Need transistor source. sorting out Audix 35102 headroom

I'm working on a project with the help of some other folks here on the forum to make some pcb's that will help to rectify the headroom issues on the Audix 35102 modules. More or less, we're just going to re do one of the output stages of the 35302, but in a smaller package for rack mounting. After tests, these 35302 modules seem to be helping to dramatically put the 35102 modules back in proper order and drive a 600 Ohm load properly a relieve headroom problems on the output stage. We will be offering the PCB's up on the forum too for those interested.

Anyway, I'm trying to locate some of the transistors for these modules and am having problems finding them someplace where I don't have a $300 minimum order. Mouser and Digikey don't seem to have them either. Can anyone help? Here are the transistors:

BC413 X 2 (TO-92 package)
BC415 X 1 (TO-92 package)
40871 x 1 (TO-220 package)
40872 x 1 (TO-220 package)

Otherwise, anyone interested in a group order for any of these transistors? If I can get $300 worth I do have a source.


Cheers,

T

bump

I don't get it. Are people content with their halfway functioning Audix modules?

This deserves a bump.

I'd take at least one of these boards and transistors for it. This is a worthy project.

These transistors are proving hard to find:

40871 x 1 (TO-220 package)
40872 x 1 (TO-220 package)

Anyone know of modern equivalents?


I've found what are supposed to be modern equivilents for the others (BC413 and 415), but have yet to try them out. We've had a delay with some stolen gear today, so it will be at least a week or two before anything really moves forward with this.

T

Tillman,
I've got some 35302s that I could pull your transistors from, but only about 4 sets.

peter

Peter,

Any help is good help in this situation! Let me get back to you after we do some more tests with actual instruments to ensure that the 35302's are doing what we want. Like I wrote, we've been delayed with an unfortunate theft by some assholio. Hopefully we can get back on it next weekend, but we'll see how it all works itself out. If they are doing what we want, I would love to get those transistors from you.


Cheers,

T

Howdy... just thought I'd pop in here and say hi !

Tillmann and I are going to try and get a little board made up to help out with the load driving issues on the stock 35102, but these transistors are turning out to be difficult to find.

[quote author="Tillmann"]These transistors are proving hard to find:

40871 x 1 (TO-220 package)
40872 x 1 (TO-220 package)

Anyone know of modern equivalents?

T[/quote]

You should be able to use BD243D (or BD543D) instead of 40871 and BD244D (or BD544D) instead of 40872.
In case you have any japanese transistors around you can use 2SD550 (or 2SD866) instead of 40871 and 2SB870 instead of 40872.

Just found all needed transistors at Cricklewood Electronics.........
http://www.cricklewoodelectronics.com/Cricklewood/customer/home.php

But they're greedy bastards.

Thanks Peter, I emailed them and about 10 other suppliers earlier in the week that said they had them. I never heard back from any that said they could get them to me.

T

Thanks for starting this. I am very interested and I'll do whatever I can in my limited abilities to help.

coolio, Charlie. At this point, the only stumbling block are the transistors. Before anyone goes crazy, we need to do another test with some instruments rather than just talking into a 57 or 58. If they perform well, then any help finding those would be great. It would be cool if someone could try out some of the new replacement transistors in a PCB to see how it performs, that way people who want it don't have to hunt for vintage transistors. But like I said, I'll get back after we've had a chance to test the 35302's in the circuit again. The PCB layout is close to done already, I think.

T

Jayzus... don't you septics have free international calls yet?
If you want me to take care of things, just let me know.

peter

Thanks Peter.

I'm in the process of making a PCB layout. I successfully wired up a 35102 and 35302 today and bench tested it. Tillmann and I should be meeting up sometime next weekend to test it out on some instruments and some screams. If the tests are successful I'll really get cracking on finishing the PCB layout.

[quote author="peter purpose"]Jayzus... don't you septics have free international calls yet?
[/quote]

:grin:

How did you know my name was Jayzus?


Cheers,

Jayzus

All this Audix talk got me inspired to pull out my 35102's and the 35302 that I recently got my hands on to see if I could get them working together. I wired them all up and upon testing they passed clipped audio.

I decided to take the 35302 out of the equation and listened to the output of a 35102 on my Qbox. Still clipped audio and I noticed on the Qbox voltage checker that there was voltage on the output. Uh oh, I guess I'm also in the market for BC413's and BC415's. I apparently cooked them trying to drive transformers with them a while back. Live and learn, I guess. But I could swear I've seen pictures of 35102's racked up by themselves with output transformers more than once ...

Anyway, here's what I came up for for a pinout for the 35302 if this helps anyone, or if anyone can offer corrections, please do.

10/11 - 0v.
22/23 - +24v.
41 - chassis ground
7 - input hi, line amp A
8 - input screen, line amp A
15 - output hi, line amp A
16 - output screen, line amp A
33 - input hi, line amp B
31 - input screen, line amp B
27 - output hi, line amp B
28 - output screen, line amp B

Tie 10 & 11 together
Tie 10 & 41 together
Tie 22 & 23 together

I have a racked pair of 35102's and I KNOW they don't have an output stage - just the class-A TO-92 that is part of "Circuit 5". Correct me if I'm wrong, but in circuit 5 VT152 (BC415) is a current source and VT153 (BC413) is the actual output "driver". I don't think it would take much of an output stage to bump this up a few dB and give some current capability. I don't use the 35102's very much, but I have yet to damage the output section of circuit 5.

Is it really necessary to use all of the original devices? I don't think that any of these old transistors are all that special and there are modern equivlanets that are readily available. Here in the US, it is impossible to find the TO-220 transistors that were used in the output of the 35101's, and I'll bet that the output circuit is nearly the same as the 35302's output circuit.

I don't have a schemo for any of the Audix stuff that contains a good driver circuit. Can anyone direct me to one so I can see how they did it?

Tim

I got thrown off because the schematic shows BC413 and BC415 transistors for the output (circuit 5) but my 35102's (V.3) actually have BC441 and BC461 in their place.

I had my 35102's hooked up to 600:600 transformers and they seemed to work fine that way (albeit with low output) for many months. I hadn't used them for a long time and just this week fired them up to do some testing with the 35302 and found that the output transistors were bad. I'm assuming that it was because I loaded them down too much with the transformers.

The equivalent transistors for BC441 and BC461 are 2N3053 and 2N4037.

I have pictures for the 35302 but they're from a large diagram and cut up into sections. I'll put them up if no one has a better copy. Tillman had posted a 35302 schematic a while back which I was too slow to download and now it seems to be gone.

I personally don't think it's necessary to use all original devices for this task. Brian Roth made an opamp circuit solution for this that I'm sure works fine. For me, I guess it's just a project. I don't think these are quite magic boxes, but they do sound pretty good. I think there's something to be said for the original design.

As I wrote already, there is a quoted modern replacement for the BC413 and 415 that I have not yet tried. I've been unable to find a noted replacement for the 75801 and 803 or whatever number they are. One person suggested a model. I've not tried it. Greg and I are going to provide the PCB's. Feel free to help test out some modern equivalents.


Cheers,

T!

Audix line amp

35302_amp_schematic

35302_amp_block_a

35302_amp_block_b

35302_amp_block_c