Anyone w/ 2250B know where to measure bias

[RobD8870]

I have a Marantz 2250B. I do not have the manual. Not really sure where I should be measuring bias at? I know where the pot for offset and bias are. Also I am not sure what value I am wanting on the bias. I dont want to pay someone for a cop of a manual. I cannot find the manual anywhere online(for free).

I measured at the bias pot....got .784. I can adjust but am not sure what value I want the other bias pot measures .9 I do not think I should be measuring at the pot I have looked quite a bit and am still coming up empty....hopefully someone is out there with this info!! Thanks

BTW, I know that if I mess up my equipment it is on me. I also have everything where it came. You can see dirt mark where they have been set so that is nice....I need to clean them up but for now it is nice to have a reference point.

 

[RobD8870]

R719 is the bias....R707 is offset......Anyone that has any idea? Thanks. I have always noticed that the left channel has more punch. Also when I run the receiver for a while the left heat sink gets warm and the right is not warm at all.

This would seem like a bias problem? correct? I can post pics...

 

[RobD8870]

UPDATE: Found this while digging through everything. I have not had a chance to make the adjustments but I am hoping I am squared away!!! Figured I would post in case someone else was wondering.


"Actually reading a post of Echowars, he stated for idle current adjustment, J754 and J760 and set it for 10mv. Not 5mv as it states in the manual.


Someone asked about the 2250B. The manual states for voltage adjustment,
place meter leads at terminals 804 and 805 and adjust R806 for 35V DC.

DC offset - connect leads between speaker terminals and adjust R707 for 0V DC.
Idle current adjustment - connect meter between terminals 708 and 710. Adjust trimmer R719 for 10V DC. After setting, check DC offset again and adjust if necessary. This manual is correct for these adjustments."

Posted by RocknRum In another thread....

 

[RocknRum]

Connect your meter between pin terminals 708 and 710. You want 10mv DC.
After adjusting check offset again. Your correct in the trim pot identification.

 

[RobD8870]

Hey Rock...I measured across R708 and R710..There is no J708 or J710..if I set it to 200mV it reads 1....if i set it to 200v it reads 38.3. that is on both channels..DC values ofcourse. the bias pot does not seem to affect these readings. I have to be doing something wrong. ?

 

[RocknRum]

Check your PM.