Updated 10/29/2023: This page presents series of links and articles regarding power supply construction, safety and other aspects. Please return often as I add more content. Note that I am not an engineer – these are mostly references that I thought were useful and some things I’ve done in the past.
Fusing the HV supply (a Littlefuse “white paper”)
Soft Start Ideas for HV Transformers
Soft Start – Step-start; Inrush Current (by W8JI)
Choke Input and Capacitor Input power supplies (by W8JI)
An “Economy” three-voltage power supply by W8JI. On this document, scroll down to the “Full Wave Bridge with Choke” section. The schematic there illustrates the use of a 500-0-500 volt transformer.
The schematic can be reconfigured to generate 2800V (voltage doubler, capacitor input filter), 1400V (capacitor input, full wave), 900V (choke input full wave). In each case, a second voltage of 1400, 700 or 450 volts (i.e., half the full B+ voltage) can also be obtained. R1 feeds the highest HV load, R2 feeds the lower HV load and R3 provides a bias voltage.
Remember that, if a voltage doubler is used, the milliamp capacity of the transformer must be halved since the wattage capability of the transformer remains unchanged no matter what we do to its output voltage.
Older versions of the ARRL Handbook will also have an illustration and explanation of an “Economy Power Supply.”
Balancing (equalizing) resistors for a capacitor bank
This article explains how to properly size the resistors used to equalize the voltage across each electrolytic filter capacitor and how to determine what wattage these resistors should be, when two or more electrolytic capacitors are used in series in the power supply.
To the article I would add a reminder that these equalizing resistors are NOT meant to be a bleeder resistor system although some will use them as such. They WILL, however, draw some current from the B+ line and this should be taken into consideration when figuring how much current the equalizer system and the real bleeder should be asked to handle.
A separate “bleeder” resistor, from B+ to ground should be incorporated. This is sometimes called a “safety bleeder.” Even if one of the equalizers fails open, stopping the current draw of that resistor string, the safety bleeder will continue to bleed a small amount of current, and will discharge the filter capacitors when the B+ is turned off. Otherwise the filters will not be discharged for a very long time, which is a safety problem.
Be sure the safety bleeder is properly sized, both in ohms and wattage to not fail if one of the equalizers fails open and the B+ rises somewhat. Also, be sure to prevent the B+ from arcing across it (perhaps using several in series).
For example, the safety bleeder in my junkbox-built 2800 V supply consists of 5, 100K, 5 Watt wirewound ceramic resistors in series. This provides just under 3 ma of current to slowly discharge the electrolytics should the equalizer string fail open. The ohm value to use will vary depending on the amount of high voltage present and how fast a bleed-down is desired. 5 ma is probably a better target but I used what I had. In my case, by the time I remove the screws holding the lid of the case, the 3 ma bleed has just about fully discharged the capacitor bank.
And finally, be sure to measure the equalizer and bleeder resistors with an ohm meter before installing them. When constructing my HV supply, I found that one of the new resistors marked 20K was actually 165K. It might have failed due to heat overload and would certainly have upset the current draw through the string.
Metering an Amplifier (by W8JI)
Multi-Low-Voltage Power Supply for Workbench
Repairing Linear Low-voltage Power Supplies (especially Astons) and circuits to build your own.
QEX Power Supply Article (very complex supply)
High Voltage Power Supplies – Input Chokes, etc
Here is a good zener diode tutorial by Eliott Sound Labs. In addition to the tutorial, it provides a useful table of zener identifying numbers, their characteristics and parameters.
Zeners are noisy things; typically a disc ceramic capacitor mounted as close as possible to the Zener, and parallel to it, is good noise-reduction practice. This link provides good examples of simple noise reduction techniques, using an LM317 regulator as a test bed.
7800 Regulator Series; examples, create
Variable Voltage Supplies, etc. See also the Zener diode information above.
Power Supply Design for Vacuum Tube Amplifiers presents an in-depth tutorial regarding the subject.