Pioneer SC-LX73 humming / fan?

Discussion in 'AV Receivers & Amplifiers' started by Spatula22, Feb 19, 2013.

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  1. Spatula22

    Spatula22
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    Hi!
    I have just brought a used Pioneer SC-LX73 and have had it running for a few days now. The other night I noticed a humming sound which after turning off all other equipment I have narrowed down to be coming from the receiver itself. It sounds a bit like a computer fan, it runs for about 20-30 seconds, then stops for 5-10 seconds then starts again. It doesn't start as soon as I turn it on, only after about 10 minutes of the receiver being used does it start. It is pretty loud - I first noticed it whilst watching tv at average volume sitting about 10 feet away.
    Is this type of noise usual (or usual to be that loud) for receiver like this? My old Denon 2310 didn't make this sort of sound (or at least wasn't noticeable).

    As it takes a while before it starts my first thought is it is due to heat. The tv rack it sits in is totally open front and back, there are 5cm between the top of the receiver and the shelf above, 20cm to the right but the front half of the left side is touching the leg of the stand. The top of the receiver is warm to touch after around 15-20 minutes.

    I understand it is incredibly difficult for someone to diagnose a 'humming' just from a description but I would appreciate any thoughts on whether this sounds normal or a possible fault as the seeds of panic are quickly starting to grow!
    Thanks!
     
  2. Spatula22

    Spatula22
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    Sorry, I should add that I'm currently using Kef 2005.3 speakers. The Pioneer manual states 'speaker impedance 6-16 ohms'. The Kefs I believe are 8 ohms. I don't fully understand it but from what I've read looking into possible causes, if the speaker impedance is too low it can cause a problem? The kefs are towards the bottom of the bracket but are within Pioneer's stated requirements so hopefully that is not the issue.
     
  3. vidjo

    vidjo
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    There is a mention of a fan in the manual so it's probably that. It would seem that the power supply is quite small - looking at the spec on the max output with all 7 channels running compared to the output with just 2. It's quite likely for a fan to come on at even lower levels.
    Your speakers are fine - no problem being 8 ohms, which is a very common figure.
     
  4. Lesmor

    Lesmor
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    There is a good article on Audioholics about ohm settings in relation to amp performance and temperature
    If I remember correct do a search for a Yamaha Z7 review and it is mentioned there.

    As it is used have you checked what the ohm setting the amp has been set at as it may be user configurable and perhaps the previous owner has changed it, I also believe the Pioneer default might be 6ohms, if you have the manual it should tell you where to find this

    Note of caution I do not know the consequences of running an amp at 6ohms (which I suspect your Pioneer default is) into 8 ohm speakers, but I am sure someone here does, also the Pioneer can probably be configured to 8ohms if needed

    Failing that you could reset the amp to factory settings and check the amp default ohm setting and see if it matches your speakers

    When I had my Yamaha Z7 I was concerned because the amp default was
    8 ohms with an option to change to 6ohms and my speakers were 4 ohms and I wondered if I should change it to 6ohm for a closer match.
    After reading the Audioholics article my mind was put at rest and I was happy to run the amp at default 8ohms, so higher to lower was not an issue for me but I can appreciate your concern.
    Hope this helps and does not confuse
     
  5. Spatula22

    Spatula22
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    Thank you both for your replies!

    vidjo - thanks, yeah it certainly sounds like a fan going. I was concerned that as it doesn't come on instantly like say a pc fan does, then it was kicking in when overheated. It could equally be coming in when it reaches a certain temperature to stop it from over actually heating! Thank you for looking at the spec and your comments regarding the power supply and fans at low volumes, and also your re-assurance on the speakers.

    Lesmor - thanks for the heads up about the Audioholics article, I'll definitely check it out. I haven't checked on the amp itself for the ohm setting - I'm hoping to be able have a proper play with the receiver tomorrow evening! I have searched the pdf maunual for the terms ohm and impedance and nothing regarding settings came up other than "if you have connected speakers with a 6ohm impedance, change the impedance setting before turning on the power". That has me scratching my head a bit, there must be a setting then, but before you turn the power on?? It handily says nothing more on the matter!
    Ah right, cheers. Yeah that would make sense to me too, set it closer to the value of the speakers. I shall head to the Audioholics site now :)

    Thanks again for your help, much appreciated! :)
     
  6. Lesmor

    Lesmor
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    Hi Again
    Yes its confusing more so with what you have found in the manual, but by the comment the amp default might be 8ohm so your good, the problem being that you don't know what the previous owner had it set at or indeed if it has ever been changed.
    Many amps now have fans to control temperature and they will cut in even at default settings

    Taken from the Audioholics article in case you miss it, caveat I do not take responsibility for the accuracy of the article but it set my mind at rest

    Choosing the Speaker Impedance
    I tested the RX-Z7 in the "8 ohm or more" and "6 ohm" settings and as you will see in my lab tests, power was drastically reduced in the "6 ohm" setting. In NO circumstance do I ever recommend using this setting regardless of your loudspeaker impedance. This switch is put there for one purpose only – to pass UL heat dissipation requirements of driving low impedance loads. All it does is limit the output voltage to the amplifiers so that they clip at lower power and thus under their test condition, the receiver generates less heat.
     
  7. Spatula22

    Spatula22
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    Hi again!
    That's true, if it warns to change it to six, then it logically it won't be set at 6 ohms by default. However, and forgive me if I'm repeating things, the Pioneer website states the ''impedance at output level = 6 ohm"
    SC-LX73 Pioneer - Amplifier, AV Receiver - Audio - Video
    it says 6 ohm again under the 'power output' section. It may just be stating the minimum as it clearly says on the back of the unit 6-16. I have done many google searches and cannot find anywhere an option to change the setting. I will contact Pioneer and ask them for peace of mind.
    I will perform a 'reset to factory defaults' to make sure the previous owners settings are removed and to start from fresh.
    Thanks for posting the extract from Audioholics, it is an interesting read. hehe cheers, understood.
    Cheers again mate!
     
  8. vidjo

    vidjo
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    Pioneer have not made any adjustable setting to alter the speaker impedance matching. Yamaha have for some years fitted a switch, although marked as impedance, it doesn't actually change that, but as indicated by the Audioholics article, it reduces the voltages that the amplifier operates with. This is basically to protect the output stages from passing too much current and overheating. Their article is wrong to suggest -leave it on high with 6 ohm speakers - as that could cause serious damage to the amplifier. The Pioneer is safe operating into any impedance from 6 - 16 ohms. With all the electronics crammed into the box they have to make sure it's reasonably protected against overheating, and that's why they have fitted a fan. It shouldn't really be audible normally, but as with computer fans, they have small bearings and will get noisier as time passes. I would expect that after say 2 years from new a clean and lubricate should do the job to reduce the noise.
     
  9. larkone

    larkone
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    The noise could just be from too much dust on the fan blades. Cheap to check and rectify before you look to replacing the fan. If that doesn't fix I would replace with a quiet PC fan rather than trying to service the fan as it is likely to get noisy again soon. They are such low cost parts they are not worth fixing.
     
  10. Spatula22

    Spatula22
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    Hi, thank you for the additional replies.
    Thanks for the comment regarding the Pioneer being safe within its stated impedance range and without settings.

    Regarding the fan, would you expect it to run continuously once it kicks in? It runs for about 20-30 seconds then stops for 5-10 seconds before starting again. In way that makes it more noticeable, the whole not noticing a noise until it stops.
    If needed, a new, maybe quieter, fan sounds like a relatively cheap and easy way to solve the issue.
    Cheers!
     
  11. vidjo

    vidjo
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    Unless you can find out exactly what speed the fan runs and whether it will match the circuit it may make it difficult to replace with a different fan. I expect the original would have been very quiet when new. It possibly has it's own plug to suit the amplifier connection, or may even be soldered in. It should be available via a Pioneer dealer who could order it for you if you want to replace it. The switching will be controlled by an electronic sensor circuit that will usually adjust the speed of the fan - going faster as temperatures rise. Short on times suggest the control is precise and with a small temperature change between on and off.
     

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