11-01-2022, 10:00 PM
Time to try and get back into this project, although success is eluding me for the time being, perhaps time for a bit of a re-think.
I wound a frame transformer using 20 tpv and could just about got the laminations back in. I wound it with a 3:1 ratio, as I was still thinking of EL84 Vales but wound it with a double primary so I could do it as push pull so something wrong in my mind.
It presently has an ECC82 trying a see-saw circuit, I used it OK when I did a low power audio amp with 6021 Valves, but is definitely not working in any way for me now.
The cathode of the ECC82's cathode resister is adjusted to give an Ik of 14 mA, so approx 7mA per section and was hoping with the signal on the grid I could increase the anode current in a half of the valve to peak at say 22mA and shut the other half of the valve off or at least reduce it to 1 or 2 mA, then with the 3:1 ratio have a secondary current of approx 40 plus mA to drive the scan coil and spot to one side but none of it is working. I know the ECC82 is a bit poor on emission, but still thought it capable of better than it is.
Time for a tidy up and think again in the morning or even get out for a walk tomorrow.
Adrian
I wound a frame transformer using 20 tpv and could just about got the laminations back in. I wound it with a 3:1 ratio, as I was still thinking of EL84 Vales but wound it with a double primary so I could do it as push pull so something wrong in my mind.
It presently has an ECC82 trying a see-saw circuit, I used it OK when I did a low power audio amp with 6021 Valves, but is definitely not working in any way for me now.
The cathode of the ECC82's cathode resister is adjusted to give an Ik of 14 mA, so approx 7mA per section and was hoping with the signal on the grid I could increase the anode current in a half of the valve to peak at say 22mA and shut the other half of the valve off or at least reduce it to 1 or 2 mA, then with the 3:1 ratio have a secondary current of approx 40 plus mA to drive the scan coil and spot to one side but none of it is working. I know the ECC82 is a bit poor on emission, but still thought it capable of better than it is.
Time for a tidy up and think again in the morning or even get out for a walk tomorrow.
Adrian
Learning as I go!
Youtube EF91 Valve
Youtube EF91 Valve