Acoustic 906 Mixer/PA problem

[rf7]

This guy folds up on the positive going waveform without a load, so I want to replace the 40409 driver transistor with a 2N3440. If I do that, do I also need to replace the (working fine) complementary 40410 driver with a 2N5415? Or will the 2N3440 be fine working with the 40410?

Thanks in advance!

[Enzo]

The push has no idea what the pull is doing, and vice versa. This is a solid state amp, which means it is massively fed back, and will go down trying to correct any distortion. So no need to replace everything.

MAgic Parts still lists 40409 and 40410 in their catalog, and though I don;t see it in CEDist, I THOUGHT AES sold them too. Under $7.

[gbono]

I would just press out the defective transistor and carefully ream out the hole in the heatsink and press in the 2N3440. Haven't seen the old RCA parts anywhere under $10 when you include shipping.

[Enzo]

You can certainly do that. If you are a hobbyist, you have plenty of time. My customers are paying $1 a minute or more, so my outlook reflects that. If it takes me more than 10 minutes, I might as well have spent the $10 and used the 10 minutes elsewise. And for that matter I have a bunch of the real parts in stock. No, I don;t want to sell them.

[gbono]

So what's the plan when you can't get any more 4040x from MusicParts, etc etc?

[Enzo]

Then you do what you have to do. When my supply runs out, and theirs runs out, then your plan is exactly what I'd do.

That is why I don't want to sell mine, each one of them is not a $10 part, it is a $75 repair bill I can make.

Nothing wrong with your part modification approach, my context is not everyone else's context. I know a guy who needed a foorswitch plug for an old Gibson (I think) amp. One of those several pin things. He is a luthier, so he took a block of maple and formed the body of a connector, drilled holes and glued in pieces of brass rod stock cut and rounded on the end for pins. made a little cover for the back and soldered a cable to it. The guy MADE a connector. My hat is off to him and it was lovely work. I couldn't justify doing something like that, but to him it was a nice project that took all afternoon.


And you are right, $8 shipping makes a $4 part into a $12 part. I have the luxury of adding such a part to a general order. WHen I get a couple quads of tubes and a reverb pan, adding a couple transistors doesn't up the shipping.

[gbono]

I have two polytone mini-brutes (circa 1980) that I'm bringing back to life. Talk about parts unobtainium. Ah but that's another topic.