Peavey Heritage driver transistor 6465 sub?

[1ampman]

Got this Heritage in with 60 cycle hum & distorted output. Replaced the E-caps/no difference. Found a bad driver. Saw some replacement at Antique for $20 each. Seemed out of line. Any suggestions/help would be appreciated. I'm not in my comfort zone...... would really like for this to work out...

[Mick Bailey]

I have them as MJ4247. Now obsolete, but you can cross reference them using alltransistors.com (it gives 462 equivalents).

[glebert]

Happy to be corrected on this, but if I am changing to a different transistor I think it is OK (maybe even preferable) to go a little higher power, voltage, current, but think the bandwidth Ft should be the same for stability purposes. It looks like when alltransistors list equivalents the Ft is done as a minimum so you will get suggestions that are much higher bandwidth.

[Enzo]

Did you contact Peavey parts department and ask if they are selling a part for that at the present time?

I would wager that a nice TO220 MJE15034 would likely work just fine, as it does on a Music Man amp of similar size.

[Mick Bailey]

I take your point about stability and bandwidth, though usually an amp will have some stabilizing caps or be self-limiting by way of circuit design to make device selection less critical. Maybe I've just been lucky over the years, but I haven't had a problem with near-equivalents - even when converting from Ge to Si.

[The Dude]

This might help.

peavey cross reference.pdf

[Enzo]

Yeah, that just tells you MJ4247... so who has those?

[The Dude]

Discontinued (I know), but at least you can then find a datasheet for comparison? Also posted for future reference.

[g1]

A previous discussion about the same part:
http://music-electronics-forum.com/t11161/

[potatofarmer]

Thought I found the reference here originally, but I fixed up a Heritage with a pair of MJ15022G and a pair of MPS6531 a few months ago. It's still working fine, but I don't play it much.

Yep, here's the thread: http://music-electronics-forum.com/t41456/

[1ampman]

The only transistor I can find in TO-3 is the MJ 15022g from Mouser....16amp 200v.... think that will work/ hold up? I've spent hrs on google with no luck. Although Enzo liked the MJE 15034 220/case. Not sure how to mount a 220 in a TO-3 heat sink. Thoughts??? These are $5 each not $20

[J M Fahey]

Please post the schematic.from what I found, MJ4247 is nothing special, even a common 2N3055 matches those specs, go figure.

Read a comment about biasing, but can say nothing until I see a schematic.

Is the original TO3 plastic or metallic?

[1ampman]

The original is a Motorola metal unit, mounted on a nice heatsink. The MJ4247 has been bought up so maybe that's why Antique wants $20 each? The transistor drives a pair of 6L6s through the cathode. I'm told similar to a Music Man. Still my question remains....

[52 Bill]

My guess is that Enzo was writing without having a schematic in front of him and his suggestion of a TO-220 part was from memory.

The MJ15022 should work fine for you here.

[Enzo]

No, my suggestion is from having the almost identical circuit on a Music Man doing just fine with the TO220 part. If MJ15022 works, then fine, it works. But we are now using a 16A part. For a pair of 6L6 each. Like riding around in a semi truck to go to the store for milk.

Even the original MJ4247 was overkill at 120v 8A. 2N3055 has all the excess current, but 120v is beyond many of them, if not most. Yes, the original is a plain old metal TO3.

The $20 is for original Peavey parts from the third party vendor. You can buy subs a lot cheaper yes.

The MJE15034 is a 4A part, more than enough current. And at 350v, no worries from the tube circuit. You could use a lower voltage part from the MJE1503x series, but why bother? If you prefer, you can use the MJE15032 which is an 8A part at 250v. All the overkill of the original part

How to mount one? Bolt it to the heat sink and fly wires to the board. With luck you can bend the outer legs down into the TO3 pin holes.

I have replaced these in the past, but I do not consider the circuit unreliable at all. But that 120v spec always bothered me. The cathode sits at 75-80v at idle, so I worry about peaks exceeding the 120v spec. Perhaps i am overly cautious.