Jellybean TO-3 Transistors

[PotatoBox]

Hello everyone,

I've inherited a large lot of TO-3 transistors from a local hifi repair place that closed down and I'm going to send a friend a small assortment.

He intends to use them for guitar amps, but I have no idea which ones would be ideal for that application. I'm really only familar with the 2N3055, but not much else.

Thanks,

[james_s]

If they came from a hifi repair place I would guess most of them are useful in one way or another in amplifiers. It would be helpful if you put together an inventory and post it, TO3 parts are a lot harder to find these days so it's possible you have some that will be sought after by somebody to repair some old equipment.

[PotatoBox]

I’ll definitely have to sort through it. There’s perhaps half a bucket full of them

[TimFox]

Sometime around 1970, Motorola came out with some good PNP power transistors in TO-3 to match the existing NPNs, and then other manufacturers came out with TO-3s that were good for audio amplifiers.
If you are lucky, the bucket of TO-3s will have either 2Nxxx (US) or 2Sxxx (Japan) numbers, so you have a good chance of finding the data sheets.

[Gyro]

Keep an eye out for any Hitachi lateral MOSFETs (or even VFETs) and if you find any, separate and store them with proper anti-static precautions. These fetch high prices these days.

[PotatoBox]

I’ll keep an eye out for those. Unfortunately he’s started closing up shop and they’ve been outside for a few days now and been rained on before I fished them out of the dumpster. Hopefully none are damaged.

[Gyro]

An advantage of hermetic packages over epoxy. 

(Just dry them out before they rust).

[T3sl4co1l]

2N377x, MJ150xx, etc.?

The 377x are really just bigger 3055s, pretty shite spec, long since filled (since the 80s) by modern epitaxial designs (with reasonable fT and hFE, and good Vce(sat)).  They keep selling them under the same part number, because, well, it's a shite spec, anything will do... and people keep buying them for some reason, so why not.

Maybe some 2N605x and such, among Darlington types.  Kinda not great for audio amps (slower) but often usable.

What kinds do you have (if it's feasible to list off some/all)?

Main things are if they handle enough current and voltage (upwards of 100V 5A), have reasonable gain and bandwidth (hFE > 20, fT > 1MHz say?), and useful DC SOA (say >50W dissipation at Vce > 60V).  It's the last one that you won't see on high voltage / switching types (for CRT horizontal / line output, power supply, etc.), and that's basically it.  Speed and power are bonuses, but can make them harder to use (stricter heatsinking, prone to oscillation).

Like the uh, top performer these days I think, is probably this pair, and similar parts by onsemi and Sanken:
https://www.onsemi.com/pdf/datasheet/mjl21193-d.pdf

Don't forget low-noise / input stage types (usually BJTs, sometimes matched or monolithic pairs, sometimes JFETs too), driver/VAS types (higher voltage, few watts, reasonable speed), and MOSFETs (in particular, lateral MOSFETs are quite sought-after).

A lot of MPSAxx types were common for preamp/input stuff, and things like MJE340/350 are common for VAS.  Not that any of these are really worth much (or very well specified in the case of MJE340/50), just necessary.

A few VAS types aren't so common anymore, like the high voltage, high speed 2SC3503.  Commonly used for high-res CRT video drivers (so, now quite obsolete), PNPs (2SA1381) even less common I think.

Not really anything to say from glancing at a pile, without having memorized a bunch of part numbers -- really just, spend some time looking up datasheets and seeing what kind of range of parameters you have, if you can.

BTW, aside from these parameters (gain, ratings, speed, power handling, package), there isn't really much variation between parts.  Less commonly, Vce(sat), hFE at very high or very low currents, inverted hFE, Veb, etc. can be important, but not usually for stuff like audio amps.  Well, noise, for input stages like I mentioned.  And RF parameters, on relevant types, but you'll rarely see such those on general-purpose or power types.  Anyway, just to say: don't buy into hype like, "X transistor has better linearity and sound stage!" -- linearity is all about the circuit, transistors by their nature are rather nonlinear to begin with, and that varies extremely little between individual parts (actually quite shockingly little, the exponential curve is quite reliable across BJTs).

Tim

[CaptDon]

I was lucky enough to harvest a bunch of C.R.T. neck boards from a local t.v. repair place before they broke the necks off and sent the stuff to the crusher/landfill. I knew those high voltage NPN and PNP transistors would be handy some day. Got lots of 1KV and 3KV ceramic caps also.