Where to buy Mosfet ???

Photowhit
Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
So I have a new charge controller in and I want to try to swap out the shorted/destroyed Mosfet rectifier(?) I've been calling it a voltage regulator but I guess it's really a Mosfet.

So I look around and up pops Ebay, the Mosfet is a IRF2807, it appears the other numbers represent lot numbers? or dates? I want to use high quality Mosfets so where do I look where quality not price is the driving factor?

When I soder these in should I use silver soder? I think it has a higher melting point, or will the basic flux core soder be fine?

Any ideas will be helpful.

Thanks in advance, -Whit
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.

Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Where to buy Mosfet ???

    you are correct in that it's a mosfet,
    http://www.irf.com/product-info/datasheets/data/irf2807.pdf
    i'm not sure what other numbers you are referring to, but they have no need to date transistors of any type that i know of. do a search on mosfets or go to digikey to purchase and no other company will make that mosfet technically as another company with a similar item will most likely have different letters and numbers to designate it. doing this is called substitution and the substitution may not be an exact match. i doubt they are very expensive, but look around as to who has a good price on that mosfet for if it is an irf2807 they are identical and from the same company.
    i don't know if they require the special so called silver solders or not. if not then i'd opt for the kind of solder that has the real silver in it and not the nicknamed stuff because it appears shinier and it has no silver in it.
    http://www.radioshack.com/product/index.jsp?productId=2062725
    hope this helps.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Where to buy Mosfet ???

    Thanks neil,

    The other numbers on them were 944g and 945g, hence I figured a batch number after finding a spec sheat for the IRF2807.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: Where to buy Mosfet ???

    Iwould not recommend you use silver solder unless you experienced with it as it melts at a higher temp and if you dont have a temp controlled solder station and know how to set it correctly you can easily overheat the component or not make good solder joint.. resin cored solder will work just fine. about .8mm size is best.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Where to buy Mosfet ???

    i should add that the silver bearing solder is not the same stuff as silver solder and is better than regular rosin core solder. the term 'silver solder' is a misnomer probably concocted by some plumbers thinking it looks like silver to them. they were referring to the higher melting point solder with a different lead/tin ratio. silver bearing solder is different and has a good melting point with a slightly lower resistance because the real silver in it is a much better conductor.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: Where to buy Mosfet ???

    The silver solder Iwas referring to is the "stuff" that does have real silver in it and is mostly used for electronics work. I use it every day at work. but it has a higher melting point and if not experienced you can easily overheat the part being soldered usually because the tip is not hot enough or not heat the solder enough so it flows well. For most home workers good old resin cored lead tin works just fine.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Where to buy Mosfet ???

    My concern was just in the heat generated and a higher melting point.

    I have used it before, but it's been a while, I have a 100 watt thin point iron I bought just to use with the silver bearing soder. I really didn't notice a big difference, maybe a little 'stickier' I don't have a temp control iron, I have a cheapy 30 watt that I use for most things.

    I don't have a desodering tool just a bulb and an iron, so a mistake might be difficult to correct, but I've gotten better over the years.

    Just wondering if the higher melting point might be required, as the Mofset is backed to a cooling fin. As to the cooling fin, it appears to have a thermal tape between it and the Mofset, I wonder if it will be fine to reuse or if I should scrape it off and apply thermal paste?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: Where to buy Mosfet ???

    If any one interested in usless trivia where I work a test was done where 100 pieces of 4" long copper wire (if I remember correct about #12) the thens were placed parallel to each other by about 1" (not twisted together) then one lot were soldered with lead tin another lot with lead free tin antimonyand a third lot with silver solder(with real silver) 48 v was applied and the wire connected to a 1a load. ok 100 pieces of wire in series only soldered together.
    the difference on a top of the range Fluke multimeter was no difference in the volts at the load. it took a $2000 lab desk volt meter to find differences of about .001mv between each one. thats 1/1000 of a mv between ordinary solder and tin /antimony and another 1/1000 between it and the silver solder. not a lot to worry about.. the other test that was done was to put each type of soldered joint in salt water to test for corossion resistance . The test was done for 48 hrs the results. all were useless.
    Bring on the next type of wonder solder please.


    Just wondering if the higher melting point might be required, as the Mofset is backed to a cooling finThe transistor will be long dead before the solder melts
  • Slappy
    Slappy Solar Expert Posts: 251 ✭✭✭✭✭✭
    Re: Where to buy Mosfet ???

    ""I don't have a desodering tool just a bulb and an iron, so a mistake might be difficult to correct, but I've gotten better over the years.""

    Try desoldering braid, it works very well, I picked some up a couple weeks a go, first time using it, and it does wonders, it even cleans the solder out of the circuit holes.

    http://www.radioshack.com/search/index.jsp?kwCatId=&kw=desoldering%20braid&origkw=desoldering%20braid&sr=1
  • lorelec
    lorelec Solar Expert Posts: 200 ✭✭
    Re: Where to buy Mosfet ???

    IRF2807 -- Digi-Key has the genuine IR part for $2.39 (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRF2807ZPBF-ND). No minimum order, and you can specify First Class Mail when you order something like this (not too many other vendors will do it) for the cheapest shipping.

    Jameco also has a "various manufacturer" IRF2807 for $0.69 each, but shipping will be UPS Ground or Priority Mail, so D-K is probably your better option.

    Use regular old 60/40 rosin core solder. 100w soldering iron is pretty big...be careful with the heat. The only reason you'd probably want to use a silver alloy is for lead-free work. The antimony stuff is terrible to work with (although at 100w you might have a chance!). The "SAC305" alloy is pretty good (3% silver, 0.5% copper, rest tin) if you want to go lead-free.

    You can probably reuse the insulator as long as it's not damaged. The FET might require isolation from the heatsink, so put the new one in with the same hardware (or equivilant) that the old one came out with.

    I might also suggest that you determine why the FET failed (if you haven't already) before you replace it with another one ... and wouldn't hurt to order at least two of them.

    Marc
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Where to buy Mosfet ???

    just to clarify, photowhit asked about silver solder and that particular solder i don't advise using it. if you must go lead free lorelec gave you an option with the SAC305, otherwise the standard rosin core or silver bearing solders can be used.
    try using the 30w iron and then if that doesn't do it go with the 100w carefully.
    go with the original mosfet unless you know the other manufacturer's brands would work. they may seem identical to the original, but may have poorer voltage abilities or thermal characteristics for example and some may be identical or better too. some chinese made mosfets also have reared their heads to be inferior even though speced as good.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Where to buy Mosfet ???
    lorelec wrote: »
    IRF2807 -- Digi-Key has the genuine IR part for $2.39

    I might also suggest that you determine why the FET failed ...

    It appears tp have been shorted by a lady bug(not the real ones the imports - lol.

    The other might have failed from increased pressure after the first.

    The 'thermal tape' stuff is all thats holding them to the fins, ie; no screws, is there typically a need for electrical insulation from the fin? I haven't removed the old mofsets yet but the first one is a mess cracked and crumbly.

    I think I'll go ahead and order 3 of the originals from your link, someone suggested they would all be made by the same manufacturer so I just picked up 4 off Ebay, but I'd rather have the original replacement.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Where to buy Mosfet ???

    generally, if the thermal tape is used, it's needed for electrical isolation. otherwise, it's less expensive to just put a dab-of-grease on the part and be done with it.

    Something has to hold the part to the heatsink, either a spring clip, screw & nut or something. To only have the insulator pad adhesive be the only force holding the fet/heatsink together is unusual.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Where to buy Mosfet ???

    Also, check the drive circuits for the MFET too... It is possible that the short may have taken out something in the low power control path too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Where to buy Mosfet ???

    +1, close to 100% of the time, a failed Mosfet shorts the gate pin to drain pin and poof goes the drive circuits. Replacing the just the Mosfet will just blow up the new parts
  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    Re: Where to buy Mosfet ???

    I find that normally when a FET blows, the whole FET turns into slag and all 3 pins are shorted. Very rarely do I find that the driver has been hurt.

    That statistic may, of course, depend on the design somewhat.

    Once in a great while though the driver will get hurt so is worth checking out. When the driver does go bad, replacing the gate drive resistor as well is a good idea.

    boB
  • lorelec
    lorelec Solar Expert Posts: 200 ✭✭
    Re: Where to buy Mosfet ???

    There are self-adhesive sil-pads, which you can also get through Digi-Key, but normally they're single sided (adhesive to secure the pad to the heatsink, not to the FET). Securing the FET with one of these alone wouldn't be my preferred choice, but if that's what they did... You usually want some kind of isolation from the heatsink, if for no other reason than to help prevent it from becoming an antenna.

    If you're lucky, the FET has a gate resistor (the gate on power FETs is almost always pin 1, looking at the FET from the top). If it's there, it'll be low value, on the order of 10 ohms or so. These usually burn up during a short and will often protect the drive circuitry.

    Marc
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Where to buy Mosfet ???

    I guess I should have said that there are spring clips that press the Mosfet into the tape (with a plastic spacer) I'm just use to voltage regulators screwed into small fins.

    OK, I'm not well educated on the the "check the drive circuits" or "low voltage circuits" How would on go about testing? I could test the resistence for the float and bulk?

    Any chance I could get one of you guys to look at the mosfet specs and see if I might be wasting my time?

    Would this be the"gate" "Static Drain-to-Source On-Resistance .013 Ohms"?

    Here's the worst of the damage, the lady bugs were under the wires going to 3 of the mosfets you can see some discoloration on the one above;
    mosfet.jpg?t=1269295655
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • lorelec
    lorelec Solar Expert Posts: 200 ✭✭
    Re: Where to buy Mosfet ???

    Looks like you have other FETs in parallel with Q7. R17-R21 (and probably R12-R16? -- above the top of the photo) would be their gate resistors. If it was me, I'd remove Q7, check the other FETs for shorts (make sure they're ALL OK) -- and if they are, you could probably power up the controller just fine for testing without Q7 in place. You'd have to use a scope to check the drive signal's integrity, but I guess if the controller powers up and functions OK, the drive is probably good. There's still a chance that the driver might have been compromised some, and that it could fail prematurely at some point in the future. If all is a go at this point, replace Q7 (check its gate resistor, too). It looks like those FETs might not be in the metal tab TO-220 case? Are they fully encapsulated in plastic? I might just not be seeing the photo right. And what about Q6 -- how does it test? Also, what kind of controller is this?

    Marc
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Where to buy Mosfet ???

    They just have a plastic 'cap' that the spring sits on.

    This is the 60 amp PWM charge controler out of the Pulse Energy / Trace PC250 Power Center.

    I left this running after, after the magic smoke escaped, it would not hold bulk charging current when exposed to full sun, ie the voltage just continued to climb (we had little full sun and I disconnected it when it reached 31 volts or so, this was an observed turning on of the controller and watching the voltage climb to 31+ within 5 minutes)

    After dusk the 10 segment voltage level seemed to be working. I could leave the controler running and it wouldn't reach bulk on the heavy overcast days.

    I've since replaced it with the controller out of a Trace TC60 same board with a different configuration. As it turns out the TC60 appears to have been used for a diversion load as the bulk is set for 28.1 volts, I haven't had it up and running (with me there) to see what the float is set at. I'll reset these after I've seen it fall back to float, I'd like to see if the voltage is correct for the current setting before changing it.

    I haven't tested the other Mosfets, nor do I have a good feeling of how to go about it.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Where to buy Mosfet ???

    if you go to replace the resistor, now that may require more skill than that of the mosfet as those are surface mount components. low wattage irons are advised here in addition to good eyes.
  • lorelec
    lorelec Solar Expert Posts: 200 ✭✭
    Re: Where to buy Mosfet ???

    You can test the FETs with a multimeter and "diode check" mode if you have one. Gate (pin 1) to drain (2) or source (3) should read infinite. Source to drain should read infinite one way and ~0.5 the other way. Sometimes a meter will trigger the FET into conduction, so you might get some other weird readings, but gate to any other terminal should read infinite resistance, otherwise you probably have a short. All of these checks are done without anything else connected to the controller.

    Marc