Akai am-2200 recurring nightmare!
- Thread starter greenflash
- Start date
SpiderHi-Fi
New Member
Hello, hugobny!!!
Sorry for the very big delay in this answer.
I did not receive any notice by email that someone had written again on this post.
As NAD80 says, I connected chassis to ground using the rear connector. The noise disappeared by 99.9999%.
When I said "connecting chassis to Mother Earth", I meant that, of necessity, I had to connect it with a cable to the pipes of an old hydraulic pump in a water well. Literally, my ground is in the deep bowels of the Earth. It was a funny way to say it. I'm sorry I confused you.
Have you noticed if when you run your hand over the amplifier, touching the wooden deck, the noise increases?
Hello !
I'm glad you answered, thank you !
Alright, that is literally connected to earth than, lol ! I imagine that it would have the same effect to connect the chassis to the earth wire of a new line cord; but I'm quite concerned in soldering that to a random spot.
Exactly ! Strangely enough, running my hand over the transformer is increasing the noise.
I'm sure that it's not the normal behaviour for this amp; before recapping it wasn't working well, but it had no noise whatsoever.
That's a strange issue, voltages seem fine according to the service manual though...
I'm glad you answered, thank you !
Alright, that is literally connected to earth than, lol ! I imagine that it would have the same effect to connect the chassis to the earth wire of a new line cord; but I'm quite concerned in soldering that to a random spot.
Exactly ! Strangely enough, running my hand over the transformer is increasing the noise.
I'm sure that it's not the normal behaviour for this amp; before recapping it wasn't working well, but it had no noise whatsoever.
That's a strange issue, voltages seem fine according to the service manual though...
elnaldo
Lunatic Member
If the noise was not present before the recap, of course you need to check the work done. Check capacitors polarity, check picts you have of your unit before the repair, check ground connections, check if some wire was broken while working or moving boards.
If you have just a slight hum, check the wiring layout. Try to run signal wires far from the transformer.
But pay special attention to all the ground connections.
Connecting to earth ground an amplifier without earth ground, could introduce even more hum in some occasions (ground loops not taken into account in the original design)
Check the unit without any source connected to it, just the amplifier.
If you approximate your hand to a high gain preamp (phono or mic), it's normal to hear a hum if volume knob is not at zero position.
If you have just a slight hum, check the wiring layout. Try to run signal wires far from the transformer.
But pay special attention to all the ground connections.
Connecting to earth ground an amplifier without earth ground, could introduce even more hum in some occasions (ground loops not taken into account in the original design)
Check the unit without any source connected to it, just the amplifier.
If you approximate your hand to a high gain preamp (phono or mic), it's normal to hear a hum if volume knob is not at zero position.
SpiderHi-Fi
New Member
(Sorry for SO BAD post. Im writing via mobile phone.) 
When I made first attemp to fix amp (changing only damaged differential pair TR and old light-blue OSCON caps), this static noise was total evident.
When you connect chassis rear screw to the earth wire of your electric outlet, noise reduces or not?
I cleaned ALL wire connections spray-ing contact cleaner over wire-wraps; plus main chassis global ground connection with contact cleaner + 96º alcohol; I moved all cables far of transformer (just a little, cables are not long enough, you know). I left them as they were at the beginning thanks to the photos I had taken. Before and after recapping. 2 times. Nothing worked. Only grounding chassis to earth via rear screw.
(by the way... hi again, Elnaldo!!!!!)
You are in AK. Please let us know which were all the symptons of the patient.
I remember ALWAYS this static noise in my Akai, even before open for the first time the wooden deck. Masked with crackles of failing TR differential pair and "old-TR plus dry OSCON caps" noise of preamp, but there.
When I made first attemp to fix amp (changing only damaged differential pair TR and old light-blue OSCON caps), this static noise was total evident.
When you connect chassis rear screw to the earth wire of your electric outlet, noise reduces or not?
Over main PCB. Use headphones. When hand in left side, more noise in L-Ch. In right side, more in R-Ch. Isn't it?
I cleaned ALL wire connections spray-ing contact cleaner over wire-wraps; plus main chassis global ground connection with contact cleaner + 96º alcohol; I moved all cables far of transformer (just a little, cables are not long enough, you know). I left them as they were at the beginning thanks to the photos I had taken. Before and after recapping. 2 times. Nothing worked. Only grounding chassis to earth via rear screw.
(by the way... hi again, Elnaldo!!!!!)
elnaldo
Lunatic Member
I've repaired 2 or 3 of this same amp, and none of them did any noise, and for sure they leaved the factory without those noises, that's why I think the noise is not generated at the amp. Perhaps some interference in tge line voltage, solved with your ground connection. But in some cases the solution is the opposite, to lift the ground. It depends of the ground loops or ground connection created between the different devices.
SpiderHi-Fi
New Member
Exactly!!! As I mentioned by private message, in my case I think that the repeater's TV broadcasts sneak into the almost 100 meters of aerial parallel and bare copper cable, perpendicular to the repeater. My electrical installation is sure to be a perfect and giant dipole!!!
One day I have to dismantle the amplifier and take it to my house in the city or to the office, where the electrical installation is more modern and is more protected. In none of my 2 Sony TA-V50 do you hear that noise, I imagine that due to a more modern topology and that the box is totally metallic (a perfect Faraday cage).