Hi I have nakamichi sr-4a.
I bought it used. Don't know history behind it.
It started to hum. 60hz humming noise from speakers.
It does it when it warms up. If I don't use it for few days it does not hum initially but then starts making noise. (Noise comes fron speakers not receiver )
It hums always. Does not matter which input source is cosen.
Humming dissappear when I push "mute "button. Which basically halves volume output. Humming noise does not depend on volume level.
I've read in other threads that it may be large capacitors.
Another thing
In my apartment electric wiring is weird. Not done right.
Voltage drops.. especially when everyone is using AC.
So some equipment turns off during these voltage drops.
Other receivers don't hum when plugged into the sam outlet.
How can bad wiring constitute to humming?
Or is it the problem in receiver. I'll try this receiver at my friends place tomorrow.
It's just no other receiver hums ..only nakamichi. All receivers power off during voltage drops. But none hum.
I tried tightening board bolts inside receiver
Grounding ground star nut in the back of the receiver.
I hear change in humming when moving power cable in various positions
I bought it used. Don't know history behind it.
It started to hum. 60hz humming noise from speakers.
It does it when it warms up. If I don't use it for few days it does not hum initially but then starts making noise. (Noise comes fron speakers not receiver )
It hums always. Does not matter which input source is cosen.
Humming dissappear when I push "mute "button. Which basically halves volume output. Humming noise does not depend on volume level.
I've read in other threads that it may be large capacitors.
Another thing
In my apartment electric wiring is weird. Not done right.
Voltage drops.. especially when everyone is using AC.
So some equipment turns off during these voltage drops.
Other receivers don't hum when plugged into the sam outlet.
How can bad wiring constitute to humming?
Or is it the problem in receiver. I'll try this receiver at my friends place tomorrow.
It's just no other receiver hums ..only nakamichi. All receivers power off during voltage drops. But none hum.
I tried tightening board bolts inside receiver
Grounding ground star nut in the back of the receiver.
I hear change in humming when moving power cable in various positions
If the hum goes away when the muting switch is activated, this means the power amplifier section is good. All remaining is the
volume/balance/tone controls. See if the hum is affected when turning the tone controls off.
Thanks I'll check how tight the bolts are. Clean them
.I just plugged receiver in at a different apartment. No humming.
Just curious what could cause this.
Again there is fluctuating voltage in my apartment. But all receivers I used here don't hum. They dopower off if vpower outlet voltage drops too much. Any way to measure ac voltage frequency without osciloscope?
It definitely drops from 115v to say 90v just looking at the lights dim
I am living in brooklyn usa for those who wonder where in the world are there such power outlets.
.I just plugged receiver in at a different apartment. No humming.
Just curious what could cause this.
Again there is fluctuating voltage in my apartment. But all receivers I used here don't hum. They dopower off if vpower outlet voltage drops too much. Any way to measure ac voltage frequency without osciloscope?
It definitely drops from 115v to say 90v just looking at the lights dim
I am living in brooklyn usa for those who wonder where in the world are there such power outlets.
Hard to say, some equipment is more sensitive to certain problems.
Don't worry about the line frequency, that can't be off. Maybe some outlets in your apt are better than others.
Experiment with an extension cord.
What I guess may be happening is that the filter caps in the preamp power supply have seen better days and it doesn't take much for the regulators to drop out.
You can check line voltage using a (somewhat trustworthy) multimeter. Adequate safety provisions are likely to mean that it costs more than 5 bucks (though I have used Mastech cheapies and nothing bad happened), or at least did so when new.
This electrical problem should definitely be looked at. Given the situation in NYC, I suspect that the wiring is a few decades older than it should be and as such may be plain undersized (do other apartments in the same building share this problem?), but there may be corroded screw-in fuses / fuseholders as well or even a bad connection somewhere, which potentially is a fire waiting to happen. If you don't find anything suspicious yourself (it'll be warm), consult an electrician.
You can check line voltage using a (somewhat trustworthy) multimeter. Adequate safety provisions are likely to mean that it costs more than 5 bucks (though I have used Mastech cheapies and nothing bad happened), or at least did so when new.
This electrical problem should definitely be looked at. Given the situation in NYC, I suspect that the wiring is a few decades older than it should be and as such may be plain undersized (do other apartments in the same building share this problem?), but there may be corroded screw-in fuses / fuseholders as well or even a bad connection somewhere, which potentially is a fire waiting to happen. If you don't find anything suspicious yourself (it'll be warm), consult an electrician.
> Any way to measure ac voltage frequency without osciloscope? It definitely drops from 115v to say 90v just looking at the lights dim
Frequency in Brooklyn will BE 59.9Hz-60.1Hz nearly all the time. Brooklyn power is locked to the Grid, thousands of generators, who must all agree on a target frequency and use very slight change of freq to adjust their output. Your frequency is fine.
As said, a simple volt meter will tell Voltage. PLEASE do not get shocked sticking bare probes in a live outlet!! Safe meters:
DROK Flat Plug AC 80-300V
Yeeco Wall Flat US Plug 80-300V
P3 P4400 Kill A Watt
That last one, KillAWatt, will read Frequency. And Amps and KWH and PF, none of which you need.
Unless you have a serious fault in supply, 115v to 90v seems unlikely. 1% change of voltage makes 3.5% change of incandescent lamp light output. Or at 90V you will get 43% of nominal light, very dark!
Voltage Variation Effects
Are your computers and clocks re-booting? Does your air conditioner refuse to start?
I'm thinking you mean 22% change of light (very visible), which is about 93% of voltage, or 107V of nominal 115V. Or since much of the US is nominal 120V, 112V dips.
I have a too-long power line to my shack in the woods. I have 125V no-load, 117V much of the day, and 108V when many major appliances run at once (laundry). The lights do sag when the well-pump starts. It is not a problem.
Frequency in Brooklyn will BE 59.9Hz-60.1Hz nearly all the time. Brooklyn power is locked to the Grid, thousands of generators, who must all agree on a target frequency and use very slight change of freq to adjust their output. Your frequency is fine.
As said, a simple volt meter will tell Voltage. PLEASE do not get shocked sticking bare probes in a live outlet!! Safe meters:
DROK Flat Plug AC 80-300V
Yeeco Wall Flat US Plug 80-300V
P3 P4400 Kill A Watt
That last one, KillAWatt, will read Frequency. And Amps and KWH and PF, none of which you need.
Unless you have a serious fault in supply, 115v to 90v seems unlikely. 1% change of voltage makes 3.5% change of incandescent lamp light output. Or at 90V you will get 43% of nominal light, very dark!
Voltage Variation Effects
Are your computers and clocks re-booting? Does your air conditioner refuse to start?
I'm thinking you mean 22% change of light (very visible), which is about 93% of voltage, or 107V of nominal 115V. Or since much of the US is nominal 120V, 112V dips.
I have a too-long power line to my shack in the woods. I have 125V no-load, 117V much of the day, and 108V when many major appliances run at once (laundry). The lights do sag when the well-pump starts. It is not a problem.
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Earthing/ground loops and associated humming is rather complex/beyond me.
Things to keep in mind are that the mains AC is rectified/converted to dc
however there is some residual AC after conversion that's superimposed on
the dc (AC ripple at twice mains frequency/120Hz?, 1Vpeak to peak would be
large, more like a few hundred mV).
Generally, the power amp stage takes this rectified dc with AC ripple without
further treatment, except for the main filter caps, and works ok. If the main
filter caps don't hold their charge, the ripple may be greater, to the point
where it is noticable in the power amp stage. So main filter caps are a candidate
as are the rectifier diodes, though less likely.
The preamp stage normally uses a voltage regulator transistors/chips which greatly
reduces the ripple. Certainly if the transistors that make up this regulator are tired
then the ripple can be introduced into the preamp stage.
Ideally an oscilloscope should be used to track this down. Next would be a true RMS
voltmeter. Cheap voltmeters will interpret the AC ripple superimposed on dc as significant
AC, eg, 1Vp-p ripple on 50Vdc could be displayed as 90(or so) Vac. Reversing the polarity
of the probes(yes, ac) will then give 0Vac on these cheap meters, I have 2.
Suggest you use athe Nak as a seperate, ie connect another preamp (or even ipod at very
low vol) to the MAIN-IN, if hum present indicates problem in power amp, so start by
replacing main filter caps and maybe diode. The other test is to use the Nak preamp
(PRE-OUT) into another power amp. If hum present then check out voltage regulation.
There are about 27 other causes for hum...
Things to keep in mind are that the mains AC is rectified/converted to dc
however there is some residual AC after conversion that's superimposed on
the dc (AC ripple at twice mains frequency/120Hz?, 1Vpeak to peak would be
large, more like a few hundred mV).
Generally, the power amp stage takes this rectified dc with AC ripple without
further treatment, except for the main filter caps, and works ok. If the main
filter caps don't hold their charge, the ripple may be greater, to the point
where it is noticable in the power amp stage. So main filter caps are a candidate
as are the rectifier diodes, though less likely.
The preamp stage normally uses a voltage regulator transistors/chips which greatly
reduces the ripple. Certainly if the transistors that make up this regulator are tired
then the ripple can be introduced into the preamp stage.
Ideally an oscilloscope should be used to track this down. Next would be a true RMS
voltmeter. Cheap voltmeters will interpret the AC ripple superimposed on dc as significant
AC, eg, 1Vp-p ripple on 50Vdc could be displayed as 90(or so) Vac. Reversing the polarity
of the probes(yes, ac) will then give 0Vac on these cheap meters, I have 2.
Suggest you use athe Nak as a seperate, ie connect another preamp (or even ipod at very
low vol) to the MAIN-IN, if hum present indicates problem in power amp, so start by
replacing main filter caps and maybe diode. The other test is to use the Nak preamp
(PRE-OUT) into another power amp. If hum present then check out voltage regulation.
There are about 27 other causes for hum...
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