A/V Receiver Weirdness - No Audio Plus Ominous Humming

ElJeffe

I have begun intermittently having a problem with my A/V receiver. At times, the audio will go out and be replaced by a feedback-y humming noise that typically ramps up in volume to extremely high levels (though the noise can be adjusted down with the volume knob). The problem will persist across all inputs (which are a mix of HDMI, optical, and composite stereo). When this occurs, the only way to solve the issue is to just turn the receiver off for ten minutes or so, and when it turns back on, everything is normal. (Once, though, it took several hours for the problem to resolve itself.)

The receiver is a Marantz SR5003, about five years old, and the problem only began about a year ago. It only occurs once every few months or so, so it's not a huge problem in itself, and other than that the receiver works perfectly. If this is as bad as the problem gets, I'd rather just deal, because I don't want to drop a couple hundred bucks to fix what is really a minor annoyance. But I don't want to ignore what is a fairly cheap fix now if it's a precursor to my receiver exploding, because it's a pretty swell receiver.

I've hunted for info on this problem for this receiver on various AV sites, and haven't found anything that sounds similar. I'm not expecting an actual fix, just hopefully some idea of what the magnitude of this problem might be.

Dibbit

Although I almost have the same reciever, I'm afraid I know only the broad strokes about how it works inside. The only "advice" I can give you is that some Marantz recievers qualify for 5 years of factory warranty, instead of the normal 3. I don't even know if this is true outside of Europe, though.

edit: Seems yours isn't one of them. So... completely useless advice.
Euhm... It must be the DAC? (don't take this suggestion seriously)

Have you tried using stereo direct when it's humming?
It should be called (pure) direct on the remote (2nd button, 2nd row on mine) and it basically switches of almost all extra "filter chips" on the reciever, such as the equalizer, the audessy setting and a bunch of chips that add value to the sound but that can break.
If that doesn't mute the humm, you know it's a problem in either the inputs, the converter or the amp, as it should only be using those circuits.
Unfortunately, those are also the key parts of your reciever.

Donovan Puppyfucker

It sounds like there's an overheating problem with the first stage of the amplification circuitry.

ElJeffe

I've tried putting it on Pure Direct before, and it didn't solve the problem. I will assume it's unlikely that every input goes weird at the same time, which leaves the converter or amp, and the amp seems a likely culprit.

Would trying to physically isolate the receiver a bit more so it has more airflow around it help at all? Should I open it up and see if it's getting choked with dust, maybe vacuum or blow it out with some compressed air?

Dibbit

ElJeffe wrote: »

I've tried putting it on Pure Direct before, and it didn't solve the problem. I will assume it's unlikely that every input goes weird at the same time, which leaves the converter or amp, and the amp seems a likely culprit.

Would trying to physically isolate the receiver a bit more so it has more airflow around it help at all? Should I open it up and see if it's getting choked with dust, maybe vacuum or blow it out with some compressed air?

It might help, if the amp is overheating, dust might be the cause. My personal experience with recievers is that they get way less dusty then PCs, as they don't have any vents forcing airflow, all the cooling is done via convection.
Having said that: making sure that both the top and bottom are clear sounds like a good idea.
if it's resting on it's feet on a clear surface, that should be plenty of space, BTW.
Be careful if you open a receiver, even if unplugged some parts can hold a charge for quite some time. (pro-tip: don't get electrocuted.)

Rderdall

I'm a Marantz dealer (in Canada) and the SRXXX3 line and SRXXX4s were a bit troublesome. Marantz has fixed the issues from these lines now, but those two years did not produce very durable products. I've yet to come across a unit that produces a hum, but have seen multiple units from those two series that just up and quit. The Marantz receivers have a protection circuit that shuts the unit off and flashes the Standby LED when things go wonky inside. Is the standby light flashing when your audio cuts out?

EDIT: I just dug up the reset code for that amp. If it shuts down, press and hold Surround Mode + Exit + Clear on the front of the receiver for 3 seconds. This will factory reset your amp, so you'll need to re-assign your inputs, but it should get you out of a bind. If you need to do this often, there's not much you'll be able to do on your own to fix this.

In my experience, there have been three things that have caused receivers to quit, or go into protection mode.
1. Overheating
2. Incorrectly installed speakers (wrong polarity sometimes, but more commonly incorrect impedance eg. 2 speakers wired together and connected to one speaker output)
3. The faulty components in the SRXXX3, SRXXX4 lines

If the hum were there all the time, I'd think it was a ground loop issue. If your power cord has three prongs, you can buy a three prong to two prong adapter from most hardware stores for a couple of dollars to test this out. For the price, it's worth a shot.

The next least-expensive option is to send the unit in for repair. If you go here, you can find your nearest service center. Hopefully there's one in your area so you don't need to ship it anywhere. We've sent multiple receivers in for repair from these lines and they usually take 2-3 weeks to come back and cost about $300-$500. Don't forget that with this option, you'll be without a receiver (which often cripples a media room) for the time it's gone. Additionally, most of the receivers that we had repaired came back fixed, then failed again not too long after.

You spent a lot of money on that unit, so you probably aren't thrilled about the possibility of buying a new one, but the new Marantz receivers are awesome. They even have integrated AirPlay capability so you can stream audio/video right from your Apple devices to your a/v system without having to buy an Apple TV or AirPortExpress. I just put together a project proposal for a client that included a Marantz SR5008 and it's priced pretty decently at around $620.

Donovan Puppyfucker

ElJeffe wrote: »

I've tried putting it on Pure Direct before, and it didn't solve the problem. I will assume it's unlikely that every input goes weird at the same time, which leaves the converter or amp, and the amp seems a likely culprit.

Would trying to physically isolate the receiver a bit more so it has more airflow around it help at all? Should I open it up and see if it's getting choked with dust, maybe vacuum or blow it out with some compressed air?

I was thinking more along the lines of perhaps a heatsink on an op-amp or MOSFET has come loose.

ElJeffe

Rderdall wrote: »

I'm a Marantz dealer (in Canada) and the SRXXX3 line and SRXXX4s were a bit troublesome. Marantz has fixed the issues from these lines now, but those two years did not produce very durable products. I've yet to come across a unit that produces a hum, but have seen multiple units from those two series that just up and quit. The Marantz receivers have a protection circuit that shuts the unit off and flashes the Standby LED when things go wonky inside. Is the standby light flashing when your audio cuts out?

EDIT: I just dug up the reset code for that amp. If it shuts down, press and hold Surround Mode + Exit + Clear on the front of the receiver for 3 seconds. This will factory reset your amp, so you'll need to re-assign your inputs, but it should get you out of a bind. If you need to do this often, there's not much you'll be able to do on your own to fix this.

In my experience, there have been three things that have caused receivers to quit, or go into protection mode.
1. Overheating
2. Incorrectly installed speakers (wrong polarity sometimes, but more commonly incorrect impedance eg. 2 speakers wired together and connected to one speaker output)
3. The faulty components in the SRXXX3, SRXXX4 lines

If the hum were there all the time, I'd think it was a ground loop issue. If your power cord has three prongs, you can buy a three prong to two prong adapter from most hardware stores for a couple of dollars to test this out. For the price, it's worth a shot.

The next least-expensive option is to send the unit in for repair. If you go here, you can find your nearest service center. Hopefully there's one in your area so you don't need to ship it anywhere. We've sent multiple receivers in for repair from these lines and they usually take 2-3 weeks to come back and cost about $300-$500. Don't forget that with this option, you'll be without a receiver (which often cripples a media room) for the time it's gone. Additionally, most of the receivers that we had repaired came back fixed, then failed again not too long after.

You spent a lot of money on that unit, so you probably aren't thrilled about the possibility of buying a new one, but the new Marantz receivers are awesome. They even have integrated AirPlay capability so you can stream audio/video right from your Apple devices to your a/v system without having to buy an Apple TV or AirPortExpress. I just put together a project proposal for a client that included a Marantz SR5008 and it's priced pretty decently at around $620.

Thanks for all the advice! It did the flashing-light bit once, but by the time I figured out what had happened and how to do a reset, the problem had fixed itself.

I'm not willing to eat a potentially several-hundred-dollar repair right now, so I'll probably just hope it doesn't die for now.