Repair folks: what transistors do you keep on-hand?

[nashvillebill]

A while back I started doing some amp repair work on the side. Not geting rich off of this by any means, but I'm picking up a little spending money. Guitar amps and old stereo stuff.

In my area though, other than Rat Shack, there are no electronic parts houses any more. Now I could order stuff from Mouser or Digikey or whoever, but when I only need a single 50 cent transistor?? (For example, right now I need a single 2SD400)

The other stuff--caps, diodes, resistors,whatnot--I've got a decent stash to draw from, and a small stash of 4558 and NE5532 op-amps and some 3-legged voltage regs.

But what transistors would be beneficial to keep on hand? I've got some 2222's, some 2N3055's, some 2N2907's and some BC107's but not a whole lot of others. (I like RG Keen's advice, its better to sub a generic transistor than to wait on some unobtainable obscure part to arrive from lower Elbonia.)

What do you guys keep? Thanks!

[Enzo]

Look through the Music Electronics section, we have discussed this very topic.

Interesting that the ones you have on hand are for very old amps.

What do I stock?
MJ15024 and MJ15025 for high power. I also stock MJ15003. That covers most Peavey repairs and the majority of TO3 needs..

Fender and Crate use the TIP142 and TIP147 pair a lot. And Marshall in their Valvestates used to use these BDV64 and 65 types - well, TIP142/147 drop right in their place. TIP142/147 come in several sizes, DO NOT get the smaller TO220, TO218 is the common size.

I stock a number of other power transistors in larger sized (TO247), but really, unless you fix PA amps or things like Hartke modules, wait til you need them.

Having a few TIP41 and TIP42 as general purpose TO220s can't hurt. I like to keep a few MJE15032 in stock for cathode driven tube amps like Music Man and some PVs. 8A 250v NPN

The little half-round ones are TO92 types. There are a million of them. You can find similar parts in the Asian series, the American series, and the BD series. A 2N4401 and a 2SC945 might be interchangable, but the parts have different leg order. SO I stock a selection of both 2S types and 2N types (which includes the MPS series) I stock a few common BD ones, but I use them for specific repairs, I don;t use them generically. Nothing against them, I am just not as familiar.

MPSA92 and MPSA42 are 300v 0.5A types useful for higher voltage use.
MPSA06 and MPSA56 are lower voltage general use types.
2N3904 and 2N3906 - can't go wrong having those around, they are a sort of standard low voltage experimenters part (40v 200ma) And cheap. MOuser sells them for as low as 2 cents

A word about volume purchase. You don't have to be General Motors or IBM to buy in quantities. Look up 2N3904 in MOuser, I can scroll down and see one selling for 12 cents each. That's cheap, but look at 25 lot, if you get 25 of them, it drops to 5 cents each, and below that, if I buy 100, i get them for 1.9 cents. So I can but 10 for $1.20, or I can buy 25 for $1.25, or 100 of them for $1.90. Now I like 2N4401 a lot too and various others, but in general, turning on an LED doesn't much matter what you use, so I might consider bulking up on fewer types. PArts often have price breaks at 10 or 25 pieces. SOme as low as 5 pieces.


There may be specific transistors that would be good to stock. I used to do a lot of QSC repair, and there were certain tansistors I used all the time. Now I do less of that, but those transistors still are useful as subs. SO I stock a bunch of those TIP142 and 147 I mentioned, but a HIFI repair shop up the street might never use them.

Depending on whatyou service, having a few TDA7293 and some LM3886 might be a good idea. Smaller practice amps might use the TDA2040 or 2050.

[nashvillebill]

Thank you, this was VERY helpful!

and yes everything I'm working on is old...like me....