Can someone Help me with this, I use EasyEda to build this. But it does not work, and I don't know why can someone tell me where is my mistake?
I can't bias the amp. The bias point jump from 0.4V to 8-12V and the Tube Become a more like a light bulb, There is no sound, The antipop relay delay circuit that is there is for DC protection, it works fine, it is switching as it should.
I can't bias the amp. The bias point jump from 0.4V to 8-12V and the Tube Become a more like a light bulb, There is no sound, The antipop relay delay circuit that is there is for DC protection, it works fine, it is switching as it should.
If I read the schematic right the 12au7 only has 12Vdc across it. I’m not sure the tubes are going to like that resulting in distortion. 120V maybe?
Can that 12V 0.5A reg provide enough current? It could even be that the 15V DC power supply (DC In) is underrated...
I'd use a separate 12V reg just for the heater.
... assuming there are no mistakes in the PCB layout...
I'd use a separate 12V reg just for the heater.
... assuming there are no mistakes in the PCB layout...
The heater need 150mA when the two heaters are connected in series, The constant current source is set to draw 125mA, So
150mA heater
125mA Righ Ch
125mA Left Ch
Total current need of the circuit is 400mA
The 78XX can give 1A
The PS is 15V 2A. The regulator dissipation is 15V-12V=3V, so 3V x 0.4A = 1.2W. The Regulator can dissipate 1.2W with a small Heatsink. The Regulator is not getting hot. So the circuit is not drawing current.
I tested this bypassing the regulator and connecting a 12V 1A supply directly and it was the same. I don't know, I will better build another circuit, I already own a Pmillet starving student amp which work with the same principle but using the heater as the current source.
Are you still working on this or already given up?
Where is the bias point on your schematic, where do you measure that?
Did you export the schematic to the PCB layout or did you do the PCB layout 'by heart'?
Jan
Where is the bias point on your schematic, where do you measure that?
Did you export the schematic to the PCB layout or did you do the PCB layout 'by heart'?
Jan
Hi, I still have 4 good new PCBs, The bias point is marked with a 6V tag in the schematic and there are bias test point in the PCB. The schematic was exported using EasyEDA so there are no error going from schematic to layout.
Maybe a pinout issue with the potentiometer? You might try removing them and replacing with fixed 4.7k resistors to start.