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Dc offset balance adjustment procedure . Many manuals are not specific
Dc offset balance adjustment procedure . Many manuals are not specific
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Old 12th December 2019, 10:39 PM   #1
Richard_James is offline Richard_James
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Default Dc offset balance adjustment procedure . Many manuals are not specific

I am working on many basic amps
And most manuals don't say which connector is + and which one is -

So you sort of have to guess and search online

Is there a standard convention like positive terminal is mentioned first, negative second

Here is a snapshot of harman 6650r bias adjustment procedure

Which one of them needs to be connected to positive multimeter terminal and which one to negative

Tp407 is definitely negative I think. Black colored cable. 406 and 405 are white and red
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Old 12th December 2019, 10:51 PM   #2
rayma is online now rayma  United States
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The meter polarity doesn't matter for either offset adjustment, or for bias adjustment.
For offset, just connect the meter leads either way and trim to zero.
For output bias, just connect the meter leads either way and trim to the specified magnitude,
ignoring the sign.

Last edited by rayma; 12th December 2019 at 11:13 PM.
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Old 12th December 2019, 11:01 PM   #3
Richard_James is offline Richard_James
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But sometimes adjustments allow for from -10mv to +10mv adjustment

On some nakamichi idle needs to be around 24mv.
And variable resistors can adjust from -20 to +30mv
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Old 12th December 2019, 11:10 PM   #4
rayma is online now rayma  United States
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Quote:
Originally Posted by Richard_James View Post
But sometimes adjustments allow for from -10mv to +10mv adjustment

On some nakamichi idle needs to be around 24mv.
And variable resistors can adjust from -20 to +30mv
Sure, if the specified range is asymmetric, then you need to observe the correct polarity.
The polarity should then be marked on the pcb, by + for example. But the output bias current
can only be in one direction, so just the magnitude is of interest.

Last edited by rayma; 12th December 2019 at 11:15 PM.
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