Hello and "historic" Power Supply

[schneth3]

Hello
I hope I didn't miss an introduction thread. I'm new here and my name is Tom, living in Switzerland and relaunched my interest in Tube Amplifiers after a break of more than 20y.

In this process I try to understand this published SRPP PreAmp (SRPP-Vorverstärker)

My two question refer to the high voltage power supply shown in pic. 1a

1)
R135, R136 and R137 as TL783 adjustion seem to deliver more than 350V. I would rather more use R135: 10k and R136: 82k .

2)
With R129; 4k7 I would expect around 340V but not 310V.

I'm pretty much sure I missed something, but I don't see the clue. Any ideas?
Thanks
Tom

 

[Ketje]

In this process I try to understand this published SRPP PreAmp (SRPP-Vorverstärker)

My two question refer to the high voltage power supply shown in pic. 1a

1)
R135, R136 and R137 as TL783 adjustion seem to deliver more than 350V. I would rather more use R135: 10k and R136: 82k .

With an average Vref=1,27V the resistors as mentioned in the schematic are allmost right for the 340V.The values you propose are more on the save side.

2)
With R129; 4k7 I would expect around 340V but not 310V.

If there is no current, yes.But if the circuit on terminal 320V draws somewhat like 6mA and the divider, for elevating the heaters, 1mA you loose 7x4k7= ~30V from 340V.
Mona

 

[schneth3]

Hi Mona
Thank's so much! I truely missed the heaters current.