MOSFET sourcing or cross reference help - Page 1
Forum section: electronics / repair

author: bCreative
author_rank: Newbie
timestamp: July 20, 2019, 01:50:31 am
content: Apologies if this is in the wrong forum. Please move it or direct me to the correct forum if need be.I need to track down at least 4 of these guys, or enough information about them to source something compatible. They're the ignition MOSFETs in my truck's ECU. Two of them are shot, two of them are marginal, and I'm competent enough with a soldering iron that it's worth a shot at replacing them before seeking a replacement ECU.They are a TO-220 package, appear to have a Motorola logo, and bear the following markings: 707 M01 R722. I can post a photo if helpful. The board in my ECU is dated 1995, so these would have probably been a high-end component back then.Thank you in advance for any help I might receive here. Either my google-fu is getting rusty, or there's really not a whole lot of info on these old components out there.

author: fzabkar
author_rank: Super Contributor
timestamp: July 20, 2019, 02:25:39 am
content: I reverse engineered the components in a Ford Bronco EEC-IV ECU dating back to the late 1980s. All the parts were FoMoCo numbered, with no hint of the original IC manufacturer's codes.Photos of the PCB may help to put your parts in context. You say that your ECU was made in 1995, but this does not seem to match any of the possible YWW (Year/Week) date codes on the MOSFET package. Normally you can at least rule out the date code and confine your search to the remaining numbers. Maybe the other ICs will give us a clue.These may not be helpful, but …https://www.hkinventory.com/p/d/707M01.htmhttps://listado.mercadolibre.com.ar/transistor-de-bobina-ecuThis supplier lists them (707M01) at US$8 each:https://articulo.mercadolibre.com.ar/MLA-611142733-707-m01-707-m01-707m01-transistor-ecu-to220-_JM?quantity=1That said, one would have to ask where these parts are sourced. If they come from China, then there is a high likelihood of counterfeits.

author: bCreative
author_rank: Newbie
timestamp: July 20, 2019, 03:31:03 am
content: Thanks for the quick reply. The truck is actually a '97, the date on the board is '95 but it is likely they used the same board over multiple years. No components on the board bear Ford badging or numbering, though the housing and covers on the ECU itself all do.Please ignore the complete crap soldering job visible in this photo. It was taken after a failed attempt at "re-wetting" the existing solder joints with a cheap iron (I was in a pinch and used what I could get quickly). I later removed and properly resoldered all 4 MOSFETs in different positions on the board as a diagnostic -- and the missing spark followed the bad MOSFETs as expected.I don't have photos of the rest of the board, and the board is currently installed in the truck. The failed MOSFETs were moved from the primary side of the dual-spark ignition system to the secondary side, to allow the truck to run while I source parts. I suppose I can pull the ECU to take photos if necessary, but I would rather not if avoidable.EDIT: Huh, not sure why the photo is upside down here... still readable tho.

author: fzabkar
author_rank: Super Contributor
timestamp: July 20, 2019, 06:50:23 am
content: FWIW, I notice that the following part was used in many ECUs (the datasheet is dated 1997):MGP20N40CL, Motorola, N-ch IGBT, internally clamped, logic level, 20A, 400V, 150W, TO-220AB:http://pdf.datasheetcatalog.com/datasheet/motorola/MGP20N40CL.pdfMaybe you could try a modern part with similar specs, or better? The drive requirements would need to be established (logic level or standard level?).See page 424:http://www.bitsavers.org/components/motorola/_dataBooks/1994_Motorola_Semiconductor_Master_Selection_Guide.pdf... and page 523:http://www.bitsavers.org/components/motorola/_dataBooks/1997_Motorola_Master_Selection_Guide.pdfEdit:What about this part?https://www.digikey.com.au/product-detail/en/on-semiconductor/FGP3040G2-F085/FGP3040G2-F085OS-ND/4963379https://www.onsemi.com/pub/Collateral/FGI3040G2_F085-D.PDF

author: bCreative
author_rank: Newbie
timestamp: July 20, 2019, 08:34:33 pm
content: Thanks for that. I'll be sure to bring my scope home from the shop Monday to check the gate level. You think they're IGBTs and not MOSFETs? That actually makes sense given the application and age.

author: fzabkar
author_rank: Super Contributor
timestamp: July 20, 2019, 09:24:48 pm
content: Most of the ignition parts at that Argentine web site were IGBTs, so that would be my guess. Motorola's databooks from that time would also suggest this. You could check the VCE(on) voltage, or VDS(on) for a MOSFET.

author: bCreative
author_rank: Newbie
timestamp: July 20, 2019, 09:57:21 pm
content: It never even crossed my mind that these would be IGBTs, though it does make sense, and I should probably stick with IGBTs in that case.Though... Would there be any advantage or disadvantage to using a MOSFET in this application if a compatible one can be found?

author: fzabkar
author_rank: Super Contributor
timestamp: July 20, 2019, 11:08:37 pm
content: I haven't looked inside an ECU in over a decade, so you're way ahead of me there. I, too, was unaware that IGBTs were used in automotive applications. As for whether an IGBT can be substituted with a MOSFET, I have no experience in this area but I would think that you would need an N-channel enhancement mode MOSFET in your case.Sorry, I can't help you.

author: bCreative
author_rank: Newbie
timestamp: July 20, 2019, 11:32:31 pm
content: Well, my searches have been awash with those, so it seems I am in lock. It also seems I wild-ass-guessed at reasonable specs, as I've been searching for parts capable of sustaining 15A or higher continuous load with 150W or higher power dissipation and at least a 15V breakdown voltage. These seemed like reasonable figures for the application and I was hoping to go as high as possible without sacrificing open/close time or gate voltage.Looks like I can start looking at IGBTs now. I'll keep you posted when I pick a viable part and attempt replacing them... or if I just replace the ECU.Thanks again!

author: fzabkar
author_rank: Super Contributor
timestamp: July 20, 2019, 11:48:48 pm
content: FWIW, IGBTs are used in inverter microwave ovens and induction cookers. They are typically rated for 1000V and 30A - 60A.https://www.infineon.com/dgdl/Infineon-IHW30N110R3-DS-v02_01-EN.pdf?fileId=db3a304327b897500127b963455e0089https://www.promelec.ru/pdf/GT60N321.pdf

author: bCreative
author_rank: Newbie
timestamp: July 21, 2019, 02:12:34 pm
content: Well, I found a viable part. Doesn't matter, though. When I pulled the ECU again to confirm a few things, I took some measurements, and it turns out I flubbed it up pretty bad when I was resoldering some pins on the connector, which is what was causing all holy hell to break loose when I plugged in both sets of coils, as well as the occasional misfire. Since the errant solder blob is between the board and a 108 pin connector, the remedy is a new ECU as there is absolutely no way I am desoldering that entire connector to clear it.I removed the IGBTs (yes, it turns out that is what they are) that drive the (not plugged in anyway) secondary coils as a temporary measure and the truck is drivable in the interim.Full details below, if you care to read them. If not, well, thank you for stepping in to help, and I'm sorry to report that this endeavor turned out to be a complete waste of time, aside from the now solid diagnosis of an issue I've been chasing for some time.My truck, a '97 Ford Ranger, has a dual-spark/wasted-spark ignition system. The theory of operation is such that there are two spark plugs (primary and secondary) on each cylinder and cylinders are split into pairs, sharing a single coil, for the purpose of spark control. Cylinders 1 and 4 are one pair, with 2 and 3 making the other; this is the wasted spark portion of the system, so named because both cylinders in a pair will have spark at the same time, though one will be on its exhaust stroke, thus wasting its spark. The primary ignition circuit operates at all times, the secondary only under load or after the engine reaches operating temperature; this is the dual spark portion of the system.Due to how the dual spark system works on this engine, the engine can run on the primary coils alone, but not so on the secondary coils, as they do not activate during a cold start. This was the cause of my initial problem: a failing IGBT on the primary ignition circuit was causing rough idle, missing at idle, and occasional (becoming more frequent) stalling when returning to idle, until the engine warmed up. No misfire condition was present under load or once the engine reached operating temperature -- both conditions under which the secondary ignition circuit became active.My initial proof of this fault was to drive the vehicle until the engine reached operating temperature, then disable the primary ignition circuit by disconnecting the input from the coils. I noted no change in engine operation, which is what I expected as the engine was at operating temperature and the secondary coils were functioning. I, then, further proved the fault be reconnecting the primary ignition coils and disabling the secondary ignition coils. My rough idle and misfires returned, and the misfire condition worsened under load.The fault was clear, something in the primary ignition circuit was not right. I was working with new (and OEM) coils, plugs, and wires, but did not automatically assume them to be good. I swapped coil packs from primary to secondary and repeated my test with identical results -- my coils are good. The misfires were being reported primarily on cylinder 1, with most of the rest on cylinder 4, so I focused my efforts there. The spark plug wires for cylinders 1 and 2 are close enough in length that I was able to swap them, along with the spark plugs, to see if the issue followed. It did not, confirming that my spark plugs and wires were good. If the issue were on cylinder 4, it would bear the majority of the misfires.That left the ECU.There was no obvious or apparent damage and the combination of a thick conformal coating and lack of microscope meant inspecting solder joints was a no-go. So, I set right in on scraping the conformal coating off around the IGBTs and the related pins on the 108 pin connector, re-wetting the joints with some fresh solder, and wicking them clean before applying new solder. That's when the photo I posted earlier was taken -- and I did not reinstall and power up the ECU in that state. Instead, I removed the IGBTs, wicked their leads and the board clean, and reinstalled them in the same order in which they had been removed. I repeated the above testing with identical results. I was then ready to condemn the IGBTs themselves.That's when I removed them again, and reinstalled them in revers order (e.g. if you label them A B C D, I reinstalled them D C B A). At this time, I also noted that one of the pins I resoldered didn't look too great, so I touched it up. *THIS* is where I screwed the pooch.With this newest "repair" (this was purely diagnostic at this point) attempt, the observed behavior was as follows:- With both ignition circuits active, I experienced rough idle and frequent hard stalls (the engine completely locking up, resisting the rolling inertia of the truck and locking up the wheels) at low speeds when taking off from a stop.- With the secondary ignition circuit active and the engine warmed up, I experienced similar (but slightly worse -- we'll get to why in a moment) behavior as was previously seen with just the primary ignition circuit active.- With the primary ignition circuit active, I experienced much improved idle, but frequent misfires under load.And last night, when I took those measurements, I realized why: I had created a short between the primary 2-3 and secondary 1-4 circuits. With both sides enabled, every time cylinder 2 and 3 had spark on the primary side, 1 and 4 had spark on the secondary side; when spark was called for on 1 and 4 on the secondary side, and that IGBT decided to function, 2 and 3 would also see spark on the primary side, causing the hard stalls. With just the secondary side enabled, the issue should be obvious to anyone following along: the IGBTs on that side are damaged, coupled with the cylinders 1 and 4 always having spark due to the short to the primary side. Likewise, with just the primary side active, cylinders 2 and 3 were getting spark mid-stroke whenever the secondary IGBT for 1 and 4 decided to work.Seeing that I had no viable way of clearing the short (which would have allowed me to enable both ignition circuits again) I chose to render it harmless and removed the IGBTs for the secondary ignition circuit. The secondary coils remain unplugged, but the truck runs and drives more or less fine. It is clear under certain load conditions that the IGBTs which remain are failing, but it will get me to work and back until I can replace the ECU.Thanks again, if you stuck with me through that novel, which I totally expect you did not.

author: fzabkar
author_rank: Super Contributor
timestamp: July 21, 2019, 08:36:15 pm
content: That's some clever troubleshooting. Thanks for the explanation. Hopefully your experience will benefit someone.BTW, I revisited my EEC-IV notes and it turns out that all the FoMoCo IC numbers begin with 7. That could be a red herring, though, since the FoMoCo transistor numbers begin with 5.

author: amyk
author_rank: Super Contributor
timestamp: July 22, 2019, 12:06:08 pm
content: Dual spark plugs? That's not something common in an automotive application... but is normal in aviation engines.My suggestion for clearing the short is to use a carefully-placed drill bit.