Kenwood KA-4006 volume control issue

[DrumminDaddy]

Tinkering with this dainty little amplifier that seemingly works well in every respect except the volume will not turn completely off. Regardless of the position of tone section or muting switch, I get some play at zero. The muting switch greatly diminishes it, but it never goes quiet.

I’m at a loss to figure out the issue. Any suggestions on where to troubleshoot would be greatly appreciated.

Regards,

DD

 

[Grenadeslio]

Tinkering with this dainty little amplifier that seemingly works well in every respect except the volume will not turn completely off. Regardless of the position of tone section or muting switch, I get some play at zero. The muting switch greatly diminishes it, but it never goes quiet.

I’m at a loss to figure out the issue. Any suggestions on where to troubleshoot would be greatly appreciated.

Regards,

DD

I have 3 of these little amps, really like the warm presentation and they punch way above their weight.

So after reading your post I decided to see if the one in my bedroom system acted the same. Now I have mine playing through Klipsch Heresys with the only source a Sony ES disc player. Keep in mind CD players typically have relatively high outputs compared with what these little gems would have encountered in their time. Add to that the sensitive nature of the Klipsch speakers and my setup should be a prime candidate for similar results.

Well with the volume all the way down and my ear against the midrange horn I could "just barely" discern Crosby, Stills, Nash & Young from the left speaker. The right speaker had a slight hiss but no music.

 

[DrumminDaddy]

I have mine playing with my iPhone as a source. I considered that the input may be driving it too hard and turned the phone down considerably. It lowers it some. I can hear it clearly without putting my head near the speakers.

 

[hopjohn]

DD, check / reflow the the ground connection of the volume pot. It's a typical problem when there's a less than good connection there. Hope it helps.

 

[VYNULADIKT]

I've had dirty pots do that due to lack of good contact on the ground wiper. It can't fully attenuate the signal.

 

[DrumminDaddy]

DD, check / reflow the the ground connection of the volume pot. It's a typical problem when there's a less than good connection there. Hope it helps.

I've had dirty pots do that due to lack of good contact on the ground wiper. It can't fully attenuate the signal.

Good tips, many thanks.
I’ll look into that and see what I can find.

 

[DrumminDaddy]

Ground lugs of left/right pot read a dead short to chassis.
Wiper lug at lowest setting reads considerably higher.

 

[hopjohn]

Ensure you have good chassis ground to the body of the pot.

Connect some test leads from ground to each center tap (left and right). Play something with the pot at minimum. If you're still getting sound at the same level as before then you can eliminate the pot as the problem. If the sound goes away you'll need to be sure the pot is clean or the connections to the pot are good otherwise the pot is likely bad.

 

[DrumminDaddy]

Ground of pot body checks ok. Grounded both center lugs and she quieted right down.

 

[Artie]

I've actually seen a good shot of Deoxit fix this kind of problem. Worth a shot.

 

[DrumminDaddy]

I've actually seen a good shot of Deoxit fix this kind of problem. Worth a shot.

That was my first action. It’s looking like the pot has seen better days. Even the attenuator switch doesn’t pull it all the way down. I’m just going to relegate this one to shop duty for now. Not worth much more effort to me at this time.

As a side note, I do see a gent at auction selling brand new stereo pots with loudness tapers. A bit salty, though.

 

[hopjohn]

Here's some 4006 parts. No affiliation...
https://www.etsy.com/listing/687813...+ka&ref=sr_gallery-1-2&organic_search_click=1