't get up in time.

They are designed to run with the engine running or a fully charged battery same as Ham Radios they don't like to work below 12 volts and even that is a little low for some things. Mate keep up the good work I will give more likes since that is what I can do

your brother is right, the fuses would blow sooner as 25 amp rather than a 35 amp and 40 amp. as for the noise it is an indication of low battery current or voltage. I have had it happen on my inverter, and works fine after running the car engine for a few seconds, and letting the engine power take over, plus also after giving the car a run it works fine.

Paul is to My Mate Vince what Ralphie is to BigCliveDotCom. Perhaps your brother needs a home tripod and lighting for when you visit...

You can use a light bulb in series with the fuse block while testing blown fuses. Instead of a fuse lighting, you will light the bulb with any excess current from a short.

I admire your sheer tenacity and patience.

this comment is to help the algorithm for the my mate vince`s channel .. love ya work vince

You are seriously a good dude. Keep up the good work. Thank you.

A 12V car battery should be between 12.6V and 13.2V fully charged. I wonder if you fully charge the battery if you would get different results

Set your bench power supply to 12.8 - 13.2 ballpark, to simulate a car battery.... I feel like your big battery is also dead... That long beep is low voltage.... I think the smaller inverter works off the battery because it's not pulling as hard off the battery, and he battery is able to hang in there with "just" enough voltage to run the smaller inverter.... But under the load of the bigger inverters, the battery can't hang in, and the voltage drops down and trips the undervoltage alarm.... I feel like, with a properly charged battery, both of the big ones might be working.... You said it yourself... Now they both behave the same.... Heh heh! That's because they're both fixed, and both are hooked to a battery that is discharged.... Which, in that case, both are behaving exactly as designed..... Those things are designed to put out that screaming tone when the battery is discharged... It's trying to tell you, "Hey user! Whatever you had plugged into me, just stopped, because I have no 12v power anymore! " I look forward to the revisit... Nice job.

@22:00 MOSFETs can turn on with the test voltage from the meter, if you reverse polarity on the same pins you can turn them on/off sometimes and get different results. LOL @28:00 never mind, you figured it out.

IC2 is an opto coupler. It is part of the feedback circuit for the voltage regulation or for controlling the phase transient. The big slit in the circuit board is an indicator for that, because this way you isolate circuts from the high voltage part to prevent HV sparks to the low voltage side. MosFets tend to short when they have too high current loads because the silicone forms a permanent conductive channel when the current exceeds the current rating of them. MosFets do not maintain state after power loss. The IRF740C and the JSC740C are interchangeable. The IRF740 is the better part though. The failure might come from the feedback circuit. If the MosFets are not controlled correctly you get the burn out. The issue can be the opto couplers or the regulating IC. You can test the optos in Diode mode. Each pair of pins form ONE diode. So you can test both directions between the pairs.

Parasitically MOSFETs can sort of stay on for a short while as the gates are basically little capacitors, but most circuits have pulldown resistors to turn them off as a failsafe. Also touching the legs with your fingers will drain any charge from the gate, having said that charge on the gate won't stay there for long on its own due to leakage.

Great vid Vince, To answer your question regarding the battery working but not the PSU. You might check the voltage drop on your PSU leads, they look rather thin, just measure the voltage on them while under load, so just hook up a 12v LED strip or something that is going to draw a farily decent amount and use your meter to measure the voltage on the croc clips,, alternatively you could measure the resitance of the leads and calculate the drop....I'd guess theyre dropping voltage, if this is the case you might want to put beefier wires on bannana and croc. It's also possible the battery is also at a higher voltage when fully charged and of course your battery leads are very chunky and unlikely to be dropping any significant voltage. I'll just add, when selecting mosfets, don't concern yourself with selecting the exact same, more often than not your absolutely fine putting in another make/brand provided the current and voltage rating matches or exceeds the max rating of the one your replacing, this is not always the case as there is more variables but in this instance it would be absolutely fine provided the pinout is the same

I think from memory the battery can supply 100A. Even if the inverter could switch on, it would only be outputting a theoretical maximum of 240V 0.5A with the power supply. However it would be lower than 0.5A due to the circuitry of the inverter using some power. On the battery a theoretical maximum of 5A could be outputted but again it will be lower than 5A because of the power the invertor circuitry uses. Looking at the label on the inverter it says 500W meaning it outputs just over 2A. That means the inverter needs just under 3A just to switch on or 6 times the current of what the power supply can deliver. As for the beeping I would suggest that you check the diodes and capacitors on the output stage for shorts and the resistors for being open. As the chip is testing for the voltage and current being right. Since it doesn't see what it is expecting to find it sends the signal to start the beep.

Much appreciated regardless of outcome..

My Mate Vince, If the Donor Inverter fails after you replace the borrowed Mosfets, the failure is due to a miss match of the two replacement Mosfets being either slightly faster or slower, this mismatch is caused by environmental changes, along with impurities within the materials from one batch to another batch of production. Having said that and if the Original Inverters Mosfets are cheap, I would replace all of them, as I suspect this may be the reason why an eventual failure occurred, This miss match has caused one or two mosfets having to do most of the work thus stressing them to their failure, and once they failed, what we had was a cascade of failures ergo taking out one extra Mosfet. If you decide to replace all of them, I would suggest before you power it on, you first check all Diodes, also check that socketed IC for shorts to it's ground pin, if there is a short replace it "The IC" and check components around the IC empty socket for incorrect values to resistors, Resistors should have resistance, if they're open then they need to be replaced, as should any short circuited capacitors be replaced.. GOOD LUCK..

I love when you get your brother involved and included!

Love your trying to fix videos videos.

I'm just glad Vince is still around uploading quality content.

Smaller inverters is like the one better thing about the American electric system

proud to be throwing some change your way Vince, hope it helps!!

Glad to see a patreon I get paid soon I'll be sure to support :D

A good tip if working with low voltage high current device is study ohm's law which will give some insight into resistance of conductors . The leads from your PSU are way to thin to carry the current the inverter needs. They have a high demand as it needs to charge the big caps up on startup. Have worked on many different inverter types and more than few that have gone bang. If you can get a circuit diagram of even just block diagram, but you probably won't get the exact model but one very similar will give some idea what things are and what to look for and where. Thanks for the video.

I felt bad so I didn’t skip the beginning I hope u can do 2 vids a week

I've only got as far as the intro - for now! But one word describes your approach to Patreon - "classy." Great to hear the trying to fix videos are staying as I had thought they were going to disappear!

Next video Vince fixes the world with a bodge wire and a couple of fuses.

That beep is a low voltage alarm or try replacing the chips

Vince Optoisolators are two diodes. One to produce the light, the other to receive the signal back. You can test them on diode test.

Watching the ads all the way through to help Vince

Really enjoying videos vince 🙂

the minute his Patreon pops up... I signed up :) hope everyone else is too!

Check car battery make sure it's fully charged might look up the beeping online it might help you

Vince, about time put up a way to support you! But mate, put it in link and/or pinned first comment. Just the link is enough if that's all you want. You can bulk modify comments and descriptions using Tube Buddy to add it to all you're videos.

Usually what blow the MOSFETs on inverters is a incorrect switching order because they need to alternate between each other to get AC, which means that if one fails to turn off (either because of a short or a incorrect gate potential) then when it alternates it will short out the others.

Great video vince so nice for you to be very honest and not doing a paywall ：）

This is what is known as "shotgunning components" at the fix, and its perfectly acceptable to me.

Vince keep it up man always love your videos you certainly have a special way of doing videos which is just great and you have made me smile and laugh quite a few times too, also I always learn something from watching your videos the longer they are the better I say keep it up will be a sad day when there's no more myate Vince videos.

Check the 4 diodes nearest the mosfets I had same problem and two diodes was open both ways and I should say thank you as it was your video that give me the idea to check my mosfet I removed it and it was bad but still had a short them I check my diodes and two was open out of the 4 of them

Also check the opto-isolators are all good. I have a feeling the switcher feedback is not working. The source of the original issue may be one of the capacitors, so check the smaller caps in the same area.

Search for the datasheet of the DIP IC next to the optocouplers. That should be the controller for turning the high voltage DC to AC (it controls the 4 MOSFETS trough 2 of the optocouplers, the 3rd opto handles feedback). The datasheet should explain what gate driving signals to expect. Then you can try running the device without the MOSFETS installed (and thus without risking damage) and check the signals from IC all the way to the gates. There's probably still something wrong along the way causing shoot-trough.

Thank you for the shout out by the way thats amazing 👏 💜

In a case like this, Instead of a re-visit..you should do a "going to fix" video, meaning you will fix it it or else.. think of how much you will learn.....Buzz

"What a Ride" 👍😎 Thank You - A "differential scope probe" would be a way to more safely troubleshoot a "switching" power supply. But I don't recommend it. 2 Pricey & Dicey IMHO ⚡🔥 🤤 Hey, those MOSFETS were kinda "latchy" in a way 🤔

General rule of switching power supply troubleshooting is: If you have components failing on secondary side, look for a cause on primary side, and vice versa.

Have you tried the beeping one on a running car or a battery on a charger. I have one that isn't like "smart" per say but it will turn off if the voltage dips below 12. It would do the same thing where it would start beeping pretty quickly and wouldn't power the high voltage side.

3 hands with the multimeter, you are as an indian goddess

Oh well....it's a TRYING to fix, you never promised it would be a fix 😁👍🇩🇰

Sounds like a low power noise from battery. It makes a noise so you don’t run battery down

Watching video whilst commenting on my phone, subscribed to both guys as they have what looks like my favourite kind of content. Thanks Vince, on my last comment it autocorrected to Vincent, that was not intentional lol

When you connect the inverter to the car battery shouldn't you connect the Red lead first then the Black one? I was told that's safer

Great video =D Shame they couldn't all be repaired. When you knocked something over at 49:40 it scared the s*** out of me lol! Regards that test at the end - car batteries provide 50 / 100 / more amps etc. 10 amps from a bench PSU just isn't enough.

At 12:00 mins, the transistor near to the big smoothing caps is also had the arse blown out of it

My inverters alarms like that when the input voltage is too low you need to check the 12 volt battery when the red fault comes on it may be low less than about 11.2 volts because car batteries are around 12.6 volt when fully charged.

Power them up in series with a car head light if there's a short it will light up and protect the inverter

Great for an over the road truck driver

Look up the beep codes for the device. All of my inverters alarm if the input voltage is too low. Other than that the onboard CPU is likely detecting a fault in the drive circuitry. No output means it is failing before output voltage is generated. You could put a meter on the output and see if the voltage tries to climb, what frequency it is at, etc.

the 4 diodes which are the bridge rectifier need testing, pull them ALL out of circuit, test them then put them back and test as a bridge rectifier they are right next to the 4 blown mosfet, then text the red resistor thing and any ceramic caps out of circuit, check the diodes feeding the 2 yellow supplies, from memory these are the things that take out fuses and mosfets, after that it can only be the 2 big caps or the 2 yellow supplies, that being said im a noob not a trained pro

Hmm, same fault on both. I wonder is it your battery is not supplying enough power causing the beeping noise?

hi Vince. excellent video. One question: can you hear the screaming from the viewers? please dont stop you are genuine and very entertaining. Good job

22:00 Correct. They do not retain their state, they're like basic switches (very simplified) in that context

Nice to be your first Patreon ;)

Hi pitch whyn is low 12vdc battery power from the old models would complain when current/voltage was low. Sense low voltage the pots might need adjusting after battery fully charged.

Hey guys, buy a 12v 20-50watt incandescent bulb ( in a holder ) and place that in series with the 12v battery If it fuses, the light will come on, but it would limit the current to the inverter preventing bangs

I got my Patreon membership with you.

Regarding your Power supply. Generally these will disable themselves when they detect a low battery condition. the 11.9v would be very low for a Lead-acid battery, so its not enabling the output. 12.6v is a fully charged Lead Acid, so you should be aiming for around there!

150A is about right, these inverters have two ratings, one for startup, one for constant run. This one is probably a 600/1800 or close to it.

This one looks like it could be risky. Love the great work Vince. I've said it before I learn so much more from watching you learn than seeing an expert just running through something start to finish.

Subbed to you on Patreon buddy keep up the great work 👍

Is that battery properly charged? It may not work if the supply isnt high enough.

Haha like the website names at the beginning.

49:41 This caused heart attack man.

Regarding the socketed IC being unusual for a new product - mate, the whole thing is through-hole! However new a product it is, it is an old design.

All 4 output MOSFETs must be same, else a slightly different characteristics can lead to short

When the Mosfets shorted it sent high voltage to the drive circuit damaging it. Also tell your brother to not overload the inverters (he seems have blown a few of them), if it says 600W then use max 300W max. The leads from your power supply will be dropping voltage at 10A, even though you have 12V at the power supply you may only get 9 or 10V at the input to the inverter. keep up the good work.

I think that is a low battery voltage alarm.

hi put up sun panels on her roof she got a big inverter sun panels are ok if you are on a boat did you get them at a cat boot sale as i have seen alot of them around not working