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Old 20th September 2010, 11:39 PM   #1
chipper is offline chipper  United States
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Default Using different transistor brands in same circuit?

Hi,

I had a problem with one of my amps. How it failed it was because I was positioning it in my trunk the wires were not insulated where they were connected together the B+ was covered aswell as the GND wire, anyways two of the speaker wire and the REM wire was not covered and I was moving the amp around the positive rem wire touched one of the speaker connections and the amp I believe got damaged. Btw it is a Rockford Fosgate Punch 150 very early version. Amp turns on but the output won't play anymore it just makes a click pulse sound through the speakers and that's it. It did smell like something fried inside. And when I checked I saw that the legs of transistors marked 2N6487 M325k, those are the ones were the legs turned gold usually they are silver. Is it possible just those are bad and not the 2N6491's? The real question was: can I use STMicro and ON Semi together? I found those exact parts that are available to purchase. This is a really good amp and i got to admit I am an dumb a** for the mistake i did. So if anyone can give their input as to what i can do to make it play again.

Note: I am limited to electronic testing equipment to use so please bare with me. However I do have access to vom, solder iron, ohm meter and that's about it. Thanks alot. If you also need a picture I can post one....
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Old 20th September 2010, 11:50 PM   #2
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Some of the early transistors had gold plated legs.

The 2N6488 is generally used to replace the 2N6487.

The brand doesn't matter as long as the components with the same part number match in each channel.

You can check the transistors to determine if they're defective.
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Old 21st September 2010, 12:15 AM   #3
chipper is offline chipper  United States
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Quote:
Originally Posted by Perry Babin View Post
Some of the early transistors had gold plated legs.

The 2N6488 is generally used to replace the 2N6487.

The brand doesn't matter as long as the components with the same part number match in each channel.

You can check the transistors to determine if they're defective.
For the gray transistors i get a reading of .456 and the second gray transistor I get .437 (from the metal tab) and .457 with probe on the metal tab. That's left and right. Is this a indication of these being good?
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Old 21st September 2010, 12:50 AM   #4
chipper is offline chipper  United States
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I just found out the left side of the amp is functioning still (glad i don't have to spend the extra $$ for parts) I just removed the speaker fuses from the bad channel amp came out of protect. I'm assuming I shot +12v on one channel and killed the outputs and maybe the driver transistors? Which are the drive transistors on this? Thanks
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Old 21st September 2010, 01:28 AM   #5
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The drivers are probably MPSA06s and MPSA56s if it's the one with the heatsink in the transformer. You can get the schematic diagram from Rockford if you can't follow the traces back from the bases of the outputs to the drivers.
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