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Old 5th December 2008, 01:33 AM   #1
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Default rockford fosgate 550x

Im working on a fosgate 550x. Ive replaced the power supply fets, checked the gate resistors,and checked all mpsa 56's and 06's. When power and ground are applied NO remote the amp draws 20 amps or more of current. Wondering what do i check next im stummped
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Old 5th December 2008, 01:35 AM   #2
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Sorry forgot to metion in last post i checked all outputs, the 317's 337's and u1620's and 1620r's all check fine
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Old 5th December 2008, 02:21 AM   #3
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Connect ONLY remote and ground. With your black meter probe on chassis ground, what is the DC voltage on each of the gate legs of the power supply FETs?

Are all PS FET gate resistors within tolerance?
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Old 5th December 2008, 02:44 AM   #4
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All the gates measure 3.82 volts. the other two legs on all power supply fets read 13.91 volts. the gate resistors all read 10.1 ohms

Further checking in this amp it looks like the torriod got hot at one time and melted the coating off one of the leads.

So wondering where do i go from here?
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Old 5th December 2008, 02:56 AM   #5
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Sorry did that wrong the first time the gates read 10.08 volts.

The other two leads on the fets are 0 volts.

Looks like the torriod got hot at one point it melted the coating off one of the leads.

Wondering where do i go from here
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Old 5th December 2008, 03:08 AM   #6
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If you're reading 10v on the gates, the PNP driver transistors (likely marked 2A) are open. They will be near the TL494.

Is only one turn damaged or do you have multiple turns damaged on the transformer?

Can you post a photo of it?
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Old 5th December 2008, 03:46 AM   #7
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i found a couple 2a's shorted. and heres a pic of the torriod sorry my camera isnt the best
Attached Images
File Type: jpg picture 002.jpg (54.2 KB, 136 views)
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Old 5th December 2008, 03:50 AM   #8
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heres a lil larger pic if needed
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File Type: jpg picture 003.jpg (63.2 KB, 126 views)
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Old 5th December 2008, 03:52 AM   #9
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I can't see enough detail on the transformer.

If only 1 winding (the terminal winding) is shorted, you may be able to desolder it and insulate it with heatshrink tubing or Kapton tape to prevent it from shorting. If there is more significant damage, you will have to get a replacement transformer from Rockford or rewind the one you have.

If you have replacements for the driver transistors, replace them and measure the gate voltage again.
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Old 5th December 2008, 03:55 AM   #10
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Email me the photo at the highest resolution. What camera do you have?

babin_perry@yahoo.com
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