Hi. I have a D-47 build that sounds fanatastic, with the flat 47 capsule and a Funkenwerk transformer. My problem is that I get a to high voltage coming out of the PSU, the lowest I get is 120v. Any advice on how to get it down to about 10v?
How?Adjust the zener diodes and the resitors.
ohms law is your friend.How?
he actually wants to reduce B+ by 10V...If you get 120 V at the point where you should have 10 V, there must be something seriously wrong!
Hi Ruud. I put in a 2k7 resistor and now I am able to dial in 105v. A million thanks.Aah, I see. Well, a resistor is the solution. It depends on the current, usually not more than 1 mA.
I would start with 10 K or 15K and see what the voltage is you get then.
And measure the voltage under load.
By the way: it is not important the get the exact voltage, 1 volt more or less doesn't really matter.
It's a tube, not a computer...
Thanks for great advice, I am now able to dial in the righ volt.Increasing [R3] with the load connected is the best way to dial in the B+. Use a 22k or 47k pot, adjust until you get what you want, then measure the required resistance. Find a fixed resistor that’s close and install that. This marginally improves the filtering too.
But, as Rock says, you need to learn about Ohm’s Law. Pulling current through a resistance causes voltage drop. It’s easy to calculate once you do it a few times. Just don’t forget to add the point and zeros because it’s milliamps, not amps.
When the voltage was 120v the mic had considerable noise, that vanished when the voltage was lowered.More volts on that tube would most likely make it more linear. That extra extra ~8% power dissipated in the plate load resistor from the increased voltage does not hurt.
Capacitors, and other dielectrics will laugh at the difference.
However, if this voltage had somehow changed the cause should be determined.
Hey Greenie, what exactly did you do? Did you replace the resistor at r3 with at 2k7 or did you do something else. My psu seems to have too high a charge as well.Hi Ruud. I put in a 2k7 resistor and now I am able to dial in 105v. A million thanks.
In my case I just put in a 5w 2k7 resistor, peoblem was that the origina<l valu got really warm, and eventually burnt.Hey Greenie, what exactly did you do? Did you replace the resistor at r3 with at 2k7 or did you do something else. My psu seems to have too high a charge as well.
Thanks,
Z
Enter your email address to join: