Peavey SJ6357 substitution

[Axtman]

I cannot find a data sheet for the Peavey SJ6357 NPN output transistor. Can I replace the SJ6357 with a MJ15022 NPN output transitor?

[The Dude]

peavey cross reference.pdf

[Jazz P Bass]

Peavey themselves would cross the SJ6357 to the MJ15003. (NPN 140V output TO3)

Will the MJ15022 work?
Probably.

I would not mix them with existing SJ6357's.

PV Semi Cross Ref 2009[1].pdf

[Axtman]

Thanks The Dude. I have a bunch of MJ15022 transistors lying around that I wondering if I could use them up.

[Axtman]

I was planning on installing 4 (of 8) on one side. One output transistor and the other three gave me funky measurements. So all of them get replaced!

[The Dude]

Jazz P Bass hints at it in his post. It's a good idea to keep output transistors at least somewhat closely matched/the same type so that some or 1 is not drawing substantially more or less current than the others. They are all paralleled, so you want them all doing approximately the same thing. For that reason the 15003 would be a better choice. There are those that recommend replacing them all because they can vary substantially from batch to batch. In a perfect world, maybe yes. IMO, replacing the shorted ones with exact replacement is close enough. Beyond that, you add expense to the repair that most won't tolerate.
Will a 15022 or 15024 work? Yes, in a pinch. Have I done it in a pinch? Yes. Is it recommended? No.

[Axtman]

Is this price too good to be true?

MJ15003 - MULTICOMP - Bipolar (BJT) Single Transistor, General Purpose, NPN, 140 V, 2 MHz, 250 W, 20 A, 25 hFE | Newark element14

[J M Fahey]

Donīt shop for price, get the real one at Mouser and pay the extra buck.

[Enzo]

That is dirt cheap for those, but I do trust Newark as a seller. I never screw around with my power semis, I buy real Motos (On Semi) from Mouser.

Remember your transistors are in parallel on the board, and of four in line, often as not, the end one is wired as a driver, so will read different from the others. Pull the four and read them individually.

TheMJ15003 will drop into place with the 6357s. MJ15022s would work, but you'd want to replace all four so theyt share current well. Mixing 15022 and 15003 is not right.

[Axtman]

Thanks guys. I will buy the real McCoy from Mouser and will replace all four on one side.

In the mean time I stumbled across some good articles on fake transistors. (Who thought there was money in it?)

Counterfeit Transistors

[Enzo]

Oh we have entire threads about it here.

[mhuss]

Peavey themselves ... [cross reference sheet]

I love the note at the bottom of the sheet: "Note: Save good devices left over for future use."