Skip to main content

Building a 450VDC Power Supply.

How to design a 450VDC at 0.1-amp Plate Supply for the 12GE5? Copilot jumps in and gives an opinion.




Today
Full wave Bridge power supply: 520 VAC, Choke Input at 10Hy, Filter Cap 100 Microfarad at 500 VDC. Bleeder resistor 10K. Is this OK?

You're working with a pretty serious high-voltage power supply setup, so let's break it down and assess whether it's safe and functional:

⚡ System Overview

  • Input Voltage: 520 VAC (RMS)

  • Rectifier Type: Full-wave bridge

  • Filter Type: Choke input

  • Choke: 10 Henries

  • Capacitor: 100 µF rated at 500 VDC

  • Bleeder Resistor: 10 kΩ

✅ What Looks Good

  • Choke Input Design: This is a classic approach for high-voltage supplies. A 10H choke provides strong filtering and helps maintain continuous current flow, which reduces peak charging currents and improves regulation.

  • Bleeder Resistor: A 10kΩ resistor is reasonable for safety. It will slowly discharge the capacitor when the supply is turned off, helping prevent electric shock.

  • Capacitor Value: 100 µF is a decent size for smoothing ripple in a choke-input filter. It won't overburden the rectifier and will help stabilize the output.

⚠️ Potential Concerns

  • Output Voltage Estimate: With a choke input, the DC output is roughly 0.9 × RMS input. So:

    • 0.9×520 VAC≈468 VDC0.9 \times 520 \text{ VAC} \approx 468 \text{ VDC}

    • Your capacitor is rated at 500 VDC, which gives you only ~7% headroom. That’s tight. If your line voltage spikes or the choke saturates, you could exceed the cap’s rating. Consider upgrading to a 600 VDC-rated capacitor for safety.

  • Bleeder Power Dissipation:

    • At ~470 VDC, the 10kΩ resistor will dissipate:

      • P=V2R=470210000≈22 WP = \frac{V^2}{R} = \frac{470^2}{10000} \approx 22 \text{ W}

    • That’s a lot of heat. You’ll need a high-wattage resistor, ideally 25W or more, possibly mounted with a heatsink.


I will change the Bleeder to 50K and upsize the Voltage Rating on the Filter Cap to 100UFd at 600VDC and this should do the deed. The Panel Meter reads 0 to 500 VDC.


Integrated Power Supply Front Panel

Started work on building the supply and this is what it will look like.


Power Supply for the Hybrid Wireless

In the photo above, along the left side is the 520VCT power transformer and 10 HY choke. The blank PC board will have the Bridge rectifier installed and pad connections for the choke, plus installation of the Filter cap and he Bleeder. That I built yesterday.

Along the right edge is a 12VDC 5.6-amp supply and at the back our 280VDC 0.3-amp supply. 

The Plate Transformer has a 6.3VAC winding which will be used to feed the 12.6 VAC side of a filament transformer rated at 1 amp and pretty small (not installed as yet). This will provide about 60 Volts AC at the terminals normally used for the Primary.

My plan is to add a back panel and mount small filament transformer on that vertical panel and that becomes the Bias Supply at -60 VDC. The Bias Set Pot will be on the Hybrid Wireless Chassis.

The back panel will also contain an 8-pin socket where all of the voltages required by the Hybrid Wireless will be connected.

1. Power Switch
2. Power Switch
3. 450 VDC
4. 280 VDC
5. -60 VDC
6. 12 VDC Filament
7. Ground
8. 12 VDC Relay Supply 




Close up of Bridge Rectifier PC Board
(Parts to be added when they arrive)

A Final Act will be to put some sort of enclosures around any exposed high voltage portion of the circuitry. I have a couple of ideas in mind that will eliminate any potential shock hazards.

Them that know can make things go.

Old what is his name was MIA for a couple of days and has reappeared so to all watchers just a blip on the radar. It is an interesting cultural phenomenon; you are the news even when not making news.

73's
Pete N6QW

Popular posts from this blog

January 26, 2024. A simple CW Transceiver/Transmitter

Cruise through the lower part of the ham bands bands and what do you hear? Well, FT-8 and CW. Often you will not hear any SSB stations yet go to the lower part of the bands, and it is a cacophony (I love that word) of bad sounding signals and some high-speed keying. Fast is not so much of the issue as is bad, run together and jerky keying. But none the less our hobby started there.    So, you could crank down your ICOM 7300 and watch the waterfall on CW or you could homebrew a radio. Actually, to do CW right you need more thought up front than you do with a SSB transceiver. Often, I will state that a CW Transceiver is much more difficult to build than a simple SSB rig. I published two articles in QRP Quarterly on CW transceivers and all I got was a yawn so maybe history will repeat itself.  Yawn!   30M CW Transceiver with RIT!   Of interest is that the LO is a Varactor tuned LC oscillator using a NE602. Look closely at the RIT circuit which is only activated on ...
Read more

March 31, 2024. Happy Easter to those who celebrate this day.

What a great day to Binge on Chocolate and experience the pain of that filling that has been leaking.  I would be in that category with the leaking filling(s) had I not just spent an amount equivalent to one of the fancy new uptown appliance box transceivers on two filling repairs. Well at least I can binge on the Chocolate bunnies without fear of pain. Regrettably everything appears to have jumped in price including the price of parts. Well not so much the parts as the shipping costs.  That notably is seen in the eBay treasures. I spotted a nice heathkit DX-20 for about $50 and the shipping was $65. Likely it is a twofer with part being a way to in effect charge a higher price by inflating the shipping and in part by increased shipping costs. Shipping with insurance across the US was about $150 for this jewel and that was three years ago. 6AM on the Left Coast ~ 20M Easter Sunday! My only hope is the cost of Chocolate Bunnies remains steady although a pound of See's Candies f...
Read more

August 30, 2024. A PNP 20M SSB Transceiver

Shown below is the Block Diagram for the 20M PNP SSB Transceiver steered in the  Transmit Mode . The components shown in the dotted block are relay steered so that the block module is single pass and amplifies in a single direction. The Block diagram show steered in Transmit.  Essentially the steering process works so that the IF Module input follows the Balanced Modulator on Transmit and then the input side follows the Receive Mixer on Receive. All done with some relays and a bit of RG174U coax. For those who count things in detail, this block diagram is not unlike what was used for the PSSST Transceiver which can be found on my website . Yes, a warmed over P3ST only using PNP devices. TYGNYBNT. 73's Pete N6QW
Read more