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Afternoon all,
I have a PJ 5KW V8 LF inverter. I ordered new boards, and mosfets as it quit working and none of the green LED's were lighting up except the mos boards. The only parts I didn't replace was the main board, transformer and charging board.
All the LEDs are on now but upon powering up it says it's overloading and shuts off the power. While it's still running it puts out 110 volts according to my multimeter but it sounds like frying bacon in the transformer.
Any ideas on where to go from here?
Oh dear, that's not a comforting sound...nor a safe one I would say. What is the input DC amps when it's trying to run?
What caused the inverter to blow up the first time? (Might have a major clue!)
"Frying bacon in the transformer"...are you sure there are not little metal scraps in the vicinity/inside the transformer core and/or the tranny isn't in contact with the chassis sides/lid?
Hi Sid, I had it for exactly 5 days and it quit using a 1kw microwave. It had a burnt electrical smell afterwards. No visually blown fets. I contacted the seller who offered to send the parts bit after back and forth for several months I was informed PJ had no parts to send me as they were all being used in production.
I have not checked input amps. I'll need to find my amp clamp. Just replaced all the boards and fets which got all the LEDs working and the lady telling me 70% load, 100% load overload if I'm hearing her correctly lol gentry sent the fets for an 8kw unit which is bigger than my mounting holes on the 5kw so I de-soldered them and put them into my 5kw mos boards if that matters.
There's nothing inside the transformer and it's cover has been removed so it's not touching.
gentry sent the fets for an 8kw unit which is bigger than my mounting holes on the 5kw so I de-soldered them and put them into my 5kw mos boards if that matters.
I'm confused here. PJ has 3 MOS board sizes...the very smallest which they only use in the 1500W inverter (I believe). And the very largest they don't use much anymore (used to be 9K / 15K). That leaves just one size MOS board--so I'm not sure what's going on here. They did change from a plate behind the FETs to simply bending the FETs to reach the heatsink...but...
It potentially could...it only takes one little solder mistake (or ruined through-hole) to cause issues. Care to provide a photo or two of the MOS boards? (Random crackling does not sound very encouraging...or safe.)
BUT...that being said, while a problem with the MOS boards could be a very solid cause for the crackling sounds, it does not explain why the inverter believes it is overloaded. I am assuming this inverter does not have an LCD?
Well my mos boards say 3kw/5kw and they ones I received say 5kw/8kw so I'm not sure.
The lcd says how many hours in use, kw used and watts output. Even in overload display say 0 watts.
I'm not home so cant send current pics.
I think what I ordered was for a power jack and what I received was for a power tank inverter.
I think what I ordered was for a power jack and what I received was for a power tank inverter.
Same difference. Power Tank is a different label on a Power Jack. Same with U-Power...except they double-rate the exact same inverter.
Guess I only have "3K v2.2" MOS boards, and then the "8K v2.2" big FET boards. Will await a photo or 2.
I have attached the pictures. Now that I pulled it out of the shed it's now saying output has problems and list all the boards I have already replaced.
Pulls .74 amps.
I ordered 5kw mos boards and recieved 8k boards but the boards in it say 3kw....
Ok, operator error. Forgot to put a board back on.
I hope you can hear the transformer making it's buzzing sound like it's trying to make max power.
The positive side mosfets are reading 1.8 volt gate to ground, the negative side is 1.1 volts. They all measure the same across all mosfets per side.
Ah, video makes a LOT more sense.
Low battery voltage alarm is probably due to voltage drop in the wires to the inverter--which are probably saving your FETs.
It sounds like the AC feedback is not working in the inverter; it's running to 200% throttle (pretty much a perfect square wave) overflowing and running 0-200% throttle again...trying to find the desired regulation voltage. I notice that the connectors on the "resistor boards" are extremely dirty. As the PJ feedback design uses an infinitesimally small signal for feedback, I wonder if cleaning these dirty spots up might restore it to functionality?
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You might also try swapping those 2 little boards. I notice the nuts on the screws are missing, have you replaced these?
The sound isn't quite "bacon frying" in my book--no snapping/crackling, just a very oversaturated 60Hz buzz. Normal operation if the feedback circuitry isn't working.
Photos showing the FET boards you received...those are the BIG FET boards used in the older 9K and 15K units. (PJ doesn't use them much anymore.) Really weird that you received those...
Yes, but I did find the FET's on the negative side were fried. Not violently failed but failed none the less. I found the FET's were the same number so I just de-soldered them and moved them over to the smaller boards.
I will try reversing those boards and cleaning up the contacts. Being in Florida humidity gets into everything if it just sits.
Assuming you've replaced the LF Driver board?
Yessir, I ordered the whole setup but never recieved the charge board, possibly it didn't come with it but I thought it did.
I was testing it on a small battery so it would drop the voltage before cooking anything.
Got it running on my main bank now, 4 agm batteries, and it runs without shutting down but something is definitely off... pictures should help explain it.
Pulling 82 amps but shows no output amperage. That usage time includes the time it was sitting in my driveway maintaining the batteries in my semi. Only pulled 4kw from it before it toasted....and that was a 1kw microwave that cooked it lol.
This is sounding a smidge more like bad FETs / blown LF driver. 82A @ no load is definitely really wrong!
Yes, but I did find the FET's on the negative side were fried. Not violently failed but failed none the less.
When was this? After the initial failure, or after replacing boards?
Initial failure. I'd be more than happy to order a whole new board assembly from power jack.com. Show to be 85 bucks for the whole setup.