Hello everyone!
I am having a little trouble with a Marantz SR4002 7.1 reciever. I noticed a light hum at high volume when the DSP is active. This hum is present in digital mode trough all the digital inputs and also in analog mode when Dolby Prologic II or other surround effects are active, so basically whenever the DSP is used to process audio. In analog mode with Source Direct and Pure Direct activated the hum is gone.
Also when the DSP is active the hiss at high volume is much louder then in analog mode with Pure Direct activated. I know that the Pure Direct`s purpose is cleaner signal path, but still, I think that the hissing should not be that loud. There is also some random static noise present in the right channel which comes and goes as it pleases.
The amp has a feature to use the surround back channels for a second pair of speakers which play the same source as the front speakers. The reason I tell you this is because the static on the right channel is present on both A and B even tough B speakers are separately powered.
I know that sometimes hissing and static and humming noise are because of bad capacitors.
If someone could give me a reference as to were to start check for problems it would help me a lot 😀
Note: I can attach a few JPGs from the service manual if it helps
I am having a little trouble with a Marantz SR4002 7.1 reciever. I noticed a light hum at high volume when the DSP is active. This hum is present in digital mode trough all the digital inputs and also in analog mode when Dolby Prologic II or other surround effects are active, so basically whenever the DSP is used to process audio. In analog mode with Source Direct and Pure Direct activated the hum is gone.
Also when the DSP is active the hiss at high volume is much louder then in analog mode with Pure Direct activated. I know that the Pure Direct`s purpose is cleaner signal path, but still, I think that the hissing should not be that loud. There is also some random static noise present in the right channel which comes and goes as it pleases.
The amp has a feature to use the surround back channels for a second pair of speakers which play the same source as the front speakers. The reason I tell you this is because the static on the right channel is present on both A and B even tough B speakers are separately powered.
I know that sometimes hissing and static and humming noise are because of bad capacitors.
If someone could give me a reference as to were to start check for problems it would help me a lot 😀
Note: I can attach a few JPGs from the service manual if it helps
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Need more History .... Possible Noise Source could be ....
Did this just start to happen? Did you add any new equipment? Have any brown-outs or strange AC line conditions occurred recently? A little history would help diagnose the problem.
I did some looking around on the internet regarding hum and buzzing from Marantz receivers and I found this:
Noise problems with Marantz SR7300 - eCoustics.com
It seems from the posts that Marantz can have self generating noise issues. It is true that receivers can generate their own internal digital noise. If your speakers have a high sensitivity than that can exacerbate the problem.
Have you tried disconnecting all inputs and outputs (except speakers) into the receiver and then seeing if the receiver makes the noise?
xsipower
Did this just start to happen? Did you add any new equipment? Have any brown-outs or strange AC line conditions occurred recently? A little history would help diagnose the problem.
I did some looking around on the internet regarding hum and buzzing from Marantz receivers and I found this:
Noise problems with Marantz SR7300 - eCoustics.com
It seems from the posts that Marantz can have self generating noise issues. It is true that receivers can generate their own internal digital noise. If your speakers have a high sensitivity than that can exacerbate the problem.
Have you tried disconnecting all inputs and outputs (except speakers) into the receiver and then seeing if the receiver makes the noise?
xsipower
I bought the receiver used for about 25$ as cosmetically is pretty beat up. It already had this problem.
The receiver itself is dead silent even with volume on maximum. I use my receiver with a pc connected with digital optical cable. The humming is only heard if there is data coming trough the optical input. If there is no data the DSP is shut off and the humming stops and so does the random static noise on the right channel.
In analog mode the humming is only present with the surround effects turned on. In source direct and pure direct it`s dead silent. So I think that the problem might be at the 5V rail which is supplying the DSPs analog part, but it`s just a wild guess.
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The humming it`s not that bad as I only hear it at very high volume. However the static noise on the right channel bothers me a lot.
I think I came across something. The side of the main power amplifier heatsink which has 3 voltage regulators mounted on it is very warm. So warm that it almos heats up half of the heatsink. The amp in idle does not produse that amount of heat. The other side is cool to the touch. The offset voltage for all of the 7 channels is dead on 5mV, so there are no bad bias settings on the amps on that side of the heatskin. Aslo the heatsink is quiet large and I don`t think a good voltage regulator could heat it up that much
Can voltage regulators go bad but still work with increased heat output?
Can voltage regulators go bad but still work with increased heat output?
A crude test for the heat source is to touch the body of the suspect part with your finger (not any of the leads). You should be able to keep it there - if it feels too hot and have to put away then it will be outside the working limits. Power Transistors these days are mostly housed in plastic packages but in the case of a high power amplifier in metal ones there is likely to be a high voltage on the case - so if you have to do that turn the equipment off and allow a little time for the supply caps to discharge.
Voltage regulators will shut down if subjected to currents in excess of their specifications and will get hot if a short circuit has arisen on the output due to some component failure. Tantalum capacitors on regulator outputs have been known to fail. If these are present they will be small coloured beads rather than cylindrical in shape.
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