I’m looking to replace the electrolytic caps in my amplifier (Akai AA-5510). I’ve heard that you should adjust bias and DC offset if you replace the capacitors in the amplifier stage. Is that right?
For reference this is the schematic for the main amp board:
I have little/basic electronics knowledge so any help is appreciated.
Also, do you need an oscilloscope to adjust bias and DC offset? I only have a digital multimeter.
Thanks
For reference this is the schematic for the main amp board:
I have little/basic electronics knowledge so any help is appreciated.
Also, do you need an oscilloscope to adjust bias and DC offset? I only have a digital multimeter.
Thanks
Why are you replacing the capacitors in the first place? Because everyone says you should "recap" no matter what? Especially when you have little electronic knowledge you should think twice before you start soldering on a working amplifier. Note this is a very classic (I mean primitive) design. There is no short-circuit or overload protection. Any mistake can blow TR2 thru TR6 in an instant.
So... only if you experience lack of low frequency output you could replace C8. Or (less likely) C1 Defective or low value for C7 reduces open-loop gain for the lowest frequencies and might cause distortion. Hum can be caused by a defective C3.
Since you have the manual, the bias current should be mentioned somewhere. Adjustment is not necessary because you change capacitors. But it is good to check it anyway because components might have aged over the years. If no value is mentioned 50mA is a safe bet.
Offset is self-explanatory. You don't need a scope. Analog meters are to be preferred over digital.
So... only if you experience lack of low frequency output you could replace C8. Or (less likely) C1 Defective or low value for C7 reduces open-loop gain for the lowest frequencies and might cause distortion. Hum can be caused by a defective C3.
Since you have the manual, the bias current should be mentioned somewhere. Adjustment is not necessary because you change capacitors. But it is good to check it anyway because components might have aged over the years. If no value is mentioned 50mA is a safe bet.
Offset is self-explanatory. You don't need a scope. Analog meters are to be preferred over digital.
The amplifier has a capacitor in the output and you have no problems with it. So any off-set will not damage your speakers. If you do not hear any marked distortion, the the bias is probably still fine - Now tell us again, why is this amplifier itching you to adjust something. Like the previous writer say, if it is working why break it.
If you really feel the need to replace the input and output capacitor, but get the orientation + and - correct else they may explode in a not so long while. If you hear anything terrible, then consider it, but if I were you I would rather invest in a newer more modern amplifier if you have the funds. But again why the need if this is still working good.
If you really feel the need to replace the input and output capacitor, but get the orientation + and - correct else they may explode in a not so long while. If you hear anything terrible, then consider it, but if I were you I would rather invest in a newer more modern amplifier if you have the funds. But again why the need if this is still working good.
Thanks jlinkels. I am a bit apprehensive about the endeavour so I’m not committed to doing it yet, hence the questions.
Basically yes though, I keep hearing people say things like “i would replace any electrolytics after 20 years”, and that not doing so may cause unexpected failure, or at minimum there may be subtle degradation in sound quality. Since this amplifier is about 50 years old, i figure it would be important to service it.
I don’t have any particular issue with the amp’s performance currently actually, other than some quiet white noise at idle, so recapping it is very much preemptive action. Is this not recommended?
Basically yes though, I keep hearing people say things like “i would replace any electrolytics after 20 years”, and that not doing so may cause unexpected failure, or at minimum there may be subtle degradation in sound quality. Since this amplifier is about 50 years old, i figure it would be important to service it.
I don’t have any particular issue with the amp’s performance currently actually, other than some quiet white noise at idle, so recapping it is very much preemptive action. Is this not recommended?
White noise is not a capacitor issue, it is deterioration of active components with age. Probably TR1.