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Old 22nd June 2014, 10:43 PM   #1
TX98Z28 is offline TX98Z28  United States
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Exclamation Mono Amp Hissing Really Bad & Humming/Buzzing

Hi all,
I'm new here, and I just purchased a used Memphis 16-PRD1000.1 from an online seller off a big auction site. We'll let's just say the amp has some problems it's not so post to have so I'll make a list of what I've found so far when I looked at the internals.

1. A 100V 33uf capacitor kinda by the RCA inputs has the top partially opened up on it (can see cloth stuff).
2. There is a very loud hissing sound coming from either the main transformer or a capacitor by the transformer it's a really load high pitched hiss that almost sounds like static, and I can hear it from a good 15 feet away.
3. The main transformer sometimes makes a humming and a buzzing sound but, comes and goes.
4. The Relay in the amp clicks after being turned on, takes about 5 seconds and clicks off when I turn the amp off.

Things that appear normal I will list here.

1. No signs at all that anything is fried no burn't FET's, resistors, anything I can see so far.
2. The Relay in the amp clicks after being turned on, takes about 5 seconds and clicks off when I turn the amp off. I'm guessing this is normal my old Pioneer SX-737 does the same thing and works flawlessly.
3. The power LED turns on when I turn the amp on. And off when I turn the amp off.
4. The internal cooling fan turns on when the amps on and off when I turn the
amp off.
5. When I turn the power supply I'm testing with (13.8V 25A Switching Power Supply) on then shut it off real quick then turn it on again real fast, the amp goes into Protect Mode as I believe it should as I'm creating a surge. The fan stays On, and the Hissing Buzzing Humming Sounds All Stop.

This Is all Iv'e tested so far as my DMM needs a new fuse that I can't get locally. Im stumped to be honest. My Memphis 16-PRD500.1 that I also have, is completely silent, so I don't know whats wrong with the 16-PRD1000.1 ?

All tests were done with just the power supply, and no sub hooked up or rca's pugged in.

Last edited by TX98Z28; 22nd June 2014 at 11:03 PM. Reason: Forgot to mention
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Old 23rd June 2014, 02:12 AM   #2
TX98Z28 is offline TX98Z28  United States
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Can a Mod move this thread to the car audio section, I think this thread needs to be there instead of in this section. Thanks.
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Old 24th June 2014, 12:45 AM   #3
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Replace the capacitor. For the hissing, it means the amp isn't holding voltage regulation. The filter capacitors are probably dried out (the big black ones). Replace the yellow ones, too. It seems like this amp maybe suffered a bit of abuse...

Check the fan while you're in there - it should spin freely and without wobble/noise.
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Old 24th June 2014, 01:51 AM   #4
TX98Z28 is offline TX98Z28  United States
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Thank you for taking your time to help me out.
When the amp arrived the gain on it was turned pretty high and the bass boost was at +18db
Looks like I'm going to be busy as this is my first amplifier troubleshoot replacement project. The amplifier was so post to be in perfect working order looks like I got scammed by the seller I bought this from.

If I post up a pic of the amps internals can you give me a brief walkthrough of the internals?
I'm trying to learn how this amp works and whats what with the main components.
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