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Amplifier help
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G_2442



Joined: 28 Dec 2006
Posts: 3

PostPosted: Thu Dec 28, 2006 9:36 pm    Post subject: Amplifier help Reply with quote

Hey everyone I'm having a problem with my amplifier I wondering if you guys can help me out. This is what's going on.

The amp turns on the Led's on the front light up but I get no sound.

Here are some observations I have made -

1. The relay isn't turning on the amp isn't making the click sound it use to make.
2. When the volume is about all the way up I can faintly here music coming from the amp.
3. There is no output coming from the speaker terminals as well as the headphone jack. I checked the output voltage for speaker set A & B and it read 1.4mV for all 4

Also the amp is over 20 years old it is a sears LXI series amp model AM 4023

Any help would be appreciated Shocked
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BBHE



Joined: 08 Feb 2005
Posts: 12

PostPosted: Sat Dec 30, 2006 3:40 pm    Post subject: Reply with quote

Hi,

I've had same problem with a amp, only in the right channel thow.

In my case it where only the fuses and the output transistor.
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Morrowrj



Joined: 14 Apr 2005
Posts: 29
Location: Pittsburgh, PA

PostPosted: Sun Dec 31, 2006 1:15 pm    Post subject: Reply with quote

Did you open the unit up to give it a good inspection? For amplifiers, often you can see or smell the offending part.
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G_2442



Joined: 28 Dec 2006
Posts: 3

PostPosted: Sun Dec 31, 2006 4:26 pm    Post subject: Reply with quote

Yeah I opened it up there doesn't seem to be any damage to the components. I fuses inside look good to.
Can I Relay go bad?
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Morrowrj



Joined: 14 Apr 2005
Posts: 29
Location: Pittsburgh, PA

PostPosted: Mon Jan 01, 2007 2:37 pm    Post subject: Reply with quote

It is possible but very unlikely. To test it you could jumper out the contacts and see if it works, but you have to get the right ones and depending on size it could be tough.
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Guest






PostPosted: Tue Jan 02, 2007 7:29 pm    Post subject: Reply with quote

I've changed capacitors and relay still no luck anyone have any other ideas
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Ivan
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PostPosted: Tue Jan 02, 2007 8:33 pm    Post subject: relay, amp Reply with quote

If the relay is used to disconnect the speakers from the amp during turn-on, it also monitors DC voltage and will not energize if DC voltage from the amp is present. It is used to protect the speakers. It sounds like the amp has blown a transistor (or cap) and DC voltage is present at one side of the relay. If you jumper the relay, you may damage your speakers....Do you know how to test power transistors with a meter, with power off? At high enough volume levels you will hear audio from the transistors on these older models.
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Guest






PostPosted: Tue Jan 02, 2007 8:44 pm    Post subject: Reply with quote

Since I changed the relay the music from the amp has gotten louder and volume meter has gone higher as well. What should I do next
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Guest






PostPosted: Wed Jan 03, 2007 12:14 am    Post subject: Reply with quote

Well I'm definitely hearing music how do I test the transistors?
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Ivan
Guest





PostPosted: Wed Jan 03, 2007 2:48 pm    Post subject: transistors Reply with quote

This may be a bit difficult if you are not that familiar with electronics, but here goes. Transistors have 3 leads, Case, base, and emitter. With power off, power cord unplugged, give it a few minutes or longer for any caps to discharge. With an ohm meter, check the leads in any order for shorts. These power transistors are usually mounted on a heatsink and at that time, probably plugged into a socket. Hopefully the pins are accessible. the Case lead is the case of the transistor if its metal. Usually, one channel of the 2 channel amp will fail, so you can compare the readings from the left and right side. A low resistance or zero ohms indicates a bad transistor. Part numbers are on the transistor case.
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