Ton Giesberts
About the article

High Voltage Supply

or the Valved RIAA Preamplifier and other applications330 V from 12 V

High Voltage Supply
Although this supply was primarily designed for use with the Valved RIAA Preamplifier, we found that the inverter stage is useful in many other applications. With only a small modification this circuit can be used to power a 20 W PLCE (low energy) lamp from a 12 V car battery.The Valved RIAA Preamplifier uses two valves, just like the Valve Preamplifier that was published in the June 2000 edition of Elektor Electronics. Since the valves’ filaments have again been connected in series, the preamplifier requires two DC supply voltages: 12.6 V for the filaments and 330 V for the high voltage supply.In order to avoid the need to use a custom transformer the circuit has been designed to use a standard 15 V/3 A mains transformer. As we’ll see later, the supply circuit consists of two distinct sections: a conventional 12.6 V filament supply and a step-up converter which boosts the 12.6 V to 330 V. In other words, the filament supply is also used to power the inverter.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list
12.6 V Supply
R1 = 1.2 k-ohm
R2 = 6.8 k-ohm
C1 = 10µ F 63V radial
C2,C3 = 100nF
C4,C5,C6 = 2200µ F 25V radial
C7-C10 = 47n F ceramic
D1 = 1N4148
D2 = red high-efficiency LED
D3-D6 = FR606 (or similar 6A diode)
IC1 = KA78T12 (3A)
K1,K2,K3 = 2-way PCB terminal block, lead pitch 5mm
For IC1: heatsink type SK129 63,5 STS, 3.5 K/W (Fischer) (Dau Components)
Isolation material for IC1
PCB, order code 000186-2
330-V converter
R1,R2 = 120 k-ohm
R3 = 4.7 k-ohm
R4 = 470 k-ohm
R5 = 1 k-ohm
R6 = 15 k-ohm
R7 = 6.8 k-ohm
R8,R9 = 680 k-ohm
R10 = 330 k-ohm
R11,R12,R13 = 2.2 ohm
R14 = 100 ohm
R15,R16 = 82 k-ohm
P1 = 100 k-ohm preset H
P2 = 10 k-ohm preset H
C1 = 1nF ceramic, lead pitch 5mm
C2,C9 = 10nF ceramic, lead pitch 5mm
C3,C7,C10 = 100nF ceramic, lead pitch 5mm
C4 = 1nF MKT, lead pitch 5mm
C5,C6 = 100µF 16V radial
C8 = 100µF 25 V radial
C11 = 220µF 25V radial
C12 = 4nF7
C13,C14,C15 = 2µF2 450V radial, lead pitch 5mm, diameter 10mm
C16,C17,C18 = 1000µF 25V radial
L1 = suppressor coil 40µH 3A, type SFT10-30 (TDK)
L2,L3 = 47mH, e.g., 2200R series type 22R476 (Newport Components)
D1-D4 = BY329-1000 (Philips)
D5 = BAT85
T1 = BC550C
T2,T3 = BUZ11
IC1 = SG3525A(N) (ST Microelectronics)
K1 = 2-way PCB terminal block, lead pitch 5mm
K2,K3 = 2-way PCB terminal block, lead pitch 7.5mm
F1 = fuse 2AT (time lag) with PCB mount holder
TR1 = ETD29 (Block)
primary: 2 windings 11 x (3 x 0.5 mm parallel) ecw
secondary: 1 winding 300 x 0.3 mm ecw
PCB, order code 000186-1
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