Help with a car lighter inverter

[Mandraco]

Hello, every one, I'm having a problem with this inverter and don't know where to ask or if this is the correct place to do so. My inverter is a Peak Performance 175watt TailGate inverter with the model No: PKC0BN, it was blowing its fuse as soon as I flipped the switch on. One time I plugged it to the car lighter with the switch on the "ON" position and it blew my car's fuse. I took it apart and checked to see if there was something wrong visible inside, hoping it was some damaged capacitor or a resistor to replace but the caps and diodes were OK. Amid testing some resistors I saw a metal plate holding two transistors to a heat sink near the transformer, so I took the plate out and found a transistor has cracked (I don't know how) so I decided to take all transistors off the board and test them with my multi meter. The hard part have been trying to identify them in order to test them properly and replace them in case it's needed.

I tried searching online for the codes but the codes on the transistors are not found on any codes list I saw (pro electron, JIS, JEDEC, etc) I'm no technician but I like to learn and I have repaired a couple tvs, DVD players, et cetera. Can you help me on this? Is this the right place to ask? Thanks in advance :-)

[diif]

Re: Help with a car lighter inverter

Photos of the parts you want help identifying.
I test 3 legged components with diode mode on my meter. Any that show a short are them further investigated. Sounds like you found what was causing the fuse to blow, check any components connected to the legs.
As always photos help.

[stj]

Re: Help with a car lighter inverter

also check any "reverse diode" on the input - it's intended to blow the fuse if the power is reversed.

[eccerr0r]

Re: Help with a car lighter inverter

I'm also trying to debug an inverter that doesn't work, however its size and PCB traces that go underneath components is very annoying. It doesn't blow fuses, however...

Usually the transistors on the heatsink of these mini-inverters are its "primary" high current/low voltage transistors. Now determining what they were is the trick... The one I have I believe are MOSFETs but they could feasibly be BJTs as well. A well-known TL494 drives them. Perhaps pictures of both sides of the board would be helpful to make an educated guess if they're MOSFETs or BJTs. They should not be that critical.

Does the device still blow fuses with those transistors out? Now, need a 12V dim bulb tester for this

(BTW, my mini-inverter secondary transistors are not on heatsinks as it's a 80W low wattage inverter.)

[stj]

Re: Help with a car lighter inverter

stuff the suspect parts in a component tester - assuming atleast 1 is still good!

[Mandraco]

Re: Help with a car lighter inverter

Hi, thanks to every one for the fast response. I will attach the picture of the two MOSFETs beside the transformer, the one on the left is the cracked one, easily identifiable by the damage. I must say there are three types of transistors in this inverter: 2 attached to the heat sink; 4 are the same shape as those two but I have the impression that they are a different type and there are 8 shaped like half cylinders. I already took 7 off the board yesterday, so I still have one to go. I will upload the pictures as soon as I get home.

@sti: I tested the diodes(glass/ zenner and the black cylindrical ones) removing one lead from the board for each using my multineter's diode testing/ continuity function but I will do it again to make sure I don't miss any. I suspected what you say about the bad diodes making fuses blow, I have seen this problem with a couple of LCD TVs before. As to your suggestion of using the component tester, I assume you're referring to a specialized tool. To clarify, my tools are a digital multimeter, some pointy hooks, soldering stuff like the iron, solder and such. So no expensive equipment yet :-) I didn't studied electronics, just learn as I go trying to repair what breaks at home. So thanks again, I will upload all other pictures a bit later, maybe at 12-3am my local time, current time is 9:20p

[Agent24]

Re: Help with a car lighter inverter

Are there any burn/soot marks on that cracked transistor? It looks to me like the unit was dropped or the heatsink was overtightened or something, and the transistor was broken from physical damage, rather than electrical failure.

[Mandraco]

Re: Help with a car lighter inverter

Agent24, there was no soot or any signs of burning when I took the metal plate covering/ fixing them to the heat sink. The only sign I found is a mark on the plate as if a bolt of electricity made a marking like a very fine line raised with the same metal. It is as if the metal made a cast of the crack on the transistor like they do with plaster, I will upload a picture so you can understand.

For now, the picture below is of the second type of transistor I mentioned earlier, all four of them have the same code written on their case.

[Mandraco]

Re: Help with a car lighter inverter

Here are the pictures for the other group of transistors, the other type I mentioned earlier, the ones with the half cylinder shape.

[Mandraco]

Re: Help with a car lighter inverter

And here is the picture of the plate I mentioned, Agent24. Notice the curved line on the right, it is like raised. If you pass the finger along the surface the line feels like a very fine bump. I said it seems like it made a cast but it could also be residues of the transistor's casing, I don't know. :-/

[eccerr0r]

Re: Help with a car lighter inverter

Picture of the whole inverter board?
Is it still shorted with the transistors out? (individually?)
Looks like it's a standard h-bridge type, I wish I had yours because it looks like it has a lot of through-hole. The broken one I have is mostly surface mount with components on both sides... GRR.

[Mandraco]

Re: Help with a car lighter inverter

@eccerr0r mine is almost entirely through hole components, but there are two vertical board measuring about an inch squared, which have SMDs. I think it even hav some ICs on those. I will check and upload a picture of the board.

[Mandraco]

Re: Help with a car lighter inverter

@eccerr0r I forgot to address your first reply. I don't think the fuse will blow without the transistors since they are needed to complete the circuit in my opinion. I will check, though :-) About your case, I don't know what to do to certainly fix your inverter but you can trace the circuit, I don't know if that is a term, lol. I just try probing for continuity from the negative cable of the power cord on the board. About the traces giving you a hard time, I used to get the board over a glass table, then put a led light potent enough to get like an X-ray view of the board and take a picture or a couple of them closing up on parts of the board dividing the board into sectors so that you can focus on a sector at a time. It's sort of like making a jigsaw puzzle. Then start from the power source checking the traces and components for continuity until you find a place where the circuit is open or find a short. You can also use the pictures to make a drawing of the circuit and mark where you think there is possible root of the problem. I used to do it like that, drawing but I had no camera, only looking at the board and drawing.

Again, I have no formal studies on electronics and just tell you what I would do to find the problem with the limited knowledge I have.

[eccerr0r]

Re: Help with a car lighter inverter

if it won't blow anymore (use dim bulb tester!), then indeed likely one of the P55NF06 MOSFETs are shorted. See if the gate is shorted to the drain or source (gate is on left, drain is center, source on right -- be careful, MOSFETs are static sensitive.) These could cause the fuse to blow right away if it's shorted. I would think the IRF630B shorting out could also blow fuses but I'd suppose it take a few seconds to blow the fuse.

My mini inverter doesn't have a reverse-power diode, oddly enough.

Looks like all of the "half cylinder" TO-92 devices are transistors except the one marked 78L12, which is a 12V regulator. However these devices are low current and likely fine.

[Mandraco]

Re: Help with a car lighter inverter

I was trying to identify all the transistors in order to find how to properly test them. It's just being cautious, I tested resistors and diodes already but I'll test diodes again, though.

[eccerr0r]

Re: Help with a car lighter inverter

A transistor tester is helpful but not necessary. Having an ohmmeter with diode check should be sufficient to test the mosfets.

If you temporarily short all the pins of an "n-channel enhancement" mosfet (both IRF630 and P55NF06 are n-channel enhancement mosfets) together and then test with an ohmmeter, you should find that all three pins should be infinite resistance to each other - with an exception if you connect the positive connection of your diode checker to source (right hand pin) and the negative connection to the drain (center pin). In this test you should see a diode drop - around 0.5 volts on the diode checker - if it's good. If it's also 0 volts, the body of the MOSFET is destroyed and should be replaced.

Before each trial test, ensure you short the gate (left) and source (right) together to turn the MOSFET off. The gate is so sensitive that it may turn on using your ohmmeter/diode checker which will throw off your open test. That being said, if you turn on the mosfet, then source and drain should short together in both directions, indicating a good transistor.

[Mandraco]

Re: Help with a car lighter inverter

OK, so I need to follow your instructions on the MOSFETs and post the results. I searched online before starting the thread and learned these two transistors are N-channel and remember reading about the test you instruct me to perform, it seems to me that the same test will not work with the other transistors, at least the ones marked "FM H04 IRF 630B" Am I correct?

Below is a picture you requested, the complete board. Not shown are a few diodes en the other side and the peripheral boards for stuff like the switch, power LED, USB ports, et cetera.

I will get back after the tests with the results.

[eccerr0r]

Re: Help with a car lighter inverter

The IRF630B are also N-channel enhancements and should generally behave the same way as the P55NF06, so yes the same tests should work on it.

The other TO-92 devices are not MOSFETs so the same tests do not work, especially the 78L12 which is an IC. For now, assume that thing still works. The other devices are a mixture of npn and pnp bipolar transistors. You can get a quick check on them by simply sticking your multimeter in diode check mode and see if there are any shorts (anything less than 0.1 volts). Each of these transistors should read something of 0.5 to 0.6 volts on two sets of pins (B-E and B-C) depending on polarity (npn or pnp). All others ways of hooking it up should return infinite/open.

and again I hate my little inverter... double sided PCB with smt. At least on a single sided board there's no tracks (or #&*@ vias) underneath parts...

[eccerr0r]

Re: Help with a car lighter inverter

Oh... please check this... Once I had blew my car's fuses when I plugged something in my lighter socket... because the PLUG was shorted... so don't go tearing too far until you check the simple stuff!!!

[eccerr0r]

Re: Help with a car lighter inverter

I pulled the transformer out of my inverter (since it's the biggest obscurement of seeing anything, much like how people tend to pull heatsinks from PSUs... alas no heatsink to pull...) so I could see more crap in this extremely tiny surface mount POS. Interesting.

Seems the power good LED depends on the primary oscillating and not the other way around as I thought it was. Back to the drawing board *sigh*