Une petite question sur le réglage de bias du 303.
Le manuel spécifie l'utilisation d'un ampèremète pour régler le bias entre 5 et 10mA.
Cf ->
http://www.hifiengine.com/hfe_downloads ... ervice.pdf
Page 6 - paragraphes "Setting Up"
4. Adjust RV101 for 5 to 10mA quiescent collector current measured by breaking the external lead to tag 2 of the left-hand driver board and inserting a meter in series at this point, with no signal drive.
Mais on peut aussi les régler sans dessouder, en mesurant la tension entre les point #4 et #6 des carte drive.
En revanche, personne ne s'est mis d'accord sur la tension idoine à relever.
Ici, c'est 10mV :
http://quadrevisionspot.blogspot.fr/200 ... 3-and.html
In practice you can still measure the DC bias current indirectly by measuring the DC voltage across the emitter resistance of the output transistor.
According to Quad 5-10mA current trough Tr1 of a 303 is enough. But....through R124 flows also the DC current from Tr109 and Tr105. You can measure the DC voltage across R120 and R123 and calculate the current. These currents are 0.8mA and 8.6mA. So the total DC current should be between 14.4 - 19.4mA, giving a DC voltage across R124 of 4.3 - 5.8 mV to meet the Quad specification. More accurate is to measure the voltage across R124 and R125 (leads 4 and 6 on the driver boards). It doubles the value of the voltage (8.6 -11.6mV), but with some voltmeters this give better results. So a good value in practice is 10mV across R124 and R125 (pin 4 and 6 on the driver boards).
ici, c'est entre 3 et 6 mV :
http://tech.groups.yahoo.com/group/quad ... ssage/9785
First warm the 303 up.
Then setup RV200 on the PSU board so that the voltage across pins 1 and 9 on
either amplifier board is exactly 67VDC.
Then, on both amplifier boards in turn, setup RV100 so that the voltage at pin 5
is 33.5VDC.
The official way to set the bias is to disconnect pin 4 or 6 and adjust RV101
for 6-10mA across this broken junction. An easier way is to adjust for 3-6mV
across pins 4 & 6 leaving them in place. In both cases this is with no signal
applied.
The *best* way is to adjust RV101 for minimum crossover distortion using a
distortion analyzer, with a good quality sinewave signal applied and a dummy
load in place. This will probably lead to a slightly higher setting than above.
Pin 1 on the amplifier board has the red wire and they run from right to left
looking down at the component side with the pins farthest away from you. RV100
is in the corner of the board; the position of RV101 varies but it's the other
one.
Ici c'est 7mV :
http://www.dadaelectronics.eu/ForumRetr ... late=False
The idle-current depends on the temperature of the driver-transistors in the first place, indeed. When they warm up the idle current will go up (try blowing on them, you will see the current decrease
I usually set the voltage between pin 4 and 6 to 7 mV, then I wait 10 minutes and I adjust it again.
Alors, qui a raison ?
