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Old 19th December 2005, 03:46 PM   #1
chlim74 is offline chlim74  Singapore
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Default Power MOSFET

Hi all,

Just came across this forum.. U guys here seems real knowledgeable..

Need some serious help.. Me reside in Singapore (Asia)

Got a Sony XM-D1000P5 Monoblock..
Dunno why it just died and blown my 60A fuse at my fuse box.

Send to Sony and found that the MOSFET SSP45N20A needs replacement. They quoted me damn ex, and say no stock, need to wait, dunno how long..

Search around, can't find the part, and realise later that it's an obseleted part.

Is there any other more common part that is more readily available that can do the same task?? While i try to look for IRFB42N20D as recommended in one of the threads.

Many thanks...
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Old 7th January 2006, 01:03 PM   #2
Clipped is offline Clipped  Thailand
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hey i have a few transistors laying around that may help you out, free of charge just give me your address and i'll send them to you: if they are compatible:


im to lazy to do a datasheet search for you so if you find one thatll work let me know


ps..im in thailand so it shouldnt take too long to get to you
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Old 7th January 2006, 02:32 PM   #3
Eva is offline Eva  Spain
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This device is not usual at all, it's obviously not he classic switching device from a 12V push-pull PSU.

SSP45N20A, V(dss): 200V; 35A; 0.065 Ohm; advanced power MOSFET in 3-pin TO-220 (typical input capacitance appears to be 3.3nF)

It appears that Fairchild replaced the original SSP45N20 by SSP45N20A and then by SSP45N20B. You may still find the B version for sale, altough it's also obsolete now. How this can happen? Because car-audio manufacturers usually buy lots of long-ago obsolete parts at very good prices and build their amplifiers around them. (The worst case happens when a long-ago discontinued exotic IC has to be replaced).

The closest device in the current Fairchild catalog appears to be FDP39N20, and FQP34N20 may be also suitable. Note that both devices feature lower input capacitances (and gate charges) so the value of the gate resistor may be increased proportionally (theoretically).

Also, you may try to find similar devices from other manufacturers.
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Old 18th January 2006, 03:37 PM   #4
chlim74 is offline chlim74  Singapore
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Hi guys,

Thanks for your help and offer..

I managed to get IRFB42N20D.
Will let you know if i need your transistor cos mine doesn't work.

Here's what happen.. Replaced all 8 SSP45N20A by IRFB42N20D.
Initial problem of 60A fuse blow upon power on is resolved.
But... the amp goes into protection mode when i turn up the volume( Not very loud, just moderate)..

Now headache.. Dun know what's wrong..
Looks like i got to give up on the amp??
Is there possibility that the replacement transistor is not compatible resulting in this problem??

Thank again.. Really appreciate..
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Old 18th January 2006, 04:12 PM   #5
Perry Babin is offline Perry Babin  United States
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Are the output caps (four 220uf/160v electrolytic caps near the speaker terminals) getting hot?

I had an amp that was doing the same thing (going into protect at high volume). I suspected the output inductor. I never had a chance to check it because the customer decided to pick it up before I received the service manual. If you want to pull it and have someone check it. It's supposed to be 230uH.

As a side note...
I used the same replacements as you but didn't want to recommend them because I hadn't successfully repaired the amp. I think they were a good replacement because the amp didn't pull excessive current at idle.
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Old 23rd January 2006, 05:16 PM   #6
RDCXBG is offline RDCXBG  United States
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B&D Enterprises www.bdent.com has the SSP45N20A, pretty steep too $13.55 a pop.

I have an older MTX Thnder 8302 here that uses them in the amplifier section. It has a couple shot ones in it and then 6 of them still good. Still debating whether or not to cough up that much to repair an amp I'll probably never even use.
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Old 24th January 2006, 07:04 PM   #7
swordfish689 is offline swordfish689  Canada
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If you get a newer 8302, the ones with surface mount resistors, they use irfb45n20d. Also all the mtx amps like 6500d or 4250d were upgraded to that transistor. I seen that digikey sells them. I think it was 2 to three dollars. Also that is excellent replacement tranisitor. Make sure you mearsured the resistors near the transistors that you replaced, they're known to blow or change value when under stress i think there 47 ohm.
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Old 24th January 2006, 07:15 PM   #8
sdman is offline sdman
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Does anybody have a schematic or service data on the 8302?


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Old 25th January 2006, 11:18 PM   #9
swordfish689 is offline swordfish689  Canada
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Sorry, no i don't have them. If you give me some information i can help you out. I have fixed a few.
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Old 28th January 2006, 03:19 AM   #10
Perry Babin is offline Perry Babin  United States
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Hi chlim74,

I recently had an MTX 6500d that was showed the same symptoms as your Sony (and the Sony that I worked on). It had SSP45N20As in it. I tried the IRFB42N20Ds and they allowed the amp to play at low to moderate volume but at high volume the amp would distort badly and shut down. After finding no other faults, I decided to try different transistors. When I used IRF3415s in it, it played fine. Although the 3415s are not suitable for your amp (too much rail voltage), you may want to try a different transistor. There may be nothing else wrong with your amp.

If you get the amp working, post the details of the repair.
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