Continuing AIMS Inverter Diagnostics, Transistor Testing

[@beforebefore]

if someone else hasn't already mentioned it... cut transistor leads just above the PC board surface first, then removing the lead stubs one at a time is very easy, then use the solder wick to clean the holes. Always check every one of the MOSFETs like was shown... you did good in that. Also never replace individual MOSFET transistors when you have a group connected in parallel like these are... the remaining "good" ones also went through the same thing that destroyed the dead ones... replace FULL parallel sets so you KNOW they are all good. (transistors can indeed be "partly damaged", and fail later)

[@LithiumSolar]

Thanks! I ended up just buying a new MOSFET board. I do still have the old one though, maybe I'll dig it out and try repairing again some time.

[@stephenvasquez7853]

Thank you for this video. Having the same Inverter, and a lot less knowledge about this than you do. I’m glad I have this to reference in case the same thing happens to mine. So thank you! Can’t wait to see it back in action. Good luck!

[@diydan6045]

Good job

[@HBPowerwall]

Great vid, I learnt something new :)

[@bjtaudio]

Also will need to verify the drivers are not damaged too.. re power it up but limit the current to a few amps, and verify the mosfets are switching correctly.

[@station240]

If none of the mosfets (they aren't transistors) are shorted to gate, then it should be ok. The main concern is if the gate voltage is stuck high, or low, then the mosfets would be destroyed again.

[@LithiumSolar]

Please forgive my lack of electrical terminology, but doesn't the FET part of MOSFET stand for Field Effect TRANSISTOR?

[@LithiumSolar]

Either way, you are correct. I think one side is stuck... I ended up replacing both the MOSFET board and control board.

[@AveRage_Joe]

Nice Find! Hope the new ones fixes it all up!!!👍

[@atta30]

A really cheap and so much better way to desolder if you are using that cheap solder wick is to put some at least decent flux on the desolder wick I use a flux pen it makes it desolder 10x easier and two pens you can get for $10 and they will last you a long time

[@LithiumSolar]

It's the rubberized conformal coating making it difficult to cleanly unsolder. The wick is not a cheap brand, just very old.

[@frankz1125]

On my high freq. inverter there was a small circuit board the company sent as well as the mosfets when mine blew. Dont know if it is the same with low freq inverter. Talk to Aims. Good luck

[@LithiumSolar]

Yep - same thing. MOSFET board and control board.

[@rays.2480]

In my experience with car amps and high power inverters. if one of them mosfets are bad, the highly likely hood, all the others will have some damage.. i never have had one yet that had just a few bad..some will short, others will be weakened. it is best to change all of them...and when you order them, make sure they are a MATCHED SET..if they are not properly matched, you might have the same issue again.. Beware, adding larger caps, will be more of a surge when connecting the battery... use a resistive load to slowly charge the caps up...then connect the battery cables..

[@rcinfla9017]

You are dealing with battery H-bridge MOSFET's. Looks like eight in parallel for each of four H-bridge sides. Long heatsink are all the positive battery side MOSFET drains. Two separate heat sinks on the other side are low side H-bridge MOSFETs. You pulled the highside and lowside MOSFET's on half of the H-bridge. Whenever you have blown out MOSFET's you should not only check the series gate resistors but also the gate drivers, particularly the high side MOSFET drivers since they are typically opto-isolated drivers with only about 12-15v floating supplies which are vulnerable to overvoltage blowout when MOSFET's get shorted, with gate to drain shorts. Low side drivers are often discretes as they have a ground reference of negative battery supply.

[@mrfrog8502]

In the future first check the resistance between gate and source on each. There should be couple of kilohms but not a short. That way you can find one which one is likely shorted without desoldering all of them.

[@bostjantrancar9605]

The same transistors..... Caps are 6800uf.....on the next maintenance I will change them for 10000uF 125v gold caps to better filter ripple on dc side......

[@james10739]

Ya i have never had much luck with solder wick and the sucker works but you melt the tip so i bought a cheap desoldering iron from ebay it is basically one of those solder sucker just with an iron at the tip

[@BastelPichi]

ive you repair a inverter again, then first resolder all not blown mosfets and than make a test with a very small load.

[@mark_osborne]

What did they charge for the MOSFET board, if you don't mind ?

[@LithiumSolar]

Both boards (Control + MOSFET) were $450. It's been a while, but I think the MOSFET itself was $300. Their support was very friendly - if you need to order parts, they'll get you a quote.

[@mark_osborne]

@@LithiumSolar thanks for the reply !

[@sporktar]

Informative video. If this fix doesn't work, can you buy a replacement board from AIMS?

[@LithiumSolar]

Yes, that's what I ended up doing. I'll have an update soon. They are actually out for delivery today.

[@sporktar]

Awesome! Good to know their support is responsive, I've had my eye on an AIMS inverter for a while

[@LithiumSolar]

Sorry for not following up sooner. I have been busy with life and haven't had time to make videos recently. I installed the replacement parts from AIMS and the inverter has been working fine since. I'll try to post a follow-up but it might be another week or two.

[@danielburress6288]

You can I did and it blew as soon as I switched it on 727 dollars gone

[@gckuisch]

​​@@danielburress6288 what did you blew? The new boards or did you replaced the mosfets on the old board?

[@gtj2020]

Hey brother, hoping you could advise where to buy a NTC thermistor like one screwed on heatsink in your video. Been searching everywhere and ?

[@LithiumSolar]

They're a common part, just search for "10K Thermistor"

[@danielburress6288]

Hey did you ever find out what’s wrong I paid 727 dollars to aims for a new pcb it blew as soon as I turned it on I’m wondering what was wrong with yours ?

[@LithiumSolar]

I never figured out what specifically was wrong. I replaced both the MOSFET board and the control circuit board. I think the original cause was a wire shorted into the DC busbar, but as for the specific component that blew... No idea.

[@stevenaubin3362]

Is it fixed ? Does it work ?

[@LithiumSolar]

Yeah I ended up ordering a new board from AIMS and just replaced the whole thing. It's been working GREAT since.

[@stevenaubin3362]

How long have you been running it and how much draw normally if you don't mind I'm looking at inverters and all input is greatly appreciated. Thanks again.