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Old 28th January 2006, 10:36 AM   #21
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Bad news, i accedently blew an output transistor because its heatsink came in contact with the other ones emitter resistor.

What do you think about using two of these: http://pdf1.alldatasheet.com/datashe...N/STA434A.html as output transistors pressed against a heatsink ?

They are from a stepper driver, but i think they should work for audio too, tho they are darlington but i donīt think that should matter.

What do you think ?
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Old 28th January 2006, 11:09 AM   #22
lineup is offline lineup  Sweden
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Quote:
Originally posted by Tekko
Bad news, i accedently blew an output transistor because its heatsink came in contact with the other ones emitter resistor.

What do you think about using two of these: http://pdf1.alldatasheet.com/datashe...N/STA434A.html as output transistors pressed against a heatsink ?

They are from a stepper driver, but i think they should work for audio too, tho they are darlington but i donīt think that should matter.

What do you think ?
I say you should not (can not) use those.
It is a totally different type.

Replace with original BD139/BD140, or MJE340/MJE350 which are in same TO126 class.
Eventually you could try some TO220 transistors, for example MJE15030/MJE15031.

And use your amplifier only for headphones.
To modify for driving loudspeakers, you need some experience to know what changes to make.
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Old 28th January 2006, 11:29 AM   #23
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I know its an other type, its a darlington H-bridge but not connected to each other so i can easily hook them up as they were normal single darlington transistors.

I donīt have any of the transistors u suggested.

But if someone has a few over iīll gladly take them.

The amp gladly drives speakers as is, i have played it loud and it doesent even get warm.
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Old 28th January 2006, 11:40 AM   #24
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Now i have changed the broken transistor with a to220 i had in the transistors box, a 2SC1173 and it works perfectly, it doesent even have a heatsink and it barely gets warm anyway.
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Old 28th January 2006, 11:50 AM   #25
lineup is offline lineup  Sweden
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Glad you could make it work.
I would at least put a little piece of aluminium as heatsink at that power transistor.
Just in case.
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Old 28th January 2006, 12:01 PM   #26
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If i find a BD139 (2SD669) i gonna change the heatsinks to prevent further accedents.
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Old 28th January 2006, 12:16 PM   #27
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I found a BD135, close enough ?
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Old 28th January 2006, 12:36 PM   #28
Nisbeth is offline Nisbeth  Denmark
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As long as the voltage isn't too hiogh for the 135 (check the datasheet), no problems


/U.
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Old 28th January 2006, 01:21 PM   #29
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The amp sees a total of 24v, 2x12v rails.

Now i have mounted the amp onto a bigger heatsink.

Click the image to open in full size.
Click the image to open in full size.
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Old 28th January 2006, 11:50 PM   #30
Nisbeth is offline Nisbeth  Denmark
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In that case, the BD135 should do just fine


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