Hello
I'm stucked again. Building Poindexter's 6V6Gt push Pull amp.
Everything is finished, power supply seems to work, but no sound out from the amp.
Here is the schematic. I have 267 volt DC at the plate of 6v6 PP which is lower than the 315 volt specified. But 6v6gt specsheet specify 285 volt in push-pull triode configuration. Am i within specs?
Bias circuit seems OK, voltages are close.
5965 driver circuit is also low in voltage, 255 volts at point B instead of 295 volt specified, but the driver triodes seems to work, I measure signal at the 6V6 grid, approximately 10X higher voltage than the input. But still no sound.
Thanks for any help guys.
F
I'm stucked again. Building Poindexter's 6V6Gt push Pull amp.
Everything is finished, power supply seems to work, but no sound out from the amp.
Here is the schematic. I have 267 volt DC at the plate of 6v6 PP which is lower than the 315 volt specified. But 6v6gt specsheet specify 285 volt in push-pull triode configuration. Am i within specs?
Bias circuit seems OK, voltages are close.
5965 driver circuit is also low in voltage, 255 volts at point B instead of 295 volt specified, but the driver triodes seems to work, I measure signal at the 6V6 grid, approximately 10X higher voltage than the input. But still no sound.
Thanks for any help guys.
F
Attachments
If I put input signal on the input of the amp (0,3 volt approx), I get approximately 10 volt AC on the primary wires of the output transfo. So in theory, I should get some signal out I guess.
Output trans are hammond 1608. Here is the input schematic from manufacturer:
I connected the blue and brown to 6v6 plates, and red is 267 volt DC. The SG taps are not connected to anything right now.
F
Output trans are hammond 1608. Here is the input schematic from manufacturer:
I connected the blue and brown to 6v6 plates, and red is 267 volt DC. The SG taps are not connected to anything right now.
F
Attachments
Hi Gary,
Your hookups are correct according to the Hammond catalog. You could ground, or not. There is no feedback to worry about. You should be getting something.
Do you have an oscilloscope handy? The circuit may be oscillating ultrasonically. I'd still expect some noise though.
Do me a favour and do the above test to make sure the output and speaker connections are okay.
-Chris
Your hookups are correct according to the Hammond catalog. You could ground, or not. There is no feedback to worry about. You should be getting something.
Do you have an oscilloscope handy? The circuit may be oscillating ultrasonically. I'd still expect some noise though.
Do me a favour and do the above test to make sure the output and speaker connections are okay.
-Chris
I can have an oscilloscope, but don't have it today. I will make the test later today or in teh next few days. Thanks for the info.
Also, the power supply caps discharge quite quickly when i put the power off. All the voltages are down to zero in maybe 10 seconds when tubes are in.
Is this normal?
F
Also, the power supply caps discharge quite quickly when i put the power off. All the voltages are down to zero in maybe 10 seconds when tubes are in.
Is this normal?
F
Duh!
hehe
I found a big mistake. The output banana connectors were shorting with the frame. So no output of course....
I fixed that and the amp work well right now. Distorsion is present a medium volume, but I need to adjust supply voltages set bias correctly. Otherwise, sound is real nice!
I guess I needed to sleep on this one to find that stupid mistake... Thanks again for the help
F
hehe
I found a big mistake. The output banana connectors were shorting with the frame. So no output of course....
I fixed that and the amp work well right now. Distorsion is present a medium volume, but I need to adjust supply voltages set bias correctly. Otherwise, sound is real nice!
I guess I needed to sleep on this one to find that stupid mistake... Thanks again for the help
F
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