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SONY STR 7055 Low Left Channel

omri617

omri617

Super Member
Hi
The Left channel is significantly lower in volume and not musically detailed as the Right channel.
All pots and switches were cleaned.
The STR-7055 has a SEPARATE & NORMAL switch which I used for using the receiver as Pre/Power amp.
After trying both variations i came to conclusion that it's the pre-amp.
Any help what should I be testing would be very appreciated.
Thanks
 

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Some of the switches are a combo of rotary and board-mounted sliders. Did you clean the sliders?
 
It may not be the switches then, but I've had a similar problem caused by switches on an STR-7055: low volume or dropout, rather than noise. Those sliders take some serious acrobatics to get contact cleaner to the contacts inside, if you're not going to remove them from the board to clean.
 
Ok went ahead and swapped between pins 41&42 on the volume board and now the low channel became the Right channel.
 
omri617 said:
btw there’s no sliders in it
Click to expand...

Ah, but there are sliders.

The SPEAKER, FILTER, FUNCTION and MODE switches are all, as I mentioned previously, combination rotary/slide switches. The sliders are mounted directly to the control board, so it's easy to clean the rotary portions, overlook the sliders, and mistakenly believe that all of the switches have been cleaned.

If you're very patient, skilled with desoldering and soldering, and comfortable with disassembling and reassembling components that were not designed to be taken apart, you can remove them from the board (around 60 pins each) take them apart, clean, reassemble and reinstall them. Otherwise, you can try cleaning them in place (which is not particularly easy, either.)

There are very few places to get cleaner inside the sliders, and none of those points are especially near the contacts. If you remove the bottom cover and look at the solder side of the board, you can see the pin locations, which should help you locate the contacts. It's possible to tip the unit and inject the cleaner in such a way that it will run down to where the contacts are. (As I said, acrobatics.) I've found that repeating this procedure for each switch a few times, exercising the switch in between, can clean the contacts on the sliders.

A follow-up application of faderlube, using the same method, can help keep the sliders lubricated.
 
Ah sorry I thought sliders are more like the Marantz has for the Balance in some units.
I will clean them again, but I’d like to know it if there Is a point where I can connect the signal path Wires to check where more or less the problem is.
 
omri617 said:
Ok went ahead and swapped between pins 41&42 on the volume board and now the low channel became the Right channel.
Click to expand...

By the schematic, what test I can perform on the volume board to rule out the volume board that it’s not faulty?
 
Is there a transistor or capacitor in charge of the balance? The right channel is extremely high and left is extremely low
I replaced the volume pot and board from a working unit and no change in sound
 
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