Hello, i read all treads about this amp, but as am not good at this i have to ask you once again? The amp had a broken minus leg on rca. I replace it and I think everything is working fine, but I think it can soud a little bit better. Amp is in original shape, nothing was repaired. When I power it up on 13,80v it consumes 1,74A. Ehen it is not powered on it consumes 18mA.
My question is can i raise the bias a little and how much?
When i leave it turned on withouth a signal everything is cold but two resistors R150 and R151 which gets hot very soon. IS that normal? They are near little transformer.
I have checked voltage on output transistors and it is the same on all.
Thank you in advance.
My question is can i raise the bias a little and how much?
When i leave it turned on withouth a signal everything is cold but two resistors R150 and R151 which gets hot very soon. IS that normal? They are near little transformer.
I have checked voltage on output transistors and it is the same on all.
Thank you in advance.
Thanks for reply Perry.
I still do not know what do you mean with biased "on"? Is 1.74A enough or low or too much for that amp?
Can you sugest me what to check or what is possible to check if i want to improve sound quality, i mean to returne it to factory settings as close as possible, are there some weak spots on this amps after 20 years which should be changed?
Thank you once again for your time!
I still do not know what do you mean with biased "on"? Is 1.74A enough or low or too much for that amp?
Can you sugest me what to check or what is possible to check if i want to improve sound quality, i mean to returne it to factory settings as close as possible, are there some weak spots on this amps after 20 years which should be changed?
Thank you once again for your time!
The 12v supply current isn't definitive when determining bias without knowing what the idle current is with the transistors biased off (no current flowing through them).
What is the DC voltage with black probe on the wire lead for R97 and the red probe on the 3rd leg of FET6?
DC voltage with black probe on the wire lead of R155 and the red probe on the 3rd leg of FET18?
Do this with no speakers connected and no input signal. Let the amp idle for a few minutes before measuring the voltage. Give the voltage down to the 3rd decimal place. Do not let the probes slip when measuring.
What is the DC voltage with black probe on the wire lead for R97 and the red probe on the 3rd leg of FET6?
DC voltage with black probe on the wire lead of R155 and the red probe on the 3rd leg of FET18?
Do this with no speakers connected and no input signal. Let the amp idle for a few minutes before measuring the voltage. Give the voltage down to the 3rd decimal place. Do not let the probes slip when measuring.
They are probably about right. You could adjust the bias until it's about 0.002 and back to 0.001 to make sure that there isn't an erroneous reading (which can sometimes happen at the edge of the meter's capability). If you do this, make sure that the current draw from the DC power supply doesn't increase significantly.
I put the voltmeter to 200mv section and before I move enything i read 0,6mv. Then i reise the pots till 2,0mv. The current drow from power supply increase to 2,5A. Then I turn it down to 1,1mv and the current drops to 1,98A. I listened for about one hour and I think that the sound become more homogen and natural withouth harsh highs. Amp is warm but i thin it should be like that. After one hour of listening i check again and the bias on both chanels reise to 1,2mv. Do you thin this is ok to leave it like this or I can reise the bias a little more to 1,5mv if it can improve the sound quality more?
Thank you!
Thank you!
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