Need suggestion for 6.3V-0-6.3V

xecluded · 10:20 PM

Can someone give me some suggestion for a high quality 120V 6.3V-0-6.3V transformer to replace my cheapo radioshack 12.6V CT 1.2A Standard Center Tap Transformer with leads - RadioShack.com (Power transformer, 120VAC step-down to 12VAC, with center-tapped secondary winding (Radio Shack catalog # 273-1365, 273-1352, or 273-1511).

The radioshack cheapo is working fine as filament transformer in my tube amp (for 37 / 76 driver tubes) but running hot to the touch. I need something in compact size that would would well, sounds good and does not cost much (less than $50)

Any pointer is greatly appreciated. Thanks !!!

boywonder · 22nd June 2011, 10:32 PM

Hammond Mfg. - Power Transformer - Economical Single Primary - (166 Series)

Available from Angela Instruments, Digi-key, etc.

What is your required current draw?

xecluded · 22nd June 2011, 10:58 PM

Heater current ................................0.3A
Plate Current ................................. 2.5 mA

leadbelly · 22nd June 2011, 11:13 PM

Each tube is 0.3A, if you have 2 37's and 2 76's for stereo and are wiring them properly for 6.3V, then the load on the transformer is only 50% of it's 1.2A rating. Something is not right.

Tony · 22nd June 2011, 11:18 PM

how hot is hot?
if you can hold that hot traffo for 5 seconds without burning your fingers, then i'd say you have no issue....

MrCurwen · 22nd June 2011, 11:33 PM

Plate current 2.5mA? For two 76's?

I'd say that's quite a bit on the lean side.

HollowState · 22nd June 2011, 11:35 PM

THORDARSON 26F7 FILAMENT TRANSFORMER 12.6 V CT @2 A. | eBay This seller has a good rating.

xecluded · 11:55 PM

The amp uses a pair of 37 tubes driving a single ended 71a amp. I put 76 in there since I maybe swapping in 76 later on to get different sound flavor. I have not done any measurement to find out what is the exact current.

That Thordason on ebay looks like a good candidate. Thanks

nigelwright7557 · 23rd June 2011, 01:10 AM

Use a higher VA transformer to reduce heat.

dgta · 23rd June 2011, 01:52 AM

I've used those RS transformers and there's nothing wrong with them. Measure the steady-state temp and let us know.

If it's running too hot either it's defective or there's something wrong in your circuit. You're not going to find a "compact" transformer (i.e. same size) that runs considerably cooler. They need to dissipate. You may also bolt it real well to the metal chassis to help dissipation.

22nd June 2011, 10:10 PM	#1
xecluded diyAudio Member Join Date: Jul 2008 Location: 10,000 lakes	Need suggestion for 6.3V-0-6.3V Can someone give me some suggestion for a high quality 120V 6.3V-0-6.3V transformer to replace my cheapo radioshack 12.6V CT 1.2A Standard Center Tap Transformer with leads - RadioShack.com (Power transformer, 120VAC step-down to 12VAC, with center-tapped secondary winding (Radio Shack catalog # 273-1365, 273-1352, or 273-1511). The radioshack cheapo is working fine as filament transformer in my tube amp (for 37 / 76 driver tubes) but running hot to the touch. I need something in compact size that would would well, sounds good and does not cost much (less than $50) Any pointer is greatly appreciated. Thanks !!! Last edited by xecluded; 22nd June 2011 at 10:20 PM.

22nd June 2011, 10:32 PM	#2
boywonder diyAudio Member Join Date: Jan 2008 Location: So.Cal.	Hammond 166 series for open style Hammond Mfg. - Power Transformer - Economical Single Primary - (166 Series) Available from Angela Instruments, Digi-key, etc. What is your required current draw?

22nd June 2011, 11:13 PM	#4
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	Each tube is 0.3A, if you have 2 37's and 2 76's for stereo and are wiring them properly for 6.3V, then the load on the transformer is only 50% of it's 1.2A rating. Something is not right. __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

22nd June 2011, 11:18 PM	#5
Tony diyAudio Member Join Date: May 2003 Location: Palatiw, Pasig City	how hot is hot? if you can hold that hot traffo for 5 seconds without burning your fingers, then i'd say you have no issue.... __________________ http://www.electronicslab.ph/forum/i...?topic=32688.0

22nd June 2011, 11:35 PM	#7
HollowState diyAudio Member Join Date: Aug 2006 Location: Taxland, New Jersey	THORDARSON 26F7 FILAMENT TRANSFORMER 12.6 V CT @2 A. \| eBay This seller has a good rating. __________________ "The supercomputer is technologically impossible. It would take all of the water that flows over Niagara Falls to cool the heat generated by the number of vacuum tubes required." ~ Professor of Electrical Engineering, New York University

22nd June 2011, 10:58 PM	#3
xecluded diyAudio Member Join Date: Jul 2008 Location: 10,000 lakes	Heater current ................................0.3A Plate Current ................................. 2.5 mA

22nd June 2011, 11:33 PM	#6
MrCurwen diyAudio Member Join Date: Feb 2010	Plate current 2.5mA? For two 76's? I'd say that's quite a bit on the lean side.

22nd June 2011, 11:52 PM	#8
xecluded diyAudio Member Join Date: Jul 2008 Location: 10,000 lakes	The amp uses a pair of 37 tubes driving a single ended 71a amp. I put 76 in there since I maybe swapping in 76 later on to get different sound flavor. I have not done any measurement to find out what is the exact current. That Thordason on ebay looks like a good candidate. Thanks Last edited by xecluded; 22nd June 2011 at 11:55 PM.

23rd June 2011, 01:10 AM	#9
nigelwright7557 diyAudio Member Join Date: Apr 2008 Location: Carlisle, England	Use a higher VA transformer to reduce heat. __________________ http://www.murtonpikesystems.co.uk PCBCAD40 pcb design software.

23rd June 2011, 01:52 AM	#10
dgta diyAudio Member Join Date: May 2011	I've used those RS transformers and there's nothing wrong with them. Measure the steady-state temp and let us know. If it's running too hot either it's defective or there's something wrong in your circuit. You're not going to find a "compact" transformer (i.e. same size) that runs considerably cooler. They need to dissipate. You may also bolt it real well to the metal chassis to help dissipation.

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