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Old 13th May 2011, 01:52 PM   #1
comasus is offline comasus  India
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Default Ahuja Amplifier

Could somebody tell me what are those variable resistors for? (RP401 and RP501)

Are they for bias or DC offset adjustment?
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Old 13th May 2011, 03:04 PM   #2
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Yes the same question from me. ....................
I think RP401 is to adjust bias of Q401.....
BTW, How did you acquire schematic brother?

It has the same Circuitry as in Ahuja model 760.....:-) which I have......:-)
In my amp recently, I lost control over Bass. The Bass control on my amp doesn't work at all. There is no bass in the output at speaker.... I am also on fixing the amp...;-)
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Old 13th May 2011, 05:23 PM   #3
khalsa is offline khalsa  India
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hi rp401is bis adjustand rp501is transister temp control
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Old 13th May 2011, 07:10 PM   #4
comasus is offline comasus  India
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Quote:
Originally Posted by princenk007 View Post
Yes the same question from me. ....................
I think RP401 is to adjust bias of Q401.....
BTW, How did you acquire schematic brother?

It has the same Circuitry as in Ahuja model 760.....:-) which I have......:-)
In my amp recently, I lost control over Bass. The Bass control on my amp doesn't work at all. There is no bass in the output at speaker.... I am also on fixing the amp...;-)
This schematic was the last page of the manual given with the amplifier at the time of purchasing (in the year 2000) but now its (ahuja) not providing a schematic

Last edited by comasus; 13th May 2011 at 07:13 PM.
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Old 13th May 2011, 07:17 PM   #5
comasus is offline comasus  India
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Originally Posted by khalsa View Post
hi rp401is bis adjustand rp501is transister temp control
Thanks for your reply

temperature control means?
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Old 14th May 2011, 04:43 AM   #6
khalsa is offline khalsa  India
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adjust 1.1v voltage with rp501 on the base 0f Q501 Q502 and heat of output trans is stable this is perfect adjustment
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Old 14th May 2011, 11:54 AM   #7
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Comasus,

RP401 is for feedback/gain adjustment for driving the intermediate transformer with proper excitation .

RP501 is bias control for output transistors.
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Old 14th May 2011, 01:11 PM   #8
comasus is offline comasus  India
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Originally Posted by Workhorse View Post
Comasus,

RP401 is for feedback/gain adjustment for driving the intermediate transformer with proper excitation .

RP501 is bias control for output transistors.
Thank you for your reply sir

how to adjust these two for good output (no distortion)
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Old 14th May 2011, 03:46 PM   #9
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Keep RP401 at mid position and set the bias thru RP501 till you get 400-450mV at the Base-Emitter junction of output devices Q504/503.
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Old 15th May 2011, 12:38 PM   #10
comasus is offline comasus  India
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Originally Posted by Workhorse View Post
Keep RP401 at mid position and set the bias thru RP501 till you get 400-450mV at the Base-Emitter junction of output devices Q504/503.
Sir

the voltage at base-emitter junction of output transistors is 1.2V when RP501 is minimum
when i put maximum it is increasing up to 2.7V at mid position of RP401

so what must be the biasing voltage?
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