Looking for a better quality Mosfet

[daves66nova]

I had the hood of my car kinda open when it rained. It's a '66 Nova. The Crane Cams HI-6 ignition box got a little wet. I didn't know about this til I tried to start the car and it wouldn't start. I took it apart and put power to it and heard this humming sound. I then touched different parts of the board and felt 2 slightly hot pieces that I looked up and found out are "Mosfets"? The part no.s are RFP70N06 and IRGBC40S. Mouser has RFP70N06 at 1.60 and IRGBC40S seems to be obsolete. Is there anything that supersedes IRGBC40S? Mouser and Digikey don't have it How about some high quality brands of these?. Would these pieces make the humming noise? Thanks.

 

[LotI]

Metal oxide semiconductor field effect transistor...I haven't said those words in decades!

 

[Linctex]

Send it back to Crane for repair.

The MOSFETS themselves aren't bad if they are handling an excessive load - like they are being told to do by a bad circuit board inside!

 

[Papa Bear]

Originally Posted by Linctex
The MOSFETS themselves aren't bad if they are handling an excessive load - like they are being told to do by a bad circuit board inside!


True

 

[Cujet]

MOSFETS are prone to failure under certain circumstances. Many of the older ones were utterly intolerant of even the most minor of overloads, over voltages, or temperature swings. Furthermore, older ones often have a limited lifespan. As mentioned above, the drive circuitry may be (and most likely is) the problem, but don't discount MOSFET failure either. In many cases, such as aircraft autopilot drive circuitry, the MOSFET is first place I look.

https://www.powerelectronictips.com/how-and-when-mosfets-blow-up/

You should have no trouble finding something equivalent if you want to replace them.

https://alltransistors.com/igbt/crs...V&ic=50A&tj=175&caps=TO220AB

 

[Virtus_Probi]

The IR part (International Rectifier, now Infineon which used to be Siemens) is an IGBT, Insulated Gate Bipolar Transistor which is a power bipolar triggered by a MOSFET...all the power is handled by the BJT (Bipolar Junction Transistor).
There is a place called AERI that claims it sells them, but don't be surprised if it's actually a clone and I don't know if they deal with selling small quantities.

I'd try cleaning whatever you can reach off with some alcohol before you try to hunt down obsolete parts!

 

[OldSparks]

I looked at the datasheet for the IRGBC40S - that's an 'insulated gate bi-polar transistor'. Mouser has a variety of possibilities. Perhaps someone with a power control background could help with an appropriate substitute.

 

[MolaKule]

Possibly a shorted coil?

https://static.summitracing.com/global/images/instructions/crn-6000-6400.pdf

 

[CT8]

Mosfets were the big whoop for the electric forklift control before I quit the business.

 

[Virtus_Probi]

Humming is a pretty general symptom, when I was working on a power supply ages ago and it hummed the issue was excessive ringing on switching edges and I had to add a snubber (RC) to fix it...the bad news was it sucked power.
Humming could also be a control circuit oscillating wildly...again, I'd try cleaning off whatever got wet before replacing components, even when rainwater dries off it can leave conductive paths you don't want behind.

 

[meep]

they don't like kickback. The terminology escapes me but aren't diodes & caps used across the output to bleed off unwanted kickback from inductance? If you're gonna swap the 'fet, I'd examine those as well.

 

[Virtus_Probi]

Originally Posted by CT8
Mosfets were the big whoop for the electric forklift control before I quit the business.

We would not have reasonably priced home PCs, cell phones, and lots of other things without MOSFETs...it's no fun designing a microprocessor or anything like that in bipolar technology.

 

[Virtus_Probi]

Originally Posted by LotI
Metal oxide semiconductor field effect transistor...I haven't said those words in decades!

The funny thing is that metal gate FETs are really a niche technology, polysilicon gates have been standard for many years.
If you have a true MOSFET these days, it is usually a parasitic device in a high voltage design that is letting two or more devices "talk" when they should really be isolated...
For whatever reason, the term MOSFET stuck and maybe it just sounds better than POSFET?

 

[daves66nova]

Originally Posted by OldSparks
Perhaps someone with a power control background could help with an appropriate substitute.

I'd REALLY appreciate it. They do have a slight burnt carbon smell to them. since I'm replacing them, i might as well put in something more modern,better quality,etc.

 

[Virtus_Probi]

Looks like the IKP30N65F5 could be a reasonable modern replacement.
It has an integral diode to keep the C from being pulled way below the E and is probably faster than the original component...these would normally be "good" things, but could also easily cause problems in your application.
Putting a faster component in a circuit designed around a slow one could easily lead to an oscillation problem, for example.
A friend of mine used to work in finding replacements for obsolete components in military applications (think about a Standard missile that was designed 25 years ago and needs to be repaired, for example) and he said it was really a hellish problem.

Good luck!

 

[daves66nova]

This is what Digikey recommended, IGP40N65H5XKSA1. Are they supposed to get really hot? I applied power to the ignition box for about 8 seconds and only 1 mosfet got really hot, to the point it smoked a little. Of the other 2, while different, 1 was cold, other bigger one was skin warm.