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Old 16th May 2011, 06:23 AM   #1
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Default Rockford Fosgate Power 50M

Hello everyone. I have an amp that is giving me some trouble.

It is a Rockford Power 50M, board number PC-1041-E.

The initial complaint was low output. I viewed the output through the scope and it looks clean. Its not putting out the power it should.

There is a capacitor missing in location C116, not sure if it is suppose to be or not.

Also Q106 Q107 (A56) are getting very hot within seconds.

Also Q109 Q110 (A06) are getting very hot within seconds.

The amp produces clean audio and sounds good but the output is low.

What would cause the A56 and A06 to get so hot so fast?

The output fets have been changed and their gates and emitters are within tolerance.

Just wondering where I should look?
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Old 16th May 2011, 06:59 AM   #2
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I don't have anything on that amp. If you have the schematic diagram, send me a copy.
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Old 16th May 2011, 07:04 AM   #3
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I dont have one either, I can e-mail Rockford and they will send it.

Do you have one on a power 50.1 chrome or gray or black and grind series? Same board.
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Old 16th May 2011, 07:44 AM   #4
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OK. Send me a copy if you can't find the problem after you get the diagram.
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Old 16th May 2011, 07:45 AM   #5
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OK. I sent Rockford an e-mail they will send it to me tomorrow. I will send you a copy just so you have one anyways.
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Old 17th May 2011, 09:38 PM   #6
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Here is the schematic Perry, I sent it to your e-mail. Wondering if you could take a look and see what you think about the (A56's and A06's) getting so hot.
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Old 17th May 2011, 09:45 PM   #7
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It said the file had an error and wouldnt let me send it to your e-mail. It also exceeds the forum file size for this type of file.
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Old 17th May 2011, 10:25 PM   #8
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I was able to forward the e-mail they sent me to you Perry, let me know if you got it and were able to download it. Might have went to your junk mail. Let me know.
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Old 18th May 2011, 09:20 AM   #9
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Does the amp draw excessive current?

Do those transistors still get hot without Q125 and Q126 in the circuit?

I don't know if Q116 was intentionally omitted but in the 1100a2, the capacitors in that location are in the circuit. You may want to try installing one there, especially if you see any sort of oscillation on the bias transistor.
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Old 21st May 2011, 06:05 AM   #10
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I will check this tonight and get back to you Perry, sorry been real busy. How do I determine if there is oscillation in the bias transistor? By that do you mean the MPSA06 (Q108)?

The amp does not draw excess current, idles fine and produces clean audio. Just has low output and the A56's and A06's are getting very hot.

I will try installing the missing cap, and removing Q125 and Q126.
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Last edited by seankane; 21st May 2011 at 06:07 AM.
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