• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Marantz 140 Adjusting DC offset and bias ?

B

Bogdan1986

New Member
Hello guys,im new to this kind of things regarding electronic repairing etc etc, can someone tell me how can i adjust the bias on my Marantz 140? Where do i connect dvm, on which pins ?I have the manual, but to me its unclear where should i connect the digital multimeter in order to adjust the bias.The dc offset i was able to get it to 1mv .
Any help will be highly appreciated.
 
Register to hide this ad
Page 2 of the Service Manual is fairly clear as to where to connect your meter probes and how to make the adjustment. Which part of the procedure are you unclear on?
 
ChrisMarantz said:
Page 2 of the Service Manual is fairly clear as to where to connect your meter probes and how to make the adjustment. Which part of the procedure are you unclear on?
Click to expand...
Hello, i give an example of how to adjust marantz 2235 ,, If you feel everything is ok but the protection relay still doesn't engage, we can go around the relay and make the first adjustments (this will likely fix the problem). Connect the DVM (set to DC volts) to test point 809 (+) and 805 (-) on the power supply board and adjust R713 on the power amp board for 0VDC reading on the DVM.( http://irebuildmarantz.com/classic/html/2235b.html ) ''- Its specifying exactly where i have to connect the dvm in order to adjust stuff. Ive read the manual of 140 and ive seen that i need an osciloscope?
i only have a digital fluke multimeter.
 
ChrisMarantz said:
Page 2 of the Service Manual is fairly clear as to where to connect your meter probes and how to make the adjustment. Which part of the procedure are you unclear on?
Click to expand...
In the manual it says; preset the bias and adjust R742 on each amp board ccw .Turn line switch on and advance variac to 120v.( at this point i gues my digital meter has to be connected to some pins in order to read these values).For Europe should be the same value-120v?
i think i should better let it to an electronist lol.
btw ,, line switch on; i gues is the power cord? what aboout variac>? what is that>?
 
ChrisMarantz said:
OK, lets backup a bit. . . Why do you think that you need to adjust the bias?
Click to expand...
Hello Chris, the reason i would like to adjsut bias is because the right channel is measuring 0.29 Mv and the right channel is measuring 0.5 mv.
Its normal for class AB amplifier that bias is between 0 -0.29mv?
Ive done some adjusting on my other amps like 2226, 2235,2238 Marantz models but this 140 model is a bit more complicated?
Greetings Raul
 
For anyone reading this thread since it went unanswered, as per the manual the pins to connect your multimeter to on the Marantz 140 are J701 & J702. Connect the - lead of your MM to J702 and the + lead to J701 and then adjust potentiometer R742. Hope it helps someone in the future that needs to make Bias Adjustment on Marantz 140.
 
You must log in or register to reply here.
Back
Top Bottom