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Sansui B-2301 DC Offset

edman

edman

Active Member
Hello,
I just bought a Sansui B-2301 and was wondering if anyone would happen to have info on how I would go about checking the voltage and setting the DC offset on the B-2301? I don't have a bias meter or I would check that also. I downloaded the Japanese service manual. Thanks for the help.
 
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Page 13 on the service manual, shows the back of the amp , and on the right side of the page there is a photo , where it shows the various vr's for bias and dc offset.
Bias is separate for cold and hot on each channel, and dc offset exists on each channel and on the back of the amp also. So there are 6 trimmers to play and set dc offset.
 
Thanks javman. But like Hyperion says it's only schematics - not a complete Service Manual. JOMARK911 I should have known if anyone would have or know where to get the info you would lol. I just need to know where I place the + and - probs? So it sounds like I will be able to use my Multimeter to check and set both Bias, and DC? I hate to be a pain but since I am unable to find a Service manual written in English I am kind of left in the dark. I appreciate the help.
 
Hi JOMARK911 I have recapped the same amp., and is doubting how to do the adjustments the right way. I do have the complete japanese service manual but do not understand japanese. Is it possible for you to explain for me how to do ?
 
There is nothing special . Turn on let the amp warm up for 20mins perform the dc offset first and then the bias adjustment.
Then recheck the dc offset and then recheck the bias.For bias use the test points on each driver board. There is one on each end of the board, since there are two channels in each board.
 
I would check the bias 2-3 minutes after powering-on the amp....NOT adjust as per service manual recommendation right then, just check to be sure that it doesn't have too much or too low bias from a possible previous wrong setting.....simply because there is no point to "cook" the output transistors for 20 minutes or more in case there is too much bias....or to have them too "cold" when trying to adjust because bias was too low. It's about thermal equilibrium.
So, again, I would do this just to be sure that 2-3 minutes after power-on bias is let's say +/-20% from the value specified in the service manual. Eventually adjusted to be in those +/-20% from the specified value, if it is way off (too high or too low). Then re-checked and adjusted to service manual spec after 20-30 min warm-up, as Jomark911 said earlier.
Just a personal preferred way of doing it.
 
JOMARK911 said:
There is nothing special . Turn on let the amp warm up for 20mins perform the dc offset first and then the bias adjustment.
Then recheck the dc offset and then recheck the bias.For bias use the test points on each driver board. There is one on each end of the board, since there are two channels in each board.
Click to expand...
Thanks for your quick reply :-)
 
Read this hole thread first. There are some useful info, like input selector to off, and level knobs to min , at the back of the unit , but i guess you already know this.
If you have any difficulties late us know.
 
edman said:
Hello,
I just bought a Sansui B-2301 and was wondering if anyone would happen to have info on how I would go about checking the voltage and setting the DC offset on the B-2301? I don't have a bias meter or I would check that also. I downloaded the Japanese service manual. Thanks for the help.
Click to expand...
Hi,
Can someone please let me know the value of the Variables used in driver board & input board, I think need to be replaced due to age of amp by multi turn good quality variable to adjust the Bias & offset perfectly.
Also there are 4 of variables on each driver board, how to adjust the Bias & offset, can some one put light on the procedure of Bias & offset.
Thanks in advance.
 
yadvinders said:
Hi,
Can someone please let me know the value of the Variables used in driver board & input board, I think need to be replaced due to age of amp by multi turn good quality variable to adjust the Bias & offset perfectly.
Also there are 4 of variables on each driver board, how to adjust the Bias & offset, can some one put light on the procedure of Bias & offset.
Thanks in advance.
Click to expand...
First please download a copy of the Service Manual, you will need it. It also contains the DC and bias setting guides even though it might not be 100% clear how to do it.
In it you will find the following values for variable resistors:
1703868861257.png

Sansui B-2301 Stereo Power Amplifier Manual | HiFi Engine

www.hifiengine.com www.hifiengine.com
 
Magnus Back said:
First please download a copy of the Service Manual, you will need it. It also contains the DC and bias setting guides even though it might not be 100% clear how to do it.
In it you will find the following values for variable resistors:
View attachment 3073949

Sansui B-2301 Stereo Power Amplifier Manual | HiFi Engine

www.hifiengine.com www.hifiengine.com
Click to expand...
Thanks for the update, just curious to understand why 4 variables on the Driver circuit board, generally there are 2 variables for DC offset & biasing
 
yadvinders said:
just curious to understand why 4 variables on the Driver circuit board, generally there are 2 variables for DC offset & biasing
Click to expand...

Because B-2301, like any other Sansui Alpha/X-Balanced, is a balanced-output amplifier, not like the "normal"/usual topology. If you didn't figure that out by now, well, you may be in for a "surprise", more or less. Just be warned that this is not an "usual" amp and, consequently, don't threat it like being so.
These older posts may be helpful, there are some diagrams there, and really no need to re-write everything again here:

what happened to the Diamond Differential circuit, was it improved, simplified

Ltspice for simulation X balance floats the speaker so it acts as a bridge effectively having the same voltage across the load Thanks for the response. Just to try to understand this. When I look at the schematic of for example the AU D77X I can see what you say because you have the +35 and -35...
audiokarma.org

what happened to the Diamond Differential circuit, was it improved, simplified

Ltspice for simulation X balance floats the speaker so it acts as a bridge effectively having the same voltage across the load Thanks for the response. Just to try to understand this. When I look at the schematic of for example the AU D77X I can see what you say because you have the +35 and -35...
audiokarma.org
 
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