Radial Electrolytic Capacitors - UK Vintage Radio Repair and Restoration Discussion Forum

Diabolical Artificer · 12th Sep 2014, 3:48 pm

Looking through some old copy's of Elektor , circa mid 70's recently, I noticed that all the electrolytic capacitors in the PCB layouts and pictures are exclusively axials.

This got me to wondering if all capacitors were axial and radial capacitors were made after a certain date. Thats's not including big smoothing caps that is.

On the few amps and radios I've worked on so far I can't recollect seeing any radial caps either. Can anyone elucidate?

Andy.

Nickthedentist · 12th Sep 2014, 4:07 pm

Andy,

Radials seem to have gradually ousted axials, probably because they're easier to fit to PCBs using automated machinery than the older, axial design.

From what I've seen, they made their appearance in Far Eastern stuff first, probably in the early 1970s, but that's just speculation.

In modernish catalogues, it's common to see axials marked as "not for use in new designs", presumably becaue manufatcurers plan to discontinue them when demand falls below a certain figure.

N.

Dickie · 12th Sep 2014, 5:50 pm

Radialls were introduced for use on pcbs and take up much less real-estate on the board. In reality axial capacitors are no more difficult to auto-insert than resistors - they can and are/were both supplied in a tape-and-reel format.
Which leads to the question why no radiall resistors? Apart from those ceramic high power ones of course.

matthewhouse · 12th Sep 2014, 6:05 pm

You can buy resistors pre formed into a radial design on reels, most resistors are so small that to make them radial with spaces between the wires would probably make the resistor diameter larger which would be pointless. Axial resistors sitting flat on the PCB don't take up much space, and often have to reach over other tracks anyway.

The only old radial electrolytic capacitors I've ever seen have always been the large reservoir and smoothing chassis mount types. The smaller ones are always axial which suits wired chassis and allows them to sit out the way on pcbs. The new caps are much smaller for the same rating so if they are standing they don't look take up huge amounts of vertical space. unless you use those very long thin types shown recently on that TV PSU.

Restoration73 · 12th Sep 2014, 6:10 pm

Thorn used rectangular radial (carbon) resistors using a striped top colour code in radio and audio from the 60's, and larger types for television - axial (with a folded down leg to make it radial). By comparison, all polystyrene caps seemed to be axial, with radials coming later.

12th Sep 2014, 3:48 pm	#1
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,657	Radial Electrolytic Capacitors Looking through some old copy's of Elektor , circa mid 70's recently, I noticed that all the electrolytic capacitors in the PCB layouts and pictures are exclusively axials. This got me to wondering if all capacitors were axial and radial capacitors were made after a certain date. Thats's not including big smoothing caps that is. On the few amps and radios I've worked on so far I can't recollect seeing any radial caps either. Can anyone elucidate? Andy. __________________ Curiosity hasn't killed this cat...so far.

12th Sep 2014, 4:07 pm	#2
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,841	Re: Radial Electrolytic Capacitors Andy, Radials seem to have gradually ousted axials, probably because they're easier to fit to PCBs using automated machinery than the older, axial design. From what I've seen, they made their appearance in Far Eastern stuff first, probably in the early 1970s, but that's just speculation. In modernish catalogues, it's common to see axials marked as "not for use in new designs", presumably becaue manufatcurers plan to discontinue them when demand falls below a certain figure. N.

12th Sep 2014, 5:50 pm	#3
Dickie Octode Join Date: Sep 2004 Location: St. Albans, Hertfordshire, UK. Posts: 1,478	Re: Radial Electrolytic Capacitors Radialls were introduced for use on pcbs and take up much less real-estate on the board. In reality axial capacitors are no more difficult to auto-insert than resistors - they can and are/were both supplied in a tape-and-reel format. Which leads to the question why no radiall resistors? Apart from those ceramic high power ones of course. __________________ Regards, Richard, BVWS member

12th Sep 2014, 6:05 pm	#4
matthewhouse Octode Join Date: Jul 2006 Location: Willand, Devon, UK. Posts: 1,023	Re: Radial Electrolytic Capacitors You can buy resistors pre formed into a radial design on reels, most resistors are so small that to make them radial with spaces between the wires would probably make the resistor diameter larger which would be pointless. Axial resistors sitting flat on the PCB don't take up much space, and often have to reach over other tracks anyway. The only old radial electrolytic capacitors I've ever seen have always been the large reservoir and smoothing chassis mount types. The smaller ones are always axial which suits wired chassis and allows them to sit out the way on pcbs. The new caps are much smaller for the same rating so if they are standing they don't look take up huge amounts of vertical space. unless you use those very long thin types shown recently on that TV PSU.

12th Sep 2014, 6:10 pm	#5
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: Radial Electrolytic Capacitors Thorn used rectangular radial (carbon) resistors using a striped top colour code in radio and audio from the 60's, and larger types for television - axial (with a folded down leg to make it radial). By comparison, all polystyrene caps seemed to be axial, with radials coming later.