Yamaha A-960 question

that70sguy

Well-Known Member
I recently acquired a Yamaha A-960 integrated amplifier and can't find much info on it. My question is - what does the "Main Direct" switch do? There may be a problem with the amp as when I select the Main Direct it shuts off the amp. Selecting it again turns it back on again so it's basically working as a power switch. I pretty sure that's not the intention as there already is a power switch. The amp works fine and sounds beautiful, but want to know the deal with the Main Direct switch and what I'm missing by it not working. Also it doesn't light up green like it's supposed to either. Can anyone offer some help or suggestions?
thanks.

Jay
 
The main Direct switch bypasses the filters, tone and loudness circuit, and mono/stereo switch.

The first thing to check is the position of the variable loudness control. If this loudness control is at its minimum position (maximum attenuation of 20 dB at 1 kHz), you may think something is bad in this amp when this switch is on.

As usual, the second thing to is a good contact cleaning job.
 
Here is the Block Diagram of the A-960
 

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The Main Direct switch is supposed to lead the audio signal straight from input to main amp; only the volume knob is between the amp and source. All tone control circuits are bypassed to ensure the best quality sound.

The A-960 also has a Disk Direct witch does the same, in this case just only connecting the TT input straight to the amp.

---------------Edit----------------
Note: as seen on the block diagram the loudness function is bypassed with Main Direct, only balance is in there.
 
Thanks for all the info guys! Since it works perfectly fine without using Main Direct, I would assume that there's no problem with the amp. I guess I just have to trace it from the Main Direct switch.

Also, the amp gets pretty warm when left on, but not in use. Not hot, but definitely warmer than my Mac MC2105. Is this normal?
 
The A-960 has three adjustments for Idle and Offset, details are in the shop, if they are off that could cause heating. This was changed somewhat with the A-960 II.
 
Thanks for all the info guys! Since it works perfectly fine without using Main Direct, I would assume that there's no problem with the amp. I guess I just have to trace it from the Main Direct switch.

Also, the amp gets pretty warm when left on, but not in use. Not hot, but definitely warmer than my Mac MC2105. Is this normal?

I had the Yami A- 1060 and it used to get so hot it would shut down. Last year I dragged it out of storage to be repaired. The Tech. told me the circuit board was burnt and needed replacing.
 
I recently acquired a Yamaha A-960 integrated amplifier and can't find much info on it. My question is - what does the "Main Direct" switch do? There may be a problem with the amp as when I select the Main Direct it shuts off the amp.


Hi Jay


Inspect if your source doesn't have DC offset . If it does, when you press the main direct, this DC put the main amplifier in protection mode...
 
If you have a DVM here is how to set the idle and offset; on the mainboard just back of the big filter caps are four variable resistors numbered left to right VR303, VR301, VR302 and VR304. Just left of VR303 are two test points, TP1 on the left TP2 on the right. Similarly to the right of VR304 are two more test points, TP4 on the left and TP3 on the right. So much for geography.

Set Volume control to minimum (0)

Idling current: Left Channel;
Connect DC voltmeter between TP1` and TP2, adjust VR303 for 10mV plus or minus 3 mV

Right Channel;
Connect DC volmeter between TP3 and TP4, adjust VR304 for 10mV

DC Offset; Left Channel;
Connect DC voltmeter between TP2 and the chassis, adjust VR301 for 0V

Right Channel;
Connect DC voltmeter between TP4 and the chassis, adjust VR302 for 0V

That should cool it down some.
 
Yes, you may have a DC-Problem. Maybe also important for you: Yamaha Europe (Germany) has recently made a security warning for owners of vintage Amps with X-power supply (760, 960, 1060, B6). A capacitor in the power supply may explode (this is what happened in one of my B-6, what a mess).
 
Thanks again to everyone for your help, it is much appreciated.

Yes, you may have a DC-Problem. Maybe also important for you: Yamaha Europe (Germany) has recently made a security warning for owners of vintage Amps with X-power supply (760, 960, 1060, B6). A capacitor in the power supply may explode (this is what happened in one of my B-6, what a mess).

Doc, do you know what they recommended as a fix or update, if any?
 
LOL this must be under the "better late then never" rule :)

But I guess the M-70 and 50 has to be put in the danger zone or did Yamaha specific mention the (760, 960, 1060, B6)?

And do you have the service bulletin?
 
Doc, do you know what they recommended as a fix or update, if any?

At least the A-760 has a X-cap (0.47yF) on one of the power supply boards. This is a rather large, rectangular and yellow/gold colored cap. Probably there are already damages visible. Just replace it with a new X2 (!!!) cap of the same value. There are probably other, smaller caps looking similar (rectangular, golden). There is no need to replace them, just the single 0.47 cap over the mains.

Martin
 
I think the capacitor in question is C501 (I don't recall were I saw this info). It is part of the RF suppressor connected directly on the power line input.

In the A-960, the general model has a 0.22 uF / 250 VAC

The North European, Australian and British models have a 0.47 uF / 250 VAC capacitor.

This 250 VAC rating is too close to the line voltage in some contries to give safe margin. Replace it with 400 VAC cap
 
The A-960 has three adjustments for Idle and Offset, details are in the shop, if they are off that could cause heating. This was changed somewhat with the A-960 II.

Here is a reprint of the Adjustments procedure and Adjusting points from the A-960 service manual (to follow since my actual file is too large!)

Merrylander, would it be better to adjust the A-960 according to the A-960 II procedure?

What are the differences between the two adjustments procedures?

Thanks!
 

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Here is a low resolution but readable Adjusting points sheet from the A-960 service manual
 

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A-960 II adjustments

HI,

I recently acquired an A-960 II integrated. I has a failed balance slider, but I bypassed the slider and got it working. After reading this thread, I wonder if any of you have some A-960 II information. Particularly adjustment procedures or schematics.

Thanks,
John
 
That seems to be a common problem with this model. I have the adjustment procedures but they will need to be scanned and converted to PDF.
 
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