"pipe" capacitors - UK Vintage Radio Repair and Restoration Discussion Forum

Diabolical Artificer · 4th Apr 2011, 2:53 pm

I have quite a few of these in some old amplifiers. I am unable to test their value properly; they are all in the picofarad range, my meter is unreliable under 0.001 farads.

Are they usually reliable or is it best to replace? What's the best bet with old low value caps. (I know about waxies, Hunts etc).

Andy.

G8HQP Dave · 4th Apr 2011, 3:58 pm

They appear to be tubular ceramic capacitors. I think they are usually OK, so leave unless fixing a fault. Most low value caps in a radio will be reliable, and changing them may require some realignment, so best to leave them as they are.

boxdoctor · 5th Apr 2011, 6:18 pm

As G8HQP Dave says, they are tubular ceramic capacitors. Reliability? I think I've probably changed no more than about six in fifty years servicing (excluding the ones in the line deflection circuit in some early TVs which were under great electrical stress). Unlikely to give trouble. Tony

Diabolical Artificer · 5th Apr 2011, 6:28 pm

Thanks both, does anyone know how theyre constructed? I suppose they have been superceded by caps using more modern materials.

Andy.

5th Apr 2011, 7:02 pm

Conductive paint (silver?) over the inside spilling over the end to one connection and more on the outside for the other one.

Graeme Murphy · 8th Apr 2011, 12:55 am

One that I examined a few years ago consisted of a conductor deposited upon the outside surface of the cylinder but with a conductor gap in the centre of the cylinder of one sixteenth of an inch & 360°.
A conformal coating hides this from sight but if you are gentle with the corosil all becomes clear !

Diabolical Artificer · 8th Apr 2011, 1:50 pm

Many thanks for all your help,happy Easter to you all,Andy

4th Apr 2011, 2:53 pm	#1
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,662	"pipe" capacitors I have quite a few of these in some old amplifiers. I am unable to test their value properly; they are all in the picofarad range, my meter is unreliable under 0.001 farads. Are they usually reliable or is it best to replace? What's the best bet with old low value caps. (I know about waxies, Hunts etc). Andy. Attached Thumbnails __________________ Curiosity hasn't killed this cat...so far.

4th Apr 2011, 3:58 pm	#2
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: "pipe" capacitors They appear to be tubular ceramic capacitors. I think they are usually OK, so leave unless fixing a fault. Most low value caps in a radio will be reliable, and changing them may require some realignment, so best to leave them as they are.

5th Apr 2011, 6:18 pm	#3
boxdoctor Rest in Peace Join Date: Sep 2010 Location: Ripley, Derbyshire, UK. Posts: 785	Re: "pipe" capacitors As G8HQP Dave says, they are tubular ceramic capacitors. Reliability? I think I've probably changed no more than about six in fifty years servicing (excluding the ones in the line deflection circuit in some early TVs which were under great electrical stress). Unlikely to give trouble. Tony

5th Apr 2011, 6:28 pm	#4
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,662	Re: "pipe" capacitors Thanks both, does anyone know how theyre constructed? I suppose they have been superceded by caps using more modern materials. Andy. __________________ Curiosity hasn't killed this cat...so far.

5th Apr 2011, 7:02 pm	#5
Guest Guest Posts: n/a	Re: "pipe" capacitors Conductive paint (silver?) over the inside spilling over the end to one connection and more on the outside for the other one.

8th Apr 2011, 12:55 am	#6
Graeme Murphy Tetrode Join Date: Oct 2009 Location: Blyth, Northumberland, UK. Posts: 62	Re: "pipe" capacitors One that I examined a few years ago consisted of a conductor deposited upon the outside surface of the cylinder but with a conductor gap in the centre of the cylinder of one sixteenth of an inch & 360°. A conformal coating hides this from sight but if you are gentle with the corosil all becomes clear !

8th Apr 2011, 1:50 pm	#7
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,662	Re: "pipe" capacitors Many thanks for all your help,happy Easter to you all,Andy __________________ Curiosity hasn't killed this cat...so far.