117L7 valve - UK Vintage Radio Repair and Restoration Discussion Forum

Hunts smoothing bomb · 10th Apr 2014, 8:39 am

Morning all,

I'm going to try and have a stab at building this:-

http://www.antiqueradio.org/transmitter.htm

Does anyone know of a rough equivalent of the pentode section of the 117L7 valve? I know this is an American valve with a 117v heater and also it has very low anode volts compared with the valves over here so I understand it could be slim pickings.

Many thanks

Lee

ValvoStef · 10th Apr 2014, 11:07 am

Hi lee

I looked at this a while ago as well, did some research and came across a suggestion to use ECC83 and EL84 and adapt the voltages accordingly. However, this is a powerful transmitter and might not be legal here in the UK, I think 10 mW and below is allowed.

BR

turretslug · 10th Apr 2014, 11:20 am

I, too, am a little worried about using either the 117L7 (described as "beam power tetrode and rectifier") or an EL84 as a local (sometimes "pantry") transmitter- you might end up with a stern knock on the door... An EF91 or EF80 might be more prudent, or I'm sure there has been discussion of the EH90 here and elsewhere- the EH90 sounds like both a hygenic and low-power way of doing things.

paulsherwin · 10th Apr 2014, 11:27 am

The 117L7 is basically a UL84 and UY85 in a single envelope with a 117V heater, allowing it to be used in a cheap record player without a transformer or dropper (in 110V countries anyway). You can use just about anything in place of the pentode section in the Lil'7 design because it's just an oscillator.

As has been said, this design is illegal in the EU, and probably in the US too, so if you build it make sure that the signal isn't leaking out. Increasing the HT voltage will increase the output even further.

Hunts smoothing bomb · 10th Apr 2014, 2:24 pm

Hi guys, thanks for the replies.
I will try an EF183/184 or EF80 or something and lower the HT volts I think to get signal just within the house.

Cheers
Lee

paulsherwin · 10th Apr 2014, 2:29 pm

You can also adjust the aerial to reduce the range.

FrankB · 10th Apr 2014, 7:16 pm

I have repaired many old record players and a few table radios that used the 117L7.
I am just paranoid enough I always use an isolation transformer on any equipment like that.
They do work quite well, and I have access to many 117L7's, as they are pretty common to find here.

kentplums · 29th Jul 2016, 5:13 pm

Hi all, especially FrankB... if you still have a few of those tubes lying around I would be more than interested - tell me more. I'd be running on European 230v so a step down tx would have to be used .

Resurrection of an old post I realise

cheers
R

FERNSEH · 29th Jul 2016, 9:43 pm

Check out this application for the 117L7. Interesting zero anode volts oscillator.
http://www.radiomuseum.org/tubes/tube_117l7.html

DFWB.

kalee20 · 30th Jul 2016, 11:08 pm

I'm not sure about that - I reckon there's about half a volt to run the oscillator, generated by contact potential in the rectifier section.

Interesting circuit though!

FrankB · 12th Sep 2016, 7:23 am

Kent,
Just saw your post. I do have some here as spares. When I get them dug out, I'll let you know. Feel free to bug me from time to time on them too. My memory is not what it used to be.

10th Apr 2014, 8:39 am	#1
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,407	117L7 valve Morning all, I'm going to try and have a stab at building this:- http://www.antiqueradio.org/transmitter.htm Does anyone know of a rough equivalent of the pentode section of the 117L7 valve? I know this is an American valve with a 117v heater and also it has very low anode volts compared with the valves over here so I understand it could be slim pickings. Many thanks Lee __________________ Lee

10th Apr 2014, 11:07 am	#2
ValvoStef Hexode Join Date: Mar 2014 Location: Fareham, Hampshire, UK. Posts: 482	Re: 117L7 valve Hi lee I looked at this a while ago as well, did some research and came across a suggestion to use ECC83 and EL84 and adapt the voltages accordingly. However, this is a powerful transmitter and might not be legal here in the UK, I think 10 mW and below is allowed. BR __________________ Failing to prepare is preparing to fail ...

10th Apr 2014, 11:20 am	#3
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,396	Re: 117L7 valve I, too, am a little worried about using either the 117L7 (described as "beam power tetrode and rectifier") or an EL84 as a local (sometimes "pantry") transmitter- you might end up with a stern knock on the door... An EF91 or EF80 might be more prudent, or I'm sure there has been discussion of the EH90 here and elsewhere- the EH90 sounds like both a hygenic and low-power way of doing things.

10th Apr 2014, 11:27 am	#4
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: 117L7 valve The 117L7 is basically a UL84 and UY85 in a single envelope with a 117V heater, allowing it to be used in a cheap record player without a transformer or dropper (in 110V countries anyway). You can use just about anything in place of the pentode section in the Lil'7 design because it's just an oscillator. As has been said, this design is illegal in the EU, and probably in the US too, so if you build it make sure that the signal isn't leaking out. Increasing the HT voltage will increase the output even further.

10th Apr 2014, 2:24 pm	#5
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,407	Re: 117L7 valve Hi guys, thanks for the replies. I will try an EF183/184 or EF80 or something and lower the HT volts I think to get signal just within the house. Cheers Lee __________________ Lee

10th Apr 2014, 2:29 pm	#6
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: 117L7 valve You can also adjust the aerial to reduce the range.

10th Apr 2014, 7:16 pm	#7
FrankB Heptode Join Date: Oct 2005 Location: Olympia, Washington, USA. Posts: 664	Re: 117L7 valve I have repaired many old record players and a few table radios that used the 117L7. I am just paranoid enough I always use an isolation transformer on any equipment like that. They do work quite well, and I have access to many 117L7's, as they are pretty common to find here.

29th Jul 2016, 5:13 pm	#8
kentplums Hexode Join Date: Nov 2012 Location: Limoges, Haute-Vienne, France. Posts: 280	Re: 117L7 valve Hi all, especially FrankB... if you still have a few of those tubes lying around I would be more than interested - tell me more. I'd be running on European 230v so a step down tx would have to be used . Resurrection of an old post I realise cheers R

29th Jul 2016, 9:43 pm	#9
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: 117L7 valve Check out this application for the 117L7. Interesting zero anode volts oscillator. http://www.radiomuseum.org/tubes/tube_117l7.html DFWB.

30th Jul 2016, 11:08 pm	#10
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,082	Re: 117L7 valve I'm not sure about that - I reckon there's about half a volt to run the oscillator, generated by contact potential in the rectifier section. Interesting circuit though!

12th Sep 2016, 7:23 am	#11
FrankB Heptode Join Date: Oct 2005 Location: Olympia, Washington, USA. Posts: 664	Re: 117L7 valve Kent, Just saw your post. I do have some here as spares. When I get them dug out, I'll let you know. Feel free to bug me from time to time on them too. My memory is not what it used to be.