Yamaha dc offset adjustment? (pics)

Im a little over that, but not much. I was going to just set it at 20mv and run with it. After your post I know for sure that what I'll do. If it sounds under biased, I'll go another 5mv. Thanks for the help!!
 
Im a little over that, but not much. I was going to just set it at 20mv and run with it. After your post I know for sure that what I'll do. If it sounds under biased, I'll go another 5mv. Thanks for the help!!

You'd better learn how to use your meter, because Idle Current IS NOT IN VOLTS.

milliAMPS!
 
The emitter resistors are 0.22 Ohm in the CA-400. So, the bias adjustment for the CA-400 corresponds to a bias current of 20mV / (2 X 0.22 Ohm) = 45mA

In the CA-510 schematic, I can read that the emitter resistors are 0.47 Ohm but I can't find the power transistor's identification. What are they?

45 mA is not a small bias current, it requires a rather efficient heat sink.
 
Maybe you should learn a little more about bias current Martin.Ca. Some measurements for it are taken as mA reading and some are done as a mV reading. It varies from manufacturer to manufacturer. When taken as a mA reading you are simply measuring the current being pulled "through" a given set of points. When the manufacturer asks for a reading for bias current to be done as a mV reading, what you are doing is simply reading the voltage "across" the emitter resistors on the output resistors for a voltage reading. The drop across the resistor is directly related to the value of the resistor. You can then set the "current" based on this "voltage" measurement. For example, Ohms law dictates that: VOLTAGE/RESISTANCE=CURRENT, (example, 20/5=4). Lets say(theoreticly) a manufacturer wants an idle current of 4a, but gives you a spec of 20v for the current bias (voltage spec to set current you say? YEP! keep reading). So you would be measureing the voltage across the emiter resistor which happens to be a 5 ohm resistor and then making your adjustment until you got that 20v reading. 20v/5ohms=4a, exactly what the manufacturer wants it set at. It's called "Ohms Law", google it, it can be your friend, learn to use it! By the way, you can use this procedure for any amp regardless of weather the spec is given in mA or mV. If its given as ma, but its easier to just get to the emitter resistors and measure across them, just use Ohms law to get the voltage number you will need to be hitting. Using the numbers from above, Ohms law says VOLTAGE X RESISTANCE=CURRENT. So....you are given a spec of (using the numbers from the above theoretical example again) 4A for the idle current but just want to measure the voltage across the 5 ohm emitter resistor. Well 20V X 5OHMS=4A. You would just adjust adjust your trimmer until you get 20v across the resistor. It's the same results as trying to set the current using the other way. BTW Martin.Ca......the link to the manual in your post gives you a mV spec, not a mA one! Look for yourself. Also the test points that you measure from are directly connected to one end of an emitter resistor, so you are measuring across the emitter resistors of the output transistors for a voltage reading. Again look at the schematic for yourself and you will see. Thanks for the link, it was very helpful.
 
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You really need this...
328949173_o.jpg
 
The emitter resistors are 0.22 Ohm in the CA-400. So, the bias adjustment for the CA-400 corresponds to a bias current of 20mV / (2 X 0.22 Ohm) = 45mA

In the CA-510 schematic, I can read that the emitter resistors are 0.47 Ohm but I can't find the power transistor's identification. What are they?

45 mA is not a small bias current, it requires a rather efficient heat sink.

The resistors in the CA 610 II, which is what I have are 0.47ohm.

So......20mV/(2 X 0.47 Ohm)=21mA

I should be safe with 20mV. My gut told me 20, I just should have gone with my felling about it I guess. I'll set it for 20mV and let it rip :thmbsp:. Thanks guys!! :yes:
 
This thread started about the CA-510...

"So what is the idle current on this amp supposed to be set to? Nobody mentioned it here. Thanks!"

"The resistors in the CA 610 II, which is what I have are 0.47ohm."

Please, could you respect the original thread?

Maybe you should learn a little more about bias current. ... Ohms law says VOLTAGE X RESISTANCE=CURRENT. So....

I don't think we have too much lessons to learn about Ohm's laws from you...
 
this thread started about the CA-510...


Please, could you respect the original thread?

You might also take note that the bias setting for the CA 610 is the same as the CA 510. Look at post #1 and notice the emitter resistors in the picture. Just an FWI for anyone ELSE out that that didnt read the thread well enough to pick up on that.
 
Hmm? I was concerned about the difficulty of adjusting idle current when the multimeter is set to Volts.

Shall I take myself elsewhere?

No, your post was very helpful, thank you. Without that link I was just guessing that I need to adjust for about 20mV based on the pictures of the emitter resistors in post #1, but your post confirmed it for sure! So, thank you! It adds important info for others out there as well.
 
Having a copy of the service manual will help. You can try calling Yamaha and checking, when they've had it in electronic form they've emailed it free of charge.

and I'm embarrassed, checking what Yamaha manuals I have, (not ca510), indeed your meter should be in mV for idle current. my apologies.
 
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The correct bias adjustment, specific for the CA-610II is:

10 mV ±3 mV, measured across ONE emitter resistor of 0.47 Ohm. Translates to 20 mA ± 6 mA

Between test points TP1 and TP3 (R521), adjust with VR481

Between test points TP2 and TP4 (R522), adjust with VR 482

Peace,
 
Looks like I better get in there and readjust :yuck:. Thank you for the update!
It looked as if the test points were across 2 resistors. Upon closer inspection I see it is only one. It seems to be working fine, but I don't want to take any chances. Thanks for the info :yes:.
 
Sorry to bump an old thread but...

Did anyone else catch the error in the service manual?

I agree with ecluser's above statement. My copy of the SM tells you to monitor the bias across the wrong test points.

Yamaha CA610-II Bias Settings.png
 
Sorry to bump an old thread but...

Did anyone else catch the error in the service manual?

I agree with ecluser's above statement. My copy of the SM tells you to monitor the bias across the wrong test points.

View attachment 780825
Glad you pointed this out, I am working on my CA 610 II trying to get one channel working properly. Plays fine at very low volume, but one channel gets raspy and distorted when you turn the volume up . With constant input signal to both channels the output increases on both channels as you increase volume but one channel then drops off and will not go any louder. Just down loaded the service manual and about to check the Idling current adjustment.
 
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