Yamaha A-760 II, DC-Offset rising up to 1200mV

[darko]

Replaced the last one Cap. C311.

Dirty Texture on the Schematic ... Not recognized ...
Bad Detail Recognition, bcause cheap Zoomfactor.
( too many little Pixels around the Component Number )
C318, or C315? No, it is the C311...


Now we have : Right Channel 19mV; left 0.4mV



Have nice Weekends, Guys

Cheeeers,
Darko

ps: the Main Bulb ( Power-ON ) is allready gone -> to much Current?
Is 1 gone, all are gone -> its a Serial Chain of Bulbs .. very nice :0)

 

[packrat]

Good to hear it's fixed!
:yes:
So what exactly fixed it? The last bad cap, or that optocoupler you mentioned?

 

[darko]

Hi Packrat,

I cant say, sorry :-/


The only Thing I for shure can say is:

Diana Krall have a very nice Voice ))
(Yes, I like her Voice too!)

The biggest DC-Falldown was after replacing the last Cap, C511.
He was placed so bad, that I have to remove a Metal-Platen, that holds
mostly Everything together :-0.

How much a Optocoupler can distort only one Channel is not in my
possibillity to explain - Iam shure a Pro can.

I never measure each single Circuit Group.
So, possible is a Resonance-Loop somewhere.
The most Electrolyt Caps, I have replaced,
was in the Near of Heat-Sources, like Power-Resistors.-> nice BBQ ..

Strange is, that 98% Caps has a good C-Value.

Tip: for better and shorter Heating-Up-Period,
I cover the whole Amp with a "Not inflammable" Towel.

After playing 3 CDs, the DC-Offset was in the Right cHannel only ~17mVDC.
In the Left Channel more less: 0,4-0,1mVDC.

The Yamaha A-760 II can go back to his Owner now.
( .. and I can fix then a Sony 1140 with Coupler-Cap Issues (static Noise))

Have a very nice and peacefull Weekend,


Darko

 

[darko]

One Thing I forgot:

- The Amp have now the Original big ELNA Caps back.


At Repair, I replaced both with Industrial Purpose Caps with 18000uF - 63V.

With the ELNAs, the sound is more crisp a maybe more clear -
but You know, its a strange Thing with Psychoaccoustics.
Today it sound bad, same Thing than Tommorow is another Story.



Darko