Yamaha B-4 power amplifier

[Ytamshb]

Can anyone have this model of yamaha amplifier b-4 i want service manual for this amplifier.
I need to adjust DC Balance voltage/ Bias voltage without manual I don’t know how to do that which voltage suitable for each VR adjustment can anyone help me ???

 

[clinic-audio]

Hello Ytamshb

I am sure that you know it, but the YAMAHA B4 is a product manufactured for Japan market only
If you are looking for it ask Japanese market

 

[avionic]

Can anyone have this model of yamaha amplifier b-4 i want service manual for this amplifier.
I need to adjust DC Balance voltage/ Bias voltage without manual I don’t know how to do that which voltage suitable for each VR adjustment can anyone help me ???

Post a clear enlarged photo of the driver boards. See if we can figure it out without a manual.

 

[avionic]

I'm thinking that you can use the M-4 service manual . for test points and likely DC offset and normal idle current. Class A idle current. I'm not sure at the moment.

Yamaha M-4 DC Offset

Picked up a M-4 power amp. Appears to be clean and fully operational, the input level pots will need a shot of Deoxit but that is about it, I think. The DC offset is 35mv and 77mv, not terrible from what I have read, but could be better. I see a couple of pots marked "DC Balance" that are just...

audiokarma.org

 

[clinic-audio]

Hello Dave !

here are the requested pictures

 

[clinic-audio]

Hello Ytamshb

Don't forget that this is a 100V unit not 110V

 

[Ytamshb]

Hello Ytamshb

Don't forget that this is a 100V unit not 110V

I want to know voltage adjustment each VR

 

[clinic-audio]

and do you have the adjustment location point ?

 

[Ytamshb]

and do you have the adjustment location point ?

Yes i see them but I don’t know without manual whichever voltage to set for each vr

 

[hdeart59]

Can anyone have this model of yamaha amplifier b-4 i want service manual for this amplifier.
I need to adjust DC Balance voltage/ Bias voltage without manual I don’t know how to do that which voltage suitable for each VR adjustment can anyone help me ???

Hello everyone! You can see the quiescent current for class AB in the Yamaha M-4 service manual. I can calculate it for class A, it's not difficult. We still have a holiday in Russia. I'll post the data later.

 

[hdeart59]

For Class A there should be 322 mV between points CT and NE. This gives 30W in class A into 8 ohms.

 

[hdeart59]

Adjustment in class A is carried out by trimmer resistor VR404.

 

[hdeart59]

According to the Yamaha M-4 manual, the voltage at the CT and NE points should be 15 mV +/- 2 mV. This also applies to the Yamaha B-4 in class AB. Adjustment in class AB is carried out by the trimmer resistor BP402.

 

[hdeart59]

Sorry, VR402.