- on Audio/Video/Photography
- Published in issue 2/2005 on page 0
Replacement for HT Battery
A 90-volts inverter for vintage radios
Valve circuits and radios in particular are graced by vast crowds of enthusiasts. If you want to keep your prize vintage radio as authentic as possible while actually using it from time to time you need a HV (high voltage) battery or its electronic equivalent.
One of the most popular types of vintage radio running off a high voltage (HV) battery is the valved, portable,medium-wave or long-wave receiver. If you decide to use a switching stepup converter for the 90-volts plate supply then a design using the usual 30-50 kHz switching frequency will soon be found problematic when it comes to preventing harmonics from leaking into the receiver’s RF circuitry. In many cases, the problems are insurmountable.
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.
R1 = 1MOhm5
R2 = 100kOhm
R3,R4,R5,R8 = 100Ohm
R6 = 150Ohm
R7 = 10kOhm
R9 = 680kOhm
C1,C2 = 100nF
C3 = 680nF
C4,C5 = 3300µ F 16V radial (dia. 13mm, 5mm lead pitch)
C6,C7 = 470µ F 200V radial (dia. 25mm, ‘snap-in’; Farnell # 443-7913)
D1 = zener diode 6.2V 0.4W
D2-D7 = 1N4007
T1,T2 = IRLD120 (International Rectifier; Farnell # 362-1066)
IC1 = 74HC04
TR1 = 2x9V 3VA mains transformer
PCB, ref. # 040207-1