transistor ID help

Jjona5

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So I'm working on an amplifier and I have four of these on the the input side

It looks just like this

MT A5
ONO5HD
J823 (then the motorola symbol)

Standard three leg looking unit but I can't find it online. I'm sure some of you seasoned repair guys will know exactly what this is and where I can find it. Sorry about the picture it was the best I could do...guess I should buy a good sized magnifying lens.

 
You are correct MTA50N05HD by Motorola Power MOSFET

M = Motorola
T = TMOS
A = TO220 ISOLATED Package
50 = 50 amps
N = N Channel
05 = 50 Volts
HD = HIGH CELL DENSITY
 
So you guys are pretty sure about that? I appreciate it. I'll go ahead and order them then. Wonder if radioshack has them? I'll check in the AM.

Thanks again,
Jonathan
 
There is usually no problem with going higher in the VDS voltage. For real picky applications, this can sometimes result in a higher RDS(on) resistance. In your case, you are only going up by 10 volts so this shouldn't matter.

The one thing that is questionable is the VGS(th) rating. This is the gate threshold voltage -- voltage in which the part is turned on or off. The part you linked to has a VGSth = 2-4 volt range. Can't compare to the original as I can't find datasheet to the original.

Also, the original had an insulated tab. The one in your link has a non-insulated tab. You will need to use a mica insulator PLUS a screw isolation such as 7721-7PPS. The 7721-7PPS is a shoulder washer used to separate the screw from the metal tab...or just use a nylon screw.
 
The TO220 ISOLATED Package is not the same as standard TO-220
If you use a standard TO-220 package type such as MTP50N05 which is
the same transistor just in standard TO-220 package
you will need to isolate it from the heat sink use a plastic screw with mica sheet under
transistor

Also MTP50N05 crosses to an NTE Equivalent NTE2395 N channel MOSFET but needs to
be isolated also.
 
Will the heat dissipate properly if I insulate it like that though? I really appreciate all of your help btw.
 
Well I already use the grease but I figured if I insulated it with plastic it wouldn't really transfer the heat very well.
 
Last edited:
Non-isolated transistor --- definitely use mica insulator with thermal compound (both sides of mica). *OR* also use a heatsink gasket such as a Berquist SP900S-0.009-AC-54. This is a thermal phase changing insulator with built in fiberglass electrical insulator. When heated, the insulator 'melts' a bit (just becomes soft) and becomes highly thermally conductive. Re-hardens as device cools. Has a fiberglass layer such that it remains electrically insulated so no mica insulator is required.

AND don't forget you need to insulate the mounting screws as well. If using a metal screw, use the plastic shoulder washer (7721-7PPS) specifically designed for this type of use. Else use a nylon screw. This would be the only place that plastic would be used.
 
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