SSLV1.1 builds & fairy tales

[amandarae]

Thank you Salas (Nick!).
Another question for the transformer in your example. AS-0532 is the minimum to use for bipolar 30Vdc regulated output?
I thought 28Vac rectified is about 39.5 Vdc and should be enough?

 

[Salas]

It depends on how high the Tx goes at this load. Its less than x1.41 DC due to bridge Vf and ripple losses but its also more than nominal AC due to less than nominal secondary current load. 28V Tx could work well but I said 32V just to make sure. Even if mains are low in a place.

 

[amandarae]

Thank you Salas!

 

[merlin el mago]

Salas I don't know if it's answered but I'm looking to know R303 value for 6.3Vout?

I guess something between 220R & 1K8 right?

 

[Salas]

For 6.3V voltage region, use R103(303) jumper D101(301) Jumper Trimmer R105(305) 1k

 

[merlin el mago]

I don't understand you well, all voltatge reference area with jumpers excepte R103(303) 1k?

 

[Salas]

2 red Leds no Zener no R (jumpers in their places) just 1k trimmer

 

[merlin el mago]

Thank you.

 

[merlin el mago]

What's your best reg. to use for grid bias isn't for high voltage it's for 7N7 or 5687 tubes so a maximum of -10V and minimum -2V could be ok , also what's better to use the negative or the positive version of the reg.?

TIA
Felipe

 

[Salas]

Negative section of course but -2.5V minimum with BJT output option. Nevertheless using a shunt reg for negative grid bias seems overkill. Did you try using a battery first?

 

[merlin el mago]

Yes. Attached pic of 7N7 with grid battery bias and schematic used.

 

[Salas]

Aren't you happy with stability of bias and low noise level by using the battery?

 

[Salas]

*Battery is floating and its isolation is a better bet for achieving low noise than to put some mains fed and earth referenced electronic PSU directly to the control grid.

 

[merlin el mago]

Can't reach the bias I want: 9mA 150V at anode -3V grid. As you can see I use Ale Moglia hibryd mu-follower as anode load. If I set the hibryd mu-follower to 150V at plate the current increase till 15mA.

 

[merlin el mago]

What do you think of schematic used for battery, some people connect the battery between the 1Meg grid leak resistor and ground?

 

[Salas]

Who made that schematic uses the battery as a coupling capacitor as well I would think.

 

[Salas]

Can't reach the bias I want: 9mA 150V at anode -3V grid. As you can see I use Ale Moglia hibryd mu-follower as anode load. If I set the hibryd mu-follower to 150V at plate the current increase till 15mA.

CCS on plate sets mA bias fighting with fixed negative grid bias maybe.

 

[Salas]

The original schematic had a plate resistor, yes?

 

[merlin el mago]

Yes.

 

[merlin el mago]

What happens Salas: Gyrators, CCS, hibryd mu-followers so active loads doesn't work well with battery bias?