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Old 22nd October 2008, 10:21 PM   #21
hakentt is offline hakentt  United States
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I installed the 330 ohm resistors just like you said, and I went to test the amp, the amp powered up but I heard something give and there is no sound output. I teared the amp appart again and around the area of the resistors it is darkened, something is shorted there.
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Old 22nd October 2008, 11:10 PM   #22
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Generally, when the regulators fail, they destroy most of the op-amps. Sometimes, the damaged op-amps can load the regulators and cause them to fail. Repairing the regulators is generally only about 1/4 of the work to get the amp back running.

With the amp powered up, you need to measure the voltage on the op-amps to confirm that the regulators are producing 18v. If so, you would then need to find what's loading the regulators.

Many times, the defective op-amps will run much hotter than normal. Rarely, an op-amp will become a dead short and won't allow the regulators to produce any voltage. Those can be more difficult to find because they don't run hot.

Are the resistors you used 1/2w or larger?
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Old 22nd October 2008, 11:22 PM   #23
hakentt is offline hakentt  United States
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The replacement that digikey superceded the ssp45n20a fet drivers is wrong and I had to put back the original ones, and replaced again those Q transistors and now it all works fine. So the 500D is done. My other 500D that I fixed before has some major capacitor leaking, the whole board is wet. Whats going on

What would be a good replacement for SSP45N20A?
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Old 22nd October 2008, 11:54 PM   #24
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Which group of capacitors failed?

I use IRF3415s when I need outputs in those amps.
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Old 23rd October 2008, 12:14 AM   #25
hakentt is offline hakentt  United States
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the big ones, fluids leaks out of them
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Old 23rd October 2008, 12:26 AM   #26
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Are the tops of them swollen?

Are you sure it's coming from the caps?

Excessive ripple current or excessive voltage would be two possible reasons for them to fail.
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Old 23rd October 2008, 12:55 AM   #27
hakentt is offline hakentt  United States
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the amp works fine, caps have this plastic cover and it looks swollen and you can press with finger on the plastic and it goes down a bit.
Anyway, can you help me with the MTX 152, I can't seem the find what resistors are the ones that burned up
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Old 23rd October 2008, 01:01 AM   #28
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I have no information on the 152. I've never had one in the shop.

Did you try to get the values of the components from the other channel? They should be identical. R3xx should be the same as 2xx in the other channel.

If the tops are not swollen, it's unlikely that the liquid came from the capacitors.
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Old 23rd October 2008, 02:18 AM   #29
hakentt is offline hakentt  United States
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Ok, I will let you know
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Old 23rd October 2008, 03:08 AM   #30
hakentt is offline hakentt  United States
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can IRF640N be used instead of IRF540?
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