Yamaha CA 810

Audi2014

Audi2014

Active Member
Finally got my Yamaha CA 810 project up and running.I have noticed that the
left channel is way too loud.Connected a set of rca jumpers to the main and
pre amp connections.Swapped connection and problem just swapped to a
different channel.Pointing to a pre amp issue.Checked idiling voltage and got
both channels to around 14.5 as per service manual.Can anyone shed some
light on this issue?
 
Audi2014 said:
Finally got my Yamaha CA 810 project up and running.I have noticed that the
left channel is way too loud.Connected a set of rca jumpers to the main and
pre amp connections.Swapped connection and problem just swapped to a
different channel.Pointing to a pre amp issue.Checked idiling voltage and got
both channels to around 14.5 as per service manual.Can anyone shed some
light on this issue?
Click to expand...

A dirty switch or control in the signal path are a prime suspect.
 
Hi, there are to screws on the balance knob. They are hidden, but you can access them from the side by twisting the knob, right behind the front panel.
 
Thanks.I found the set screw.I was just looking at it.Issue with one channel louder than the other only happens in stereo mode.When I switch to mono mode
both channels equal out and music level is pretty much the same.
 
I ran a audio signal into the main in connection at the back of the unit.
Same issue..left channel is totally louder than right.This is pointing to a amp issue.I did notice that it happens once the unit has warmed up after a few
seconds.
 
Can you also check mid-potential (DC Offset)?

9jqh5z.jpg
 
Mid Potential Voltage

Hi,
Thanks for checking out this thread.Will check in the morning and give you a
reply back.If reading is not 0VDC, how can I adjust?Also, am I checking regular
DCVoltage, or am I setting my meter to 300Millivolts like I did when I tested
the idle voltage?
 
Hi,

If the mid-potential is not reading 0V, you need to replace a few transistors, check some diodes, etc.

If your multimeter is not of auto ranging type, you can set it to 20VDC or maybe 2VDC. It has to read zero volt, so not a big problem.

The CA-810 has a concentric Volume/Balance potentiometer that sometimes both left and right membranes might be "misaligned" with the resistive material inside. So one channel can be a bit louder (or quieter) than the other.

You can check it with the multimeter (set in Ω Ohms) with one probe on each wipers (L + R) at time, and with the other probe on the other terminals. See if the channels have the same resistances along the way. If one has less resistance than the other, than THAT ONE will sound louder.

ujwa.jpg
 
Most of the CA series I usually need to disassemble and clean the Input Select SW as well as the MODE switch to get them working right. You can't get the cleaner where it will do any good without disassembly, unless you submerge the switch in cleaner/deox-it.
 
If the mid-potential is not reading 0V, you need to replace a few transistors, check some diodes, etc.
Click to expand...

Even then, you probably will not achieve 0 volts. And it will not remedy your issue with low volume on one channel.

Read over EW's thread concerning dc offset.
http://www.audiokarma.org/forums/showpost.php?p=43466&postcount=1

0 - 15mV: Damn good!! If you read '0V', you may have a capacitor output, or your meter is set wrong

16mV - 50mV: An acceptable value, especially at the lower end of this range. 2nd harmonic distortion is probably twice to four times what manufacturer's spec calls for at higher frequencies. Probably not audible, as the distortion is mostly in the upper octaves. At the upper end of this range I begin to raise an eyebrow.

50 - 85mV: Something is certainly amiss, and while this is not enough to put your speakers or equipment in jeopardy, the amp is running nowhere near where it should. I'd venture to guess that most of the DC-coupled amps that are in use by forum members here fall into this range.

100mV to ?: A high enough voltage will cause the DC protection to kick in. This happens at a level determined by the designer, but is usually equivalent to about a diode drop (600mV)or so. Needless to say, if you are listening to an amp with 100mV or more of DC offset, you have no idea what the amp really is supposed to sound like. Indeed, some amps without a differential input are actually designed to have a bit of DC at the outputs, but this is triple-rare, and I don't think anyone here owns one. (in my book it's piss-poor design, but if you can sell it WTH..)
Click to expand...
 
Last edited:
avionic said:
Even then, you probably will not achieve 0 volts. And it will not remedy your issue with low volume on one channel.
Click to expand...

True, and probably has nothing to do with the problem at left channel... Just normal procedure in checking if everything is adjusted to the optimal...

Audi2014, now I saw your post:

Audi2014 said:
I ran a audio signal into the main in connection at the back of the unit.
Same issue..left channel is totally louder than right.This is pointing to a amp issue.I did notice that it happens once the unit has warmed up after a few
seconds.
Click to expand...
That's a good problem... Reminds me a transistor that went short in an amp I had causing similar effect.

A few things to check...
 
DC Offset

Good morning,
I did a dc offset test after I checked my idling voltage which was around 14
mvdc.The dc offset voltage I am getting is: Left Channel: 11.5mvdc
Right Channel: 5.7 mvdc.
 
Transistors

I just took some pictures of the Left Channel Board.You will see 2 transistors mounted to heat sinks, and 1 I removed.
Bounced good readings from Right channel transistors and these 3 came into question.What can I use to reattach the heat sink to the circuit board.
 
Last edited:
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