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Old 25th December 2007, 01:19 AM   #121
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I'm thinking this may be a long dead thread, but it's new to me
I'll be replacing the + fet rail, and one resistor on my 2150 m rev. D. So I should be getting the IRFZ44N fets, and the gate resistors should all be replaced too?, my R30 is burnt, that's the gate resistor right?
Also, do I need to test the two diodes that go into the fet circuits ie cr19 and cr20 from profuse's picture? How do I test them. One more thing, I have two other resistors that don't read at R5 and R38, are these on either side of the PWM? How do I test that and what does this tell you about why my amp shut down?
TIA

p.s. Part numbers would be helpfull as I don't remember the resistor band codes right now etc.

HereticND
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Old 25th December 2007, 09:09 AM   #122
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What do you mean by "I'll be replacing the + fet rail"?

If the power supply isn't blown, you should leave it as it is.

R30 is an emitter resistor in the audio section. If it's defective, the transistor connected to it is also probably defective. If that's the case, you should replace all 4 emitter resistors and all 4 output transistors for that group of parallel components.
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Old 25th December 2007, 07:25 PM   #123
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Quote:
What do you mean by "I'll be replacing the + fet rail"?
The mosfet on Q14 or Q15 isn't reading so I assumed from this thread that I had to replace all 15 on that side, which I think is the + side?

Quote:
If the power supply isn't blown, you should leave it as it is.
OK, if one mos fet is bad, then you have to replace them all right?

Quote:
R30 is an emitter resistor in the audio section. If it's defective, the transistor connected to it is also probably defective. If that's the case, you should replace all 4 emitter resistors and all 4 output transistors for that group of parallel components.
OK, if R30 is an emitter resistor, where are the gate resistors? Where are the transistors connected to it, cr 18, 19 & 20? Any guess on what to do with R5 and R38?
Thanks for the help!
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Old 26th December 2007, 02:06 AM   #124
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Q14, Q15, Q16... are BJTs not MOSFETs. You need to replace at least 4 of them. BJTs have no gates. Instead, they have bases (base, collector, emitter instead of gate, drain source). Look up the datasheet for the transistors and it will show you the pin configuration.

It appears that Q14 is a driver that drives Q15-Q18). You can confirm this is you find that the emitter of Q14 goes to a group of resistors and from those resistors to the bases of the output transistors (Q15-Q18).

The emitter resistors are connected to the emitters of the output transistors.

If you have parallel components and one fails, you need to replace all of the components in the parallel group. Q15-Q18 are in parallel.

CR18-CR20 appear to be biasing diodes. It's unlikely that they have failed. You would need to set your meter to diode-check to test them in the board.

I can't find the resistors R5 and R38.
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Old 7th January 2008, 09:12 PM   #125
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So what would be the part #'s for the Q14 - 18? Also the other resistors are to the right, towards the middle of the amp, on either side of a chip. Where's the code for resistor lines?

Thanks.
HereticND
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Old 7th January 2008, 09:30 PM   #126
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What are the numbers on the transistors?

If you can't read the numbers, wipe some of the white heatsink onto the face of the transistor. When you wipe it off, you should be able to read the numbers clearly.

If the resistors are red, red, silver, gold, they are 0.22 ohm 5% tolerance. They are probably 2 watt resistors. When you order the replacements, measure the resistors in your amp and purchase resistors that are the same size.

If you want to learn more about the color code, read page #39 of my car audio site or search the web. There are many sites that have this information.
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