Moderators: pompeiisneaks, Colossal
This is the sag resistor that emulates the effect that a tube rectifier has. It has to be pretty big because of the voltage at this location.harryk wrote:Hi Humbucer! Do you have any idea why the wattage in rail voltage B1 resistor 1kohm is 25W?
We answered that question some time ago but I'm not sure what thread. From what I remember about the calculations the resistor wattage needed was at least 10 watts and since that would have run a little hot the next size up would be a 25 watt. As far as sag goes 1k would be kind of a large value for sag resistors and they are usually placed in the current path immediately after the recto and before the Plates of the power tubes. They usually run 10 - 500 ohms for sag resistors. The 1k 25w resistor is used to keep the screen supply at some voltage 10-20 volts less than the plates.gtrcollectr wrote:This is the sag resistor that emulates the effect that a tube rectifier has. It has to be pretty big because of the voltage at this location.harryk wrote:
Todd
I just finished my Liverpool project without cabin. There are some minor tweakings and adjustments left but I got possibility to test my first Twreck amp ever in real life. I have 4,7 kohm/5W resistor between B1 and B2 instead of that 1 kohm/25W and it seems to be ok for that purpose. My PA voltages are higher than in original due to 2x300VPT. I have EL84 tubes plates 367V and screens 326V. Rail voltages from B2 to B5 are near original. After a short test I have to say that this will not be my last effort with Twrecks. Sound is so dynamic, open and harmonic compared to many other tube amps. Thanks to everybody supporting and helping me with my first Twreck project. Regards HarryCongrats on the new build!!harryk wrote:
