R43?

[Thermion]

Shannon,

What is the purpose for R43 in the Ike PS circuit? Just wondering, I'm trying to reduce current flow wherever possible.

JT

[Shannon Parks]

Shannon,

What is the purpose for R43 in the Ike PS circuit? Just wondering, I'm trying to reduce current flow wherever possible.

JT

Hi JT,

This is a good question. The other caps in the power supply are 400V ones in series, giving us a healthy 800V rating. I did this thinking of future designs or experimentation with a higher B+, but also wanted things safe during the tube warm-up phase when the B+ can soar to 550V depending on your mains. Now that I'm discouraging standby switches, this is even more important.

Now R43. I didn't want to use two caps here and didn't need much capacitance. The 450V cap looked perfect, but could see well past its surge ratings during startup. R43, a 470K resistor, is meant as a load to always keep the voltage tamed. It is a simple voltage divider with R30. Even if you raise the voltage for your V1-6SN7 you have less than one mA pass through it. So you definitely want it.

Shannon