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Old 9th January 2012, 01:47 PM   #411
AndrewT is offline AndrewT  Scotland
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The output bias and the VAS bias and the LTP bias can all change with changes in supply voltage.

If one tries to set up the output bias via a rail dropping protective resistor, then one must recheck the biases of all stages after removing the protective resistor.
If necessary one must properly bias the stages with the normal Rail voltage applied.

BTW,
some amplifiers go way out of acceptable bias current tolerance when the mains voltage changes.
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Old 9th January 2012, 02:05 PM   #412
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John,

do it as Andrew said.

Remove the resistors across the fuseholders and insert the fuses.
Since you know that your AMP is running, you do not need this resistor any more and you avoid the voltage that drops over this resistor.

Do not connect a speaker to the AMP; short the INPUT (INPUT + = INPUT -).

Switch on the PSU and measure the voltage that drops across the emitter-resistors (0R22).
Depending on the type of output-transistors that you use and the size of your heatsink, adjust the quiescent current so that about 60 - 70mA flows through an emitter resistor, resulting in a voltage drop of about 13 - 15mV over an emitter resistor.
The huge MJL4xxxx transistors can (should) be adjusted to nearly 70mA, a smaller transistor (f.e. NJW0xxx) to 60mA, but this is only my listening impression.


Best regards - Rudi
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Old 19th August 2012, 05:00 PM   #413
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Thumbs up WOW!

wow!.... I haven't seen this pictures looks great the red board is amazing man congratulations Rudi on your nice build bro! " me gusta mucho" "I like it a lot"

Regards
vargasmongo3435

Last edited by vargasmongo3435; 19th August 2012 at 05:11 PM.
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