Referencing the attachment, it is a power supply I hijacked off the internet and plugged in my own parts values, using plain guesswork. I have no training in this and don't want to keep spending money buying parts and wasting time on my own hairbrain plans. What I want is about 230-235 volts of clean DC with 100 milliamps of B+ available. Note also that there is an "unknown resistor" I put in. There's got to be a better way than this trial and error tinkering. Certainly there must be an online calculator or freeware program where I can just enter parts values and get a reasonably usable expectation. Thank you.
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Wow! I can't than you enough. May I ask somebody to check my work on this first time? What I want is about 230V of B+ to run an old tube shortwave radio and about 65ma of B+ current. The first attachment was given to me. What he did was run two 12V transformers back to back for a voltage doubler circuit. I dropped in my choke in in place of the second resistor. I have no idea how to calculate the first resistor because the program doesnt seem to have a way to insert it. How do I calculate that? Simple ohms law, whereas I want to drop 20 volts and there's 65ma of current = 307 ohm, 2 watt resistor.
See my work in this neat new program, attachment 2. Thanks.
See my work in this neat new program, attachment 2. Thanks.
Attachments
At this point, I wouldn't worry about the overvoltage yet. Unless you have the power transformers on hand and have measured their actual resistances, the calculated voltage will only be a good estimate. The final voltage will also depend on your line voltage and actual current drawn by the radio. Build it, measure it, and then calculate the dropping resistor if necessary.
As for the power rating of the dropping resistor, I would use a 3 watt resistor for 1.3 watt power dissipation. It could be hot inside the radio.
As for the power rating of the dropping resistor, I would use a 3 watt resistor for 1.3 watt power dissipation. It could be hot inside the radio.
What I discovered is that this program is pretty nifty, but one thing it doesn't do is provide the correct polarity symbol for polarized capacitors. One thing I've learned is never guess and just connect the negative end to ground. Sometimes the positive end goes to ground. And if you put it in wrong, POW!