Battery valve output transformer - UK Vintage Radio Repair and Restoration Discussion Forum

Mike Brett · 3rd Jan 2014, 1:48 pm

Hi all
I am building a small battery valve amplifier that uses a DAF91 and a DL92. I intended to use a small speaker along with a small output transformer that was salvaged from an old radiogram chassis. I was just wondering if this output transformer would be suitable or not, and would it cause any harm to the valves.
Mike

Herald1360 · 3rd Jan 2014, 2:16 pm

The TX won't cause any harm, but it may be way out on winding ratio. If you know what it came out of, you can check on its primary loading by looking at data for the valve that fed it. A DL92 needs 5K or 8K depending on supply volts, neither of which fotuitously is a particularly unusual value.

Just as an aside, you may find that a fairly large speaker would produce more audio from the limited power available.

Mike Brett · 3rd Jan 2014, 4:34 pm

Thanks for the reply. The valve that fed the small audio transformer was a EL41, I have looked for data on this valve but cannot find what I need to check the transformers suitability.
Mike

ukcol · 3rd Jan 2014, 5:01 pm

Data for the EL41 gives Ra as 7k so your transformer should work quite well with a DL92.

Herald1360 · 3rd Jan 2014, 5:06 pm

Mike,

"Franks electron tube data" and www.r-type.org are both excellent resources if you've not met them.

http://frank.pocnet.net/sheets/155/e/EL41.pdf

is a small sample of the delights.

Mike Brett · 3rd Jan 2014, 5:38 pm

Thanks very much guys for your usual excellent advice.
Cheers Mike

3rd Jan 2014, 1:48 pm	#1
Mike Brett Retired Dormant Member Join Date: Dec 2005 Location: Wisbech, Cambridgeshire, UK. Posts: 452	Battery valve output transformer Hi all I am building a small battery valve amplifier that uses a DAF91 and a DL92. I intended to use a small speaker along with a small output transformer that was salvaged from an old radiogram chassis. I was just wondering if this output transformer would be suitable or not, and would it cause any harm to the valves. Mike

3rd Jan 2014, 2:16 pm	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Battery valve output transformer The TX won't cause any harm, but it may be way out on winding ratio. If you know what it came out of, you can check on its primary loading by looking at data for the valve that fed it. A DL92 needs 5K or 8K depending on supply volts, neither of which fotuitously is a particularly unusual value. Just as an aside, you may find that a fairly large speaker would produce more audio from the limited power available. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

3rd Jan 2014, 4:34 pm	#3
Mike Brett Retired Dormant Member Join Date: Dec 2005 Location: Wisbech, Cambridgeshire, UK. Posts: 452	Re: Battery valve output transformer Thanks for the reply. The valve that fed the small audio transformer was a EL41, I have looked for data on this valve but cannot find what I need to check the transformers suitability. Mike

3rd Jan 2014, 5:01 pm	#4
ukcol Rest in Peace Join Date: May 2003 Location: Harlaxton, Lincolnshire, UK. Posts: 3,944	Re: Battery valve output transformer Data for the EL41 gives Ra as 7k so your transformer should work quite well with a DL92.

3rd Jan 2014, 5:06 pm	#5
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Battery valve output transformer Mike, "Franks electron tube data" and www.r-type.org are both excellent resources if you've not met them. http://frank.pocnet.net/sheets/155/e/EL41.pdf is a small sample of the delights. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

3rd Jan 2014, 5:38 pm	#6
Mike Brett Retired Dormant Member Join Date: Dec 2005 Location: Wisbech, Cambridgeshire, UK. Posts: 452	Re: Battery valve output transformer Thanks very much guys for your usual excellent advice. Cheers Mike