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Old 11th December 2009, 02:48 AM   #1
chipper is offline chipper  United States
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Default blown Rockford amp help

Okay, i just purchased a Rockford Fosgate Punch 150a2 and was pretty excited to have one of these and went ahead and hooked it up in my ride and it sounded horrible and popped open the cover and saw that it had a severely blown MOSFET in the power supply section. I can't indentify it because it is badly burned. But, then in the cirstui board it says 120.2??? it has a sticker on the power transformer saying 120.2. Does anyone have one of these? i need to know the MOSFET # to try and fix this. I was gonna request an refund from the seller but i'd rather keep it. Kinda dissapointed but oh well. Also how was this still playing music if it had a blown MOSFET? Is this really a Punch 120.2 or Punch 150a2? I'm sorta confused? Thanks
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Old 11th December 2009, 02:54 AM   #2
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It has two identical power supply FETs. If you can read the other, you'll know the part number of the burned one. Replace them both.

The gate resistor for the burned FET is likely open or out of tolerance.

Sometimes, driving only half of the primary windings will allow the amp to play but it will be at reduced power and the supply will draw more current than it normally would.
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Old 11th December 2009, 03:06 AM   #3
chipper is offline chipper  United States
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Quote:
Originally Posted by Perry Babin View Post
It has two identical power supply FETs. If you can read the other, you'll know the part number of the burned one. Replace them both.

The gate resistor for the burned FET is likely open or out of tolerance.

Sometimes, driving only half of the primary windings will allow the amp to play but it will be at reduced power and the supply will draw more current than it normally would.
Okay i have a question? How do i take the mosfets out? They are soldered on to a smaller circuit board?

And do you know where they sell these mosfets?

Thanks Perry!
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Old 11th December 2009, 03:09 AM   #4
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Post #29 here explains basically what you need to do to replace them.
t30001bd schematics

What's the part number on the second power supply FET?
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Old 11th December 2009, 03:26 AM   #5
chipper is offline chipper  United States
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Quote:
Originally Posted by Perry Babin View Post
Post #29 here explains basically what you need to do to replace them.
t30001bd schematics

What's the part number on the second power supply FET?
BUZ103

Thats the part # for the mosfet.
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Old 11th December 2009, 03:33 AM   #6
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I'd use the Z44 as a sub.
844-IRFZ44PBF (mouser).
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Old 11th December 2009, 03:38 AM   #7
chipper is offline chipper  United States
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Quote:
Originally Posted by Perry Babin View Post
I'd use the Z44 as a sub.
844-IRFZ44PBF (mouser).
Okay so what if this is my first time attemping this? Any advice on how to get these out? I read the post but im somewhat afriad of the torch thing as i don't mind heading down and purchasing one and using. How much time should i keep it on there to remove the FET?
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Old 11th December 2009, 03:57 AM   #8
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You'll have to hold the flame on the bottom of the insulator for 30-60 seconds. Be sure to wait until the solder has melted. When the solder has melted, the transistor will pull away from the insulator with very little force (only the force required to bend the component leads).

Be sure to angle the torch so that no heat is applied to the circuit board.

Don't forget to order the gate resistors. If you don't have any on hand, order the driver transistors also (mmbta06 and mmbta56).
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Old 11th December 2009, 04:07 AM   #9
chipper is offline chipper  United States
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Quote:
Originally Posted by Perry Babin View Post
You'll have to hold the flame on the bottom of the insulator for 30-60 seconds. Be sure to wait until the solder has melted. When the solder has melted, the transistor will pull away from the insulator with very little force (only the force required to bend the component leads).

Be sure to angle the torch so that no heat is applied to the circuit board.

Don't forget to order the gate resistors. If you don't have any on hand, order the driver transistors also (mmbta06 and mmbta56).
Okay so will there be enough solder for the FET to solder back on?

Whichs ones are those?

I got a question? What is CR1, CR2? Are those transistors?
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Old 11th December 2009, 04:21 AM   #10
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CR1/2 are rectifiers.

I'm not sure which board you have but the drivers are typically designated Q1, Q2, Q4 and Q5. They are likely marked 1a and 2a. They will be near the TL494 IC.

You'll have to tin the backs of the transistors with new solder. You'll have to sand the backs of the transistors so they'll take the new solder quickly. The HUF75339P3 is another possible sub and may not need to be sanded to take the solder.
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