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:

  • $0.9\times 520\text{ VAC}\approx 468\text{ VDC}0.9\; \backslash times\; 520\; \backslash text\{\; VAC\}\; \backslash approx\; 468\; \backslash text\{\; VDC\}$

  • 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:

    • $P=\frac{V^2}{R}=\frac{{470}^2}{10000}\approx 22\text{ W}P\; =\; \backslash frac\{V^2\}\{R\}\; =\; \backslash frac\{470^2\}\{10000\}\; \backslash approx\; 22\; \backslash text\{\; W\}$

  • 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