Hi, My C26 has humming both Channel, but strange thing is that when I turn the Loudness control knob to Max position the humming is decreasing and no humming at Max position. All original and no re-Cap job so far, any idea what causing the humming?
Usually hum is from leaky electrolytic capacitors, so you might as well go ahead
and replace those two cans in the power supply.
and replace those two cans in the power supply.
I would start by inspecting the loudness knob for any contact issues across the knob's range. No hum at Max position tells me there is a contact issue in the potentiometer or switch that the knob is turning.
Hum at midway and not at max can also be an unshielded or poorly routed wire from the pot wiper.
But it wasn't that way from the factory. Has somebody been working inside?
But it wasn't that way from the factory. Has somebody been working inside?
Thanks for the advise. When the Loudness control is in flat position the humming is at max, real loud .,,, as I turn the Loudness knob towards to Max position the humming is decreasing accordingly and finally no humming at Max position of Loudness knob!!!! I am sure that unit is in stock, used to belong to my family member and spent most of its life in storage. Is it can capacitor needs to be replace still? or something much worse?
Hi, I would start by cleaning the loudness knob with contact cleaner. If that doesn’t fix the issue then try to find the source of the hum. Since you can reproduce (and quiet) the hum consistently with the loudness knob I am betting that is the likely culprit. I would not replace components like the capacitors until you have verified they are out of specification or faulty.
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Is there a turntable connected to the phono inputs? If so, can you see if the hum continues after disconnecting the turntable?
Also, disconnect all of the inputs, leaving connected only the outputs, and try the loudness control again.
Is the hum still there? What does the balance control do now?
Is the hum still there? What does the balance control do now?
Disconnecting inputs leaves them Wide Open, and prone to radiated hum.
Best way is to select a source input and use shorting plugs to load them down.
People disconnect their turntables from the inputs, and wonder why the amp's phono input now hums like crazy.
They don't understand, and need to learn the basics.
I don't use turntable and no connection to phono input, only use CD in aux input no tape , no turner input ,,,, although let me try to disconnect the aux input and see if humming continues.
also The balance control has no effect on humming, although let me disconnect the Aux input and see how it is...
At the extreme "off" position of the balance control, the line stage input is grounded.
So if there is still hum in the output, the problem is either noise in the ground bus,
or else somewhere after the balance control.
So if there is still hum in the output, the problem is either noise in the ground bus,
or else somewhere after the balance control.
Hi,
I'm not familiar with this loudness knob. Can you tell me is there a pot or switch? Are you able to see if there is an access hole for contact cleaning with a cleaner such as deoxit?
I'm not familiar with this loudness knob. Can you tell me is there a pot or switch? Are you able to see if there is an access hole for contact cleaning with a cleaner such as deoxit?
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Thank you for Reply, I cleaned and lubricated all the switch check all the wire connection, nothing is shorting, all the cold soldering joint is good, the shield for #1,#2 wire from loudness control and balance is good, just can not figure out what causing the hum,,,,, filter cap is the problem? if it is the leaky cap,, it will hum all the time,,, can it be no humming at Max Loudness position??
I was afraid that cleaning wouldn’t be the solution. I found this 2013 post on audiokarma that might be helpful: https://audiokarma.org/forums/index.php?threads/c26-with-humming-and-mc2505-with-noise.513287/
It looks like the solution was replacing the "can capacitors" I believe those are the same capacitors rayma pointed out early on.
Yes, the 120Hz hum will vary in level with the settings of the various controls and switches.
A unit this old would be expected to require some power supply service, as well as a general
cleaning up. Be sure that the replacement parts properly fit the board, some will not.
A unit this old would be expected to require some power supply service, as well as a general
cleaning up. Be sure that the replacement parts properly fit the board, some will not.