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Hi, I'm having problems with my car amp Mcintosh MC440M, installed with 5 channel, 2x100/2x100 and subwoofer.
A signal is cut after a few minutes, the light power guard is "on" constantly , moving the radio volume knob is turned out again, sometimes happens 1 hour to the problem appears again. In the past normally the power guard light is activated only in the volume peaks .... Check loose connections or some but all is well, I also changed the position of the rca inputs to rule whether the problem was the radio outputs, but failure always appears in the same amplifier output 1, the problem occurs even at low volume ....... any advice?

Best regards, Pablo.
 

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Hi, I'm having problems with my car amp Mcintosh MC440M, installed with 5 channel, 2x100/2x100 and subwoofer.
A signal is cut after a few minutes, the light power guard is "on" constantly , moving the radio volume knob is turned out again, sometimes happens 1 hour to the problem appears again. In the past normally the power guard light is activated only in the volume peaks .... Check loose connections or some but all is well, I also changed the position of the rca inputs to rule whether the problem was the radio outputs, but failure always appears in the same amplifier output 1, the problem occurs even at low volume ....... any advice?

Best regards, Pablo.
-What make/model is the car?
-What is the output capacity of the alternator?
-What is the gauge of the power wire, what else is using it, where is the amp grounded and what is the gauge of the ground wire? If the ground wire doesn't go straight to the battery - post, did you add a heavier wire from the battery - to the body? That's critical- the car may not have a heavy enough ground wire to support the additional current needed by the amplifier.


-Where is the amp mounted? If it's upside-down under the package shelf, move it so the top is up and the bottom is down.
-If the amp is in the trunk, do you fill the trunk with so much stuff that it's keeping the amp from cooling properly?
-How many speakers are connected to each channel?
-What kinds of music are you playing and how loud?
-How did you set the amplifier's input level controls and what is the output of the head unit? Exceeding the usable input level eliminates headroom and causes clipping, which will make the amp shut down, IIRC.
-What are the tone control settings? If the bass is too high, it can cause the same problems as high input levels.
-What are the crossover settings? If the smaller speakers are getting too much bass, the amp channels are working too hard and that will cause it to overheat.

Inadequate power wire gauge will kill your amplifier, alternator and speakers because the amplifier will never see the necessary voltage needed to develop full power. Amplifiers don't usually develop full power at 12VDC, they need the full 14.4VDC. Some do, but they don't do very well when you need a lot of headroom at high power levels.

List everything in the system, including wire gauge, power wire connections, speaker make/model, etc. You can post photos of the settings and other details.
 

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Discussion Starter #3
-What make/model is the car?
-What is the output capacity of the alternator?
-What is the gauge of the power wire, what else is using it, where is the amp grounded and what is the gauge of the ground wire? If the ground wire doesn't go straight to the battery - post, did you add a heavier wire from the battery - to the body? That's critical- the car may not have a heavy enough ground wire to support the additional current needed by the amplifier.


-Where is the amp mounted? If it's upside-down under the package shelf, move it so the top is up and the bottom is down.
-If the amp is in the trunk, do you fill the trunk with so much stuff that it's keeping the amp from cooling properly?
-How many speakers are connected to each channel?
-What kinds of music are you playing and how loud?
-How did you set the amplifier's input level controls and what is the output of the head unit? Exceeding the usable input level eliminates headroom and causes clipping, which will make the amp shut down, IIRC.
-What are the tone control settings? If the bass is too high, it can cause the same problems as high input levels.
-What are the crossover settings? If the smaller speakers are getting too much bass, the amp channels are working too hard and that will cause it to overheat.

Inadequate power wire gauge will kill your amplifier, alternator and speakers because the amplifier will never see the necessary voltage needed to develop full power. Amplifiers don't usually develop full power at 12VDC, they need the full 14.4VDC. Some do, but they don't do very well when you need a lot of headroom at high power levels.

List everything in the system, including wire gauge, power wire connections, speaker make/model, etc. You can post photos of the settings and other details.
ok, what is the minimun gauge wire for power and ground in my amplifier??
 

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And you still haven't posted anything about the car- is it a compact, mid-size, full-size, truck with a ton of accessories? It all matters and if you experience this while idling for long periods or when the lights, wipers and other accessories are in use, you need to look at the charging system. A good indicator is your headlights unless they're LED- if you see them dim when deep bass notes hit, you need more from your charging system. A stiffening cap isn't going to do it, either.
 

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And you still haven't posted anything about the car- is it a compact, mid-size, full-size, truck with a ton of accessories? It all matters and if you experience this while idling for long periods or when the lights, wipers and other accessories are in use, you need to look at the charging system. A good indicator is your headlights unless they're LED- if you see them dim when deep bass notes hit, you need more from your charging system. A stiffening cap isn't going to do it, either.
Sorry, is a vw classic superbeetle 1303 1973, 55 amps alternator. the amplifier normally worked about a year fine, now with the same connections without modifications began to fail intermittently ...... sometimes occurs at 2 minutes, sometimes two hours, all without giving much power .. ... with the engine on or off happens the same ... the car has charging system very well, and the battery is fine too ..... the car does not have additional accessories that consume power only thing weird is that the power light guard is active even at low volume ... only the peaks before .....

Radio mcintosh, crossovers mcintosh, 2x100 morel speakers with tweeters front, 2x100 mcintosh speakers with tweeter rear, 1 subwoofer mid size.
 

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Sorry, is a vw classic superbeetle 1303 1973, 55 amps alternator. the amplifier normally worked about a year fine, now with the same connections without modifications began to fail intermittently ...... sometimes occurs at 2 minutes, sometimes two hours, all without giving much power .. ... with the engine on or off happens the same ... the car has charging system very well, and the battery is fine too ..... the car does not have additional accessories that consume power only thing weird is that the power light guard is active even at low volume ... only the peaks before .....

Radio mcintosh, crossovers mcintosh, 2x100 morel speakers with tweeters front, 2x100 mcintosh speakers with tweeter rear, 1 subwoofer mid size.
Try cleaning the battery terminals. Make sure every connection in the power circuit is clean and tight, check the electrolyte level in the battery and check the fuse holder for the amp- I have seen the plastic deform and cause the fuse to become loose, making bad contact.

Your battery isn't very large and if you have used the stereo for long periods with the engine not running, I can guarantee that the electrolyte level is low unless it's a totally sealed design. In that case, I would bet that it won't be long before your starter will begin to crank slower than usual and eventually, it will have a hard time doing that.

You can change a couple of settings as a test- decrease the level of the subwoofer- if it improves, it could be a problem with the speaker or that channel. If that doesn't help, do the same for the other speakers and see if it changes anything.

If you have a multi-meter, you can test the current draw of the amp and the integrity of the power wires- if the power wires have any crimp-on terminals (ring, butt-splice, etc) and they weren't soldered, I would recommend making new connections. Corrosion causes this kind of problem on un-soldered connections.

For this test, you can leave the key and the stereo power off-
1) Measure the DC voltage at the battery posts.
2) Measure the DC voltage on the power wire's terminals. If you see any difference, clean the terminals.
3) Measure the DC voltage at the next connection point and clean any connections that are causing voltage drop.
4) Measure the voltage at the amplifier's red and black terminals. If you see less voltage than what you measured on the battery terminals, clean the terminals and wire ends (especially if you didn't use spade terminals).
 
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