Ahuja Amplifier

comasus · 13th May 2011, 12:52 PM

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

Are they for bias or DC offset adjustment?

princenk007 · 13th May 2011, 02:04 PM

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...;-)

khalsa · 13th May 2011, 04:23 PM

hi rp401is bis adjustand rp501is transister temp control

comasus · 06:13 PM

Quote:

Originally Posted by princenk007

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

comasus · 13th May 2011, 06:17 PM

Quote:

Originally Posted by khalsa

hi rp401is bis adjustand rp501is transister temp control

Thanks for your reply

temperature control means?

khalsa · 14th May 2011, 03:43 AM

adjust 1.1v voltage with rp501 on the base 0f Q501 Q502 and heat of output trans is stable this is perfect adjustment

Workhorse · 14th May 2011, 10:54 AM

Comasus,

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

RP501 is bias control for output transistors.

comasus · 14th May 2011, 12:11 PM

Quote:

Originally Posted by Workhorse

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)

Workhorse · 14th May 2011, 02:46 PM

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.

comasus · 15th May 2011, 11:38 AM

Quote:

Originally Posted by Workhorse

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?

14th May 2011, 10:54 AM	#7
Workhorse diyAudio Member Join Date: Dec 2004	Comasus, RP401 is for feedback/gain adjustment for driving the intermediate transformer with proper excitation . RP501 is bias control for output transistors. __________________ It's a fruitless endeavor to try and educate a fool that rejoices in ignorance

14th May 2011, 02:46 PM	#9
Workhorse diyAudio Member Join Date: Dec 2004	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. __________________ It's a fruitless endeavor to try and educate a fool that rejoices in ignorance

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13th May 2011, 02:04 PM	#2
princenk007 diyAudio Member Join Date: Mar 2011 Location: 040	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...;-)

13th May 2011, 04:23 PM	#3
khalsa diyAudio Member Join Date: Dec 2007	hi rp401is bis adjustand rp501is transister temp control

14th May 2011, 03:43 AM	#6
khalsa diyAudio Member Join Date: Dec 2007	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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