Rectifier: Load/Capacitor/Rectifier Current - UK Vintage Radio Repair and Restoration Discussion Forum

ms660 · 24th Oct 2016, 3:10 pm

Found this yesterday (2nd page) might be of interest for some:

http://www.vacuumtubeera.net/HalfWav...plySystems.pdf

Lawrence.

Herald1360 · 25th Oct 2016, 9:31 am

There's an interesting voltage doubler circuit in there with three electrolytics with a common negative terminal. One of them may see a half cycle of reversed voltage though if the supply is turned on at the right point in its cycle.

G6Tanuki · 28th Oct 2016, 9:39 am

I've seen the 3-electrolytics-with-common-negative voltage-doubler used in some US 'midget' type radios. The electrolytic 'block' was usually a cardboard-cased version to avoid issues that would arise if the usual "can negative" can-type electrolytic was clamped to the chassis.

The downside is that neither side of the DC output is common with either of the AC input terminals (unlike the traditional half-wave doubler) which makes providing an earth (ground) connection more tricky. The usual way this seems to be handled in US sets is to use a thick copper wire as a "B-negative" common ground and then only connect this to the radio's actual chassis by way of a low-value capacitor and high-value resistor so the chassis can then be earthed (grounded) in the usual way.

24th Oct 2016, 3:10 pm	#1
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Rectifier: Load/Capacitor/Rectifier Current Found this yesterday (2nd page) might be of interest for some: http://www.vacuumtubeera.net/HalfWav...plySystems.pdf Lawrence.

25th Oct 2016, 9:31 am	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Rectifier: Load/Capacitor/Rectifier Current There's an interesting voltage doubler circuit in there with three electrolytics with a common negative terminal. One of them may see a half cycle of reversed voltage though if the supply is turned on at the right point in its cycle. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

28th Oct 2016, 9:39 am	#3
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: Rectifier: Load/Capacitor/Rectifier Current I've seen the 3-electrolytics-with-common-negative voltage-doubler used in some US 'midget' type radios. The electrolytic 'block' was usually a cardboard-cased version to avoid issues that would arise if the usual "can negative" can-type electrolytic was clamped to the chassis. The downside is that neither side of the DC output is common with either of the AC input terminals (unlike the traditional half-wave doubler) which makes providing an earth (ground) connection more tricky. The usual way this seems to be handled in US sets is to use a thick copper wire as a "B-negative" common ground and then only connect this to the radio's actual chassis by way of a low-value capacitor and high-value resistor so the chassis can then be earthed (grounded) in the usual way.