Hello, Can someone help please? I have a constant low pitch sound on my Kenwood KA-6004. This sound increases/decreases as I turn the volume up/down. This happens even if disconnect all inputs (no AUX, Tuner, Phono etc... are connected to the amp). This low pitch sound is also heard through my headphones (with both speakers A and B buttons switched off).
If I switch the "Normal/Separate" button at the back of the amp 'Separate' the noise cannot be heard.
My expertise is very limited and I am hoping someone can give me some pointers on a few easy/initial tests I could run before I take my amplifier to the repair shop.
Cheers,
Marc
If I switch the "Normal/Separate" button at the back of the amp 'Separate' the noise cannot be heard.
My expertise is very limited and I am hoping someone can give me some pointers on a few easy/initial tests I could run before I take my amplifier to the repair shop.
Cheers,
Marc
Spray the Normal / Separate switch with contact cleaner...
Do all the rest as well, if the set is old.
Before that, give the insides a good clean. As in soft brush for dirt, and blower.
Check for bulging caps and loose joints in the pre amp section.
Corroded ground to chassis can also cause this.
And also check your input cables, broken shields have been known for this to happen.
Do all the rest as well, if the set is old.
Before that, give the insides a good clean. As in soft brush for dirt, and blower.
Check for bulging caps and loose joints in the pre amp section.
Corroded ground to chassis can also cause this.
And also check your input cables, broken shields have been known for this to happen.
Leaving the input jacks UNloaded without a source WILL allow hum to happen.
Those inputs are then wide open to all sorts of interference.
In testing, inputs are shorted with shorting plugs to eliminate any noise issues during testing.
If the amp hums with a source connected and selected, bad grounding is going on.... bad cables, etc.
OR.... an issue internally with the amp.
Those inputs are then wide open to all sorts of interference.
In testing, inputs are shorted with shorting plugs to eliminate any noise issues during testing.
If the amp hums with a source connected and selected, bad grounding is going on.... bad cables, etc.
OR.... an issue internally with the amp.
As wiseoldtech says:
This is a real oldie 🙂 So you need to pick one line level input and select that one with the input selector. Fit shorting plugs to the sockets of that one input and make sure you have nothing else connected apart from speakers or headphones. There must be no other connections to the amp.
If it hums or buzzes in that state then the amp has a problem.
Assuming it does still hum then you really need proper diagnosis using an oscilloscope but I would say that this one part (circled) would be worth replacing. This is the main reservoir cap for the single ended supply to the preamp stages. I don't normally recommend random component swaps without test and measurement but if you have limited resources for testing then it would be worth trying.
Beyond that... test and measurements.
This is a real oldie 🙂 So you need to pick one line level input and select that one with the input selector. Fit shorting plugs to the sockets of that one input and make sure you have nothing else connected apart from speakers or headphones. There must be no other connections to the amp.
If it hums or buzzes in that state then the amp has a problem.
Assuming it does still hum then you really need proper diagnosis using an oscilloscope but I would say that this one part (circled) would be worth replacing. This is the main reservoir cap for the single ended supply to the preamp stages. I don't normally recommend random component swaps without test and measurement but if you have limited resources for testing then it would be worth trying.
Beyond that... test and measurements.
Thanks everyone. I will try your recommendations. Beyond that, if the problem persists, the next step is to take it to the repair shop.