Use for all those worn out UL41s? - UK Vintage Radio Repair and Restoration Discussion Forum

Biggles · 17th Oct 2014, 9:49 pm

Don't throw those old low emission valves away. Why not use them as droppers in series heater chains? Obviously you will need to work out the correct current and voltage drop for your particular application. I thought this would be well suited to home brew equipment, saving the cost and mounting problems associated with modern power resistors. It retains the period look too if you use an extra chassis mount valve base for the "dropper"
Alan.

Radio Wrangler · 17th Oct 2014, 11:25 pm

Might be a problem with inrush current as the heaters start out low resistance and you're reducing the proportion of stable resistance.

David

turretslug · 18th Oct 2014, 6:16 am

I guess they'll continue "heating" for quite some time after their primary function has given out- possibly for some low-power background application such as propogators?

Mind you there's the fragility and eventual reliability question here, "gold block" metal-clad power resistors aren't a fortune especially from surplus etc. sources. Yes, it's difficult to think of a useful secondary employment for them...

PJL · 18th Oct 2014, 9:00 am

Alternatively, send the UL41's to me and I'll get them working again.

kalee20 · 18th Oct 2014, 11:47 am

Quote:

Originally Posted by Radio Wrangler

Might be a problem with inrush current as the heaters start out low resistance and you're reducing the proportion of stable resistance.

Yes - though it's no worse for the valves than if they were operated from a transformer. Might hurt a series-connected pilot lamp though.

Must say I'd go for the gold aluminium-clad resistors as turretslug says, it's less chassis drilling. But if you are using breadboard construction, then yes, use the heaters of otherwise-dead valves.

ionburn · 21st Dec 2014, 9:18 pm

Maybe a step too far but bottles that still light may still find value as otherwise operational looking valves for display purposes. I know that some like their displays and what better than a 'lit up' chassis!

FrankB · 17th Jan 2015, 4:36 am

In a few radios here I saw defective tubes having the elements tied together and being used as rectifiers. This was done here mostly during the war, as tubes were quite scarce.
they had to modify the socket accordingly, of course.

17th Oct 2014, 9:49 pm	#1
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Use for all those worn out UL41s? Don't throw those old low emission valves away. Why not use them as droppers in series heater chains? Obviously you will need to work out the correct current and voltage drop for your particular application. I thought this would be well suited to home brew equipment, saving the cost and mounting problems associated with modern power resistors. It retains the period look too if you use an extra chassis mount valve base for the "dropper" Alan.

17th Oct 2014, 11:25 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,902	Re: Use for all those worn out UL41s? Might be a problem with inrush current as the heaters start out low resistance and you're reducing the proportion of stable resistance. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

18th Oct 2014, 6:16 am	#3
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,400	Re: Use for all those worn out UL41s? I guess they'll continue "heating" for quite some time after their primary function has given out- possibly for some low-power background application such as propogators? Mind you there's the fragility and eventual reliability question here, "gold block" metal-clad power resistors aren't a fortune especially from surplus etc. sources. Yes, it's difficult to think of a useful secondary employment for them...

18th Oct 2014, 9:00 am	#4
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Use for all those worn out UL41s? Alternatively, send the UL41's to me and I'll get them working again.

21st Dec 2014, 9:18 pm	#6
ionburn Heptode Join Date: Dec 2014 Location: Lincoln, Lincolnshire, UK. Posts: 583	Re: Use for all those worn out UL41s? Maybe a step too far but bottles that still light may still find value as otherwise operational looking valves for display purposes. I know that some like their displays and what better than a 'lit up' chassis!

17th Jan 2015, 4:36 am	#7
FrankB Heptode Join Date: Oct 2005 Location: Olympia, Washington, USA. Posts: 664	Re: Use for all those worn out UL41s? In a few radios here I saw defective tubes having the elements tied together and being used as rectifiers. This was done here mostly during the war, as tubes were quite scarce. they had to modify the socket accordingly, of course.