Not clear from the pic, is the Transformer hanging from one side or it is locked from both ends???
When i rebuild my F6 recently, i turn the Bias 5K pot to zero, checking with a multimeter.
And Offset pot somewhere between 25~50% of the 5K pot range.
When i first power-up, there is no current flow through the 0.47R resistor, then i start turning up the Bias pot, and current creeps up slowly.
Bias and offset are somehow interrelated during adjustments, so i suggest you use 2 multimeter at the same time during adjustments.
Good luck with your F6!
And Offset pot somewhere between 25~50% of the 5K pot range.
When i first power-up, there is no current flow through the 0.47R resistor, then i start turning up the Bias pot, and current creeps up slowly.
Bias and offset are somehow interrelated during adjustments, so i suggest you use 2 multimeter at the same time during adjustments.
Good luck with your F6!
After experiment with different bias level, i settled for 1.65A @55DegC.
I did try 1.8A but the heatsinks temp went above 60DegC, personally i feel uncomfortable, not that it will fail, just too hot for me to feel safe in a home environment.
Maybe i should use a bigger chassis with larger HS.
Currently on Conrad 350x151x50.
This F6 is quiet, even though sharing same SLB ps for both channels, which surprises me as not much to do to troubleshoot ground looping hums and noises.
How much DC on the F6 input is too much?
Bel Canto recommends in the DAC3 user manual that the balanced outputs should be used, if possible, due to a slight DC offset on the single-ended outputs. Indeed I measure about 4mV of DC on the single-ended outputs.
So, my question to the experts on this forum: Given that the F6 appears to be direct coupled to the Jensen transformer via the JFETs (no DC blocking capacitor), should I worry about 4mV DC causing magnetization of the Jensen transformer?
Bel Canto recommends in the DAC3 user manual that the balanced outputs should be used, if possible, due to a slight DC offset on the single-ended outputs. Indeed I measure about 4mV of DC on the single-ended outputs.
So, my question to the experts on this forum: Given that the F6 appears to be direct coupled to the Jensen transformer via the JFETs (no DC blocking capacitor), should I worry about 4mV DC causing magnetization of the Jensen transformer?
Anyone out there please feel free to correct me if the following concept or math is wrong:
Papa's F6 lecture says there is about a 25 ohm source impedance at the Jensen transformer input. Ohms law says that 0.004 VDC divided by 25 ohms = .16 mA of DC flowing in the core. Now, the core is already sinking the Idss of the inputs through an 18 ohm resistor, about 1 mA or so for 8 mA Idss devices, but it's a hefty core and should not even blink at so little DC. An extra tenth of a mA or so should not be an issue.
4th of July...Firework! All is good now
Early 4th in the morning, I powered on my F6 for the first time. Firework! I put a fast blowing 1a fuse. It was blown a part with a big flash. How could it be? After hours of agonizing retracing I've found the cause. Alas! I reversed the power transformer. Complete complacency in my part.
I finally finished my F6. I can not say that I've built it. It was more like I put it together for someone else did most of the work for me. The board was exellent, 6l6's build guide was awesome! And I am so grateful that avdesignguru and 6l6 wisely pointed to the Deluxe 4U Steel. It was a game changer for me. Without it, it could have been hard and agonizing journey.
So, it has been baking in the last 30 mins or so. The 4th is over and no firework. The chassis is warm but not hot. My BBQ grill thermometer says that it is not hot enought to grill as it reads 44C to 45C. So it is not burning. The bias is set at .502V and the offset is at 0+/- 0.03. I am good for now.
I can't listen to it as my preamp is down. But B1 pre board is arriving today. Hopefully, I will be done in "putting together" the kit this week. Perhaps I could listen to these beauties by this weekend. I will report then. Thanks everybody. It has been a challenging year for me. This project helped me to destress.
Early 4th in the morning, I powered on my F6 for the first time. Firework! I put a fast blowing 1a fuse. It was blown a part with a big flash. How could it be? After hours of agonizing retracing I've found the cause. Alas! I reversed the power transformer. Complete complacency in my part.
I finally finished my F6. I can not say that I've built it. It was more like I put it together for someone else did most of the work for me. The board was exellent, 6l6's build guide was awesome! And I am so grateful that avdesignguru and 6l6 wisely pointed to the Deluxe 4U Steel. It was a game changer for me. Without it, it could have been hard and agonizing journey.
So, it has been baking in the last 30 mins or so. The 4th is over and no firework. The chassis is warm but not hot. My BBQ grill thermometer says that it is not hot enought to grill as it reads 44C to 45C. So it is not burning. The bias is set at .502V and the offset is at 0+/- 0.03. I am good for now.
I can't listen to it as my preamp is down. But B1 pre board is arriving today. Hopefully, I will be done in "putting together" the kit this week. Perhaps I could listen to these beauties by this weekend. I will report then. Thanks everybody. It has been a challenging year for me. This project helped me to destress.
