Sansui Frequently asked, and more...
- Thread starter Morden2004
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vintageboy
Chicago HiFi
great job and thanks for showing us
this thread is really full of great advice. right now I am trying to do the Bias offset for my 881. I have a very basic question, please forgive me if it is too basic :
1. using a DC multimeter, do I have to take out the fuse (f07 & f08) first then measure and do the adjustment at VR03 & VR04?
if I take out the fuse, will it still work ? I am really confuse.
2. according to fig 3-2: so we have to put the red wire to the plus terminal and black wire to the minus terminal of the fuse ? is there any +/- sign on the fuse ? what happen if we put the wrong color wire lead?
thank you in advance for your answer
1. using a DC multimeter, do I have to take out the fuse (f07 & f08) first then measure and do the adjustment at VR03 & VR04?
if I take out the fuse, will it still work ? I am really confuse.
2. according to fig 3-2: so we have to put the red wire to the plus terminal and black wire to the minus terminal of the fuse ? is there any +/- sign on the fuse ? what happen if we put the wrong color wire lead?
thank you in advance for your answer
mroboto
Super Member
For step 1 and 2,do as indicated in the figure 3-1 (use mV meter) (for DC offset) 0V "if possible" on the speakers terminals.
For step 3 and 4,do as indicated in the figure 3-2 (use mA meter) (for bias current).
Bias current is mesured as -30mA instead of 30mA (with my auto range digital multimeter).
Last edited:
mroboto
Super Member
Remove the fuse and place your mA (milliAmpere) tester to act like as if it is the fuse.
(A current measuring fuse)
Last edited:
jd-audio
Well-Known Member
Thank you!
TTomanto123
Member
Can anyone confirm where I test Bias Current on G-5700? The top view from the service manual copy I have is not good. Pretty certain the L channel terminal 85 and R channel terminal 86 are the posts wired gray and blue respectively, but where is the other connection made? There are two holes, with metal visible within, marked as R71 (L), and R72 (R) respectively, but I get radically differing readings dependinG on which probe I place where. New AAs in the DMM. Also, should the pots VR01-04 be given the de-oxit bath and gold lube? Thanks gents.
OverLoad
High On Solder Fumes
Measure across a .33Ω emitter resistor on the output transistor board of each channel and set the bias for 3.3mV's. You can clean the trimmers yes but be sure to set them for minimum bias when done and then go about your measurments/adjustments.
TTomanto123
Member
Thanks OL. To do that I clip onto each leg of the resistor itself? Will the value be marked on the circuit board, or will I need to ID by the colored bands on the resistor? Also, I'm not questioning here, but the manual says adjust to 5mV +-1mV. Why do you say 3.3mV ? Really appreciate the help.
kevzep
Its all about the Music
They are the square white ceramic resistors....they will have the value written on them it will say 0.33ohmK or something like that.....the K is the tolerance designation which in this case is 5%.....
They are on the F-3093 boards with the output transistors......
The resistors are R-601, and yes you clip onto the resistors legs, with you DMM set to DC mV....and you adjust for 5mV......
Im not actually sure if you can get to the resistors easily, If you can let me know and I will post a picture of where you clip onto the underside of the driver board........
TTomanto123
Member
Wow, that's great OL. Will check this tonight or tomorrow AM. Thanks. -T
OverLoad
High On Solder Fumes
NO, adjust it for 3.3mV's
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