Acoustic 450 missing 40409HV and 40410HV

[shomyca]

Hi there guys,
I have a Acoustic 450 head that is missing a 40409HV and 40410HV transistors acording to the schematics. The heat sinks are there but without transistors in it

What can I do with this to make this amp work? I read some enzo's and gbono's posts about 2n3440 (npn) and 2n4033 (pnp) placing in the heat sinks... Everything else on power board seems to be original so can I just put these two 2n transistors in the heat sinks and turn on the amp?

Thanks
Milos

[gbono]

You might want to remove the output transistors and check them with a DMM. Wouldn't hurt to use a light bulb limiter or variac to turn this amp on for the first time.

[shomyca]

Thanks for reply gbono,
I called the guy who gave me the amp, he says that he took out the transistors from the heatsinks. He needed the transistors but he tought that heatsink is part of the board not part of the transistor

He also says that before he done that amp worked perfectly and that everything else is original. And that is true, I checked it radically.
I even took out the 40409 and 40410 from my 126 combo to try it out and it worked nice.

Now, can I return the old heatsinks with 2n3440 and 2n4033 in it and power the amp. I am not a technician and don't have bulb limiter or Variac so if I wouldn;t supose to do this, if there is some risk, than I would bring the amp to some tech around.

I am from serbia and I don't trust these techs around and because of that I posted this thread. Cheers

Milos

[gbono]

Milos,

Glad you could fix your amp. My Mother is from Slovenia. It's a small world.

[shomyca]

Milos,

Glad you could fix your amp. My Mother is from Slovenia. It's a small world.

But... I didn't fix it. I just tried with another 40409 and 40410 from another amp, and I returned those in that amp, acoustic combo 126. THe 450 head still remains without them, 40409 and 40410 and I'm still wondering if I can put back the old heatsinks with 2n3440 and 2n4033 in it and power the amp...

And yes, world is small ineed. I got great friends in Slovenia. Beautiful country. I bet it is better place for acoustic amp than Serbia

[52 Bill]

I know that we've discussed this many times before, but here are few numbers for replacing the RCA 40409 and RCA 40410 transistors.

2N5320/2N5322
2N5681/2N5679
2N3440/2N5415

These are complementary pairs, one NPN and one PNP, so be sure to watch polarity.

None of these transistors come with the built-in heat sink, so one will have to be added.

It may be possible to reuse the dead 40409/40410 transistor's heat sink, by knocking out the original TO-39 and soldering in the replacement transistor.

If using a different heat sink, you may need to add a jumper to the board, as the original heat sink is often used as a power supply common connection.

Other transistor types in TO-220 cases can be used, but the pinouts are different and will need to be installed carefully.

[shomyca]

Thanks for reply Bill,
So from your replies I see that It is not quite safe for amp to power it with replacaments without precaution... Am I right? I should bring it to some technician, yes?

Milos