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Marantz 2265B Bias Adjustment

Sergey Green

Sergey Green

Active Member
Hi all,
When adjusting the idle-current, should one channel be positive and the other negative, or should they both be positive? Sounds like a silly question, I know. I set the left channel to 20mV, but the right channel for whatever reason would only allow to go to -20mV. Else it would just sit at 0mV when turned all the way to one end. Is this how it should be, or am I missing something?

The manual simply states - "repeat the same procedure for the other channel", same I would think means 20mV, and not -20mV.

thanks in advance.
-s
 
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+ or - is not important, the pot will allow adjustment from zero and up, it will not reverse the voltage. As long as you read the 20mV, whether it is positive or negative, you're good to go.
 
Another question; will the idle-current setting affect the balance? I mean, if one is different by a small fraction from the other, will that side also sound louder/quieter than the other as well?
 
Do you have a problem where one speaker sounds louder than the other?
Many candidates for this problem like dirty/pitted relay contacts, dirty speaker selector switch/contacts,,,
 
At low volume left channel does come slightly quieter than the right one. At about 15% of the volume knob they both come up to be about equal in loudness (can't say for the tone). I cleaned the pots and switches, as far as I could get to them (also the speaker relay), the left channel comes up immediately, but not as equal (to the right channel) as I would expect it to. What seems odd is that all channels sound about the same after the unit warms up. Or at least it seems that way. I tried every switch and every knob when I observe the divergence, it makes no difference whatsoever. The only knob that makes the/some difference is the tone selector (it comes with the slight click when in the middle), but I suspect it is only the switch to wake something else up. Or, should it be cleaned again?
-s
 
Sergey Green said:
At low volume left channel does come slightly quieter than the right one. At about 15% of the volume knob they both come up to be about equal in loudnes
Click to expand...
It is unfortunately very common that the volume pot tracks poorly (meaning the balance L/R is not right) at the very low volumes (both vintage and modern...)
There is not much you can do about it, except maybe use an attenuator on your sources so that you are using a bigger part of your volume control and not only up to 9 or 10 o'clock as is very common.
 
Hi,

Re-biasing question:

I came across a nice Marantz 2265b and found multiple issues on the P700 board (burnt 300 ohm resistor at R776, a 2k resistor value at R774 where there was supposed to be a 10 ohm, 3 shorted transistors, a blown cap, and one bad output transistor).
I used a DBT to start and noticed that it did not go entirely dim, hence a short. I have all the replacement parts ready to go in. My question is to Re-bias the idle current, do I start with both trim pots counterclockwise, or since the channels are mirrored, one is counter clockwise and the other is clockwise? I just do not want to over bias at start up. I do have a DBT and will be using it. Any help from anyone would be greatly appreciated. I think the trim pots are R716 and R766.

Thanks.

Tony
 
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