Akai AM-2350 noise in the bass knob

[greenflash]

Hi guys, my beloved AM-2350 black amp is acting up since a few months. Used to make a kind of soft hiss sound after a while when I turned it on, so I took off the cover and used contactmatic (the closest thing to deoxit down here) and then it seemed to improve.

But the noise was still there, and I noticed than when pushing or touching the bass knob a little the hiss would be (momentarily) gone. So, took off the cover again and dedicated more time to deoxit the bass knob.

Now, back on, it's a little different, when I turn it on, the sound when I touch the bass knob is like that of a "strong wind", but only when I turn it around, and if turn it for a little while then it slowly goes away.

Didn't try the amp for much longer yet but, is there any other (simple) thing you can think of that could be causing the problem? Thanks as usual!

 

[Oldsansui441]

Hi, l have a 2650, l like this series also. I would start by cleaning all pots/switches again with deoxit or similar and then let it dry and go over them all again with a suitable lubricant (faderlube) etc. While you have the cover off check the earth points on the chassis for cleanliness and tightness, on mine there is the main one below where the power cord socket is, a couple over near main filter caps and at least one or two on sides of chassis. See how you go after this.

 

[greenflash]

Thanks a lot for your tips. WD40 is ok as a lube replacement? I'll see about the earth points that sounds a little more accomplished. For now the good thing is that after some hours of usage the old noise won't come up. Only after turning off/on again and probably just when turning the bass knob.

 

[Oldsansui441]

Thats good the noise is not there after hours of using. WD40 is NOT suitable for this purpose, l am not sure what products you have near you but here in Australia our local electronics stores have these products. l use the product on the left and let dry for a couple of hours, this cleans but also removes any of the lubricant so l then follow up with product on the right. In both instances l work switches/pots to full extremes many many times after applying each product.
l will reconnect my akai am-2650 and see if my bass knob has any such noise, cant remember it doing so though after performing above procedure l remember all switches and pots to be dead quite, (volume knob was very staticy beforehand). Hope this helps in some way.

 

[greenflash]

Thats good the noise is not there after hours of using. WD40 is NOT suitable for this purpose, l am not sure what products you have near you but here in Australia our local electronics stores have these products. l use the product on the left and let dry for a couple of hours, this cleans but also removes any of the lubricant so l then follow up with product on the right. In both instances l work switches/pots to full extremes many many times after applying each product.
l will reconnect my akai am-2650 and see if my bass knob has any such noise, cant remember it doing so though after performing above procedure l remember all switches and pots to be dead quite, (volume knob was very staticy beforehand). Hope this helps in some way.

Helps a lot, thanks! I'll try to find a suitable electronics lubricant down here (Yeah I bet WD40 was not the right product). On several tests, I found out that the bass knob now will only produce a noise when rotated immediately after power up, if I wait 20 seconds or more it won't produce any noise. Does make sense in a way, as there's a power up wait time that should always be observed right?

 

[Oldsansui441]

No worries. It shouldn't do it on power up either. l have just checked mine through headphones on power up and no such issues, all pots and switches are noise free. It would be interesting to know if it does it with the tone controls turned off, l am guessing it wouldn't. When l got mine it had another fault but while l was in there l noticed there were some small blue sanyo .15uF 25v capacitors on the tone control board, these are a known capacitor to fail, l just replaced mine as a preemtive measure, at least one is in circuit with the bass control knob. I am just wondering if this could be an intermittant issue with yours and could explain the noise going away after voltage is applied to capacitor for a certain time, this is only a guess though.
Anyway you are probably not that concerned with such a small fault for first few seconds.

 

[greenflash]

No worries. It shouldn't do it on power up either. l have just checked mine through headphones on power up and no such issues, all pots and switches are noise free. It would be interesting to know if it does it with the tone controls turned off, l am guessing it wouldn't. When l got mine it had another fault but while l was in there l noticed there were some small blue sanyo .15uF 25v capacitors on the tone control board, these are a known capacitor to fail, l just replaced mine as a preemtive measure, at least one is in circuit with the bass control knob. I am just wondering if this could be an intermittant issue with yours and could explain the noise going away after voltage is applied to capacitor for a certain time, this is only a guess though.
Anyway you are probably not that concerned with such a small fault for first few seconds.

Well, today I decided to listen to an LP record on the turntable that's connected to the Akai amp and I had to lift up the volume to the half (not sure why, btw) and there I hear a constant though low hiss. It seems when playing from my computer at a lower volume (quarter of the whole turn), well I couldn't hear it. So kinda back to square one. Tomorrow I will try your tip about turning off the tone controls (set to zero). But I guess I might have to end up taking it to the tech.. Bugger.

 

[Oldsansui441]

That is a annoying, could be something more in depth unfortunately like maybe a transistor or even a capacitor. Sorry l led you astray saying to turn tone controls off, my 2650 has this switch and l thought yours must have also but it doesn't.
Good luck with it, hopefully it isn't anything much, it usually isn't, let us know how you go.