SJ4353 Output transistor replacement

[Memphis]

Wondering if a 2n4348 will work in place of the SJ4353. The only reason I ask is I have a few goods one lying around for testing.

[Enzo]

SJ numbers are house numbers, so without information about what the product is that uses them or the schematic, it is hard to say.

[Steve Conner]

See the Peavey transistor cross reference. It's a sticky in the Schematic Request forum, and will tell you what the manufacturer's part number was.

[Jazz P Bass]

The SJ4353 is basically a 2N3055.

[Enzo]

Hey, c'mon...

WHAT'S IT FROM???


WHO USES THAT NUMBER?

[Memphis]

It's a Crate CR-IIR I also believe the speaker to be blown. I ordered replacements and we will see when they arrive.

Thanks for the replies

Bruce

[Steve Conner]

I always thought the SJ numbers were Peavey's house numbers. Are we saying that it's the other way round, Motorola used the SJ prefix for all of their customers' special parts?

[Enzo]

I don't know that everyone got SJ numbers, certainly Crown got their own numbers on Motos, not SJs. But I do know that Moto put SJ on parts for other companies besides PV.


Looking at the CR11 schematic - wow, 1979 - sure enough SJ4353 right there in toner and white. So SLM got some SJ numbers. I can guarantee they didn't get those from PV. The SLM part number for that type was 96-355-01, and knowing something about their part numbers (as in "503" in the middle of a 50k pot part number) that 355 suggest to me these might indeed be the 2N3055s that Jazz mentioned.


AMp has +/-27v rails, says it is a 60 watt amp. The circuit is about as basic and by the book as it gets. The output pair in quasi, TIP29/30 drivers, a couple limters, the VAS, and diffy pair. Three diodes for bias, 100 ohm pot across one of them.

[R.G.]

Just as a note about the semiconductor world and its history in general.

Baking semiconductors is a statistical process. You design masks, overlays, etc. and then diffuse doping gases into the blank silicon wafer with heating in an oven. The concentration and pressure of the doping gas, the oven temp, the baking time, and to some extent the wafer purity and basic doping all have some variation, as do all the processes involved. Semiconductor makers spend a lot of money and time trying to get it to happen the same way every time, and still have random variation. They then "test out" the outer edges of the distributions so that the ones that are not fast enough, high enough gain, etc, etc. are removed from what they ship. Today's processes are much tighter than they were back in the 60s and 70s. Back then, the makers would sort everything into gain/voltage buckets and then stamp the ones in each bucket with a different part number.

For a price, the would take a high volume customer's money to make a "Crown Amps" bucket and stamp those with the customer's special number. For a somewhat lower price, they would take a pre-existing bucket, re-test it to meet a customer's need for more volts/amps/speed/whatever, and stamp those with a number different from the generic numbers. It was rare, if it ever happened, for the semiconductor makers to process entire wafers for one customer. It cost too much to get the highly-tweaked fab process dinked over to the custom recipe, then returned to the normal production.

These are my personal guesses, as I was never there when this went on. But they do match what I know of the semiconductor fab industry, and I have had friends that worked there and told me horror stories.