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Old 18th December 2004, 05:52 PM   #1
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Exclamation Problems

Okay i have an L.A. Sound Car Amplifier 200 Watt PCH50 and it got hot blew the fuse and i cant put another fuse in it. Would someone please tell me how to fix it. This amplifier is a pretty good amplifier it has a flat filter, a low filter, and a high filter. Along with the 30hz to 600hz filter control. Also the 0db to +18db bass boost, and the input level control. Someone please reply and help me get my amplifier fixed. If you cant tell me what to check, how to check it, and where to get parts.
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Old 18th December 2004, 11:01 PM   #2
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Default AMP REPAIR

does it blow fuse with no load ?
Tha amp is comprised of 2 sections
1) the power supply
2) The amplifier

You need to be handy with an Ohm meter to atempt a repair.
many times there is a shorted xistor or diode bridge in the power supply, or a shorted output xistor in the amp. visual inspection may reveal a burned trace on PCB .



Jeff
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Old 21st December 2004, 07:55 PM   #3
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I have the amplifier plugged up to the battery and the remote with the ground when i put in a fuse it blows it instantly. I have no idea what you are talking about by resistor or diode i know how to use an ohm meter. I am the type that when something breaks i just buy another one. Im just at the point where i would like to start fixing what ive got. Thank you. Please reply.
David
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Old 22nd December 2004, 10:14 AM   #4
eXn is offline eXn  United States
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I had this same problem and i was going to change the amp because i had an extra but i unscrewed it from the floor and when it was unscrewed i was showing someone what it did and it worked fine. so depending on how it is mounted in your car try taking it out (not unplugged).
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Old 22nd December 2004, 07:21 PM   #5
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Thats just it, it wasnt bolted to the floor or anything it set on top of the carpet and when it blew i finally figured out that there were little vents on the bottom. So i guess it blew an inside fuse because of too much heat. My cousin looked at it and said the amp was sloppy built you cant tell what on the circuit board is supposed to be grounded and what is not supposed to be. He said plug it up and find out how many volts ive got from one side of the fuse to the other side. So we can find out if its grounding out somewhere.
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Old 22nd December 2004, 08:12 PM   #6
maylar is offline maylar  United States
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If you don't understand what resistors, transistors and diodes are then you might as well attempt brain surgery. You can't fix an amp with a screwdriver.

People who are experienced at this would have half a chance because the designs of amp circuits are all similar and they would recognize the parts and be able to take a guess what to look for. I've been fixing stuff for 30 years and I wouldn't even attempt it unless I had a schematic.

I admire your ambition to learn, but you've got a long way to go.
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Old 22nd December 2004, 08:43 PM   #7
Duo is offline Duo  Canada
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I hate to be entering into the obscenities here, and punish me if I go too far:

Maylar: You're a bit cocky there. I may be only 17 years old, however, I have repaired many amplifiers. Many as in thousands. I have yet only needed two schematics, and in most cases, I reverse engineer a circuit and use that to troubleshoot. Rarely have I had an amp that I couldn't repair, be it SMPS problems, blown output transistors, cold solder joints (seems to be the problem most of the time.) But even in more complex situations.

I learned from a 60 year experienced technician that the majority of problems require nothing but sharp attention, an open mind, and a diode/ohmmeter. With eyes, ears, and nose available, you can do great things.

Onto the useful information, if the fuse continues to blow, there's obviously an abnormal path inside where the current is flowing unduly. The first things I'd check are the power supply transistors/rectifiers, and the outputs and drivers in the amplifier section.

Testing a transistor is a rudimentary task and is easily performed by an inexperienced person with a working ohmmeter or meter with diode checker. Each transistor has three pins, the most basic check being to see if any pair of pins shows a very low resistance in either polarity of the leads. This can be misleading, nonetheless, in that some amplifier designs will show this in the circuit with good transistors.

The amplifier section will often be a separate board with large transistors on its edges which are secured to the metal case. The power supply board looks like this as well, but it has a large ring shaped part on it known as a toroidal transformer.

My first observation would be to look for blackened areas and/or parts that look as if they have exploded or burned. It's easy to tell since there will be other parts of the same look in there that aren't burned with which you could compare.

I must apologize but I can't offer more information at the moment, I've got to go. But if you want, please email me and I'll further help you through instant messaging or email.

- Daniel
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Old 23rd December 2004, 04:04 PM   #8
maylar is offline maylar  United States
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You've fixed thousands of amps at age 17?

Like I said, if you know what to look for you have half a chance. But not knowing what the basic parts are means you'd be clueless... ohmmeter or no.

I'm not suggesting that David give up or implying that he couldn't eventually figure out how to fix his amp. I only suggest that he start by learning the basics of electronics first. There are lots of resources available for that.. online, in print, or in schools. Gotta walk before you can run.
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Old 23rd December 2004, 07:03 PM   #9
Duo is offline Duo  Canada
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Yes thousands, be it an inconceivable amount, as a hobbyist I have spent 12 hours a day many days of my life working on amplifiers because I have so much enthusiasm in the technology. I also design and build my own amplifiers for personal use and to sell to friends.

I'm sorry I was in a bad mood yesterday and kinda vented there. But my point was as maylar says now, there's no reason why a simple upbringing in the very basics wouldn't enable one to diagnose most problems with consumer audio equipment.

maylar: Yes I respect your point, just on your first post, I was worried that you might put David off of this interesting realm of electronics entirely. It really isn't difficult to work on amplifiers and so I figure everyone should have a chance to learn. So, sorry for my distasteful comment, I just wanted to make sure David wasn't put off.
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Old 23rd December 2004, 09:21 PM   #10
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Default learning

Good Link

http://www.bcae1.com/



Jeff
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