Help ID this OPT

dgta · 24th September 2011, 07:04 AM

Medium size OPTs, silvery grey end bells, numbers 200A1 and 549821 stamped in very small letters in the end bells. Medium size, PP, UL taps, definitely old, cloth insulation on wires.

Would appreciate any info, particularly specs.

dgta · 27th September 2011, 05:34 PM

Bump.

sreten · 27th September 2011, 06:05 PM

Hi,

I guess you could work out the turns ratios by applying 110VAC to the
primary and measuring secondary AC voltages, impedances are the
square of that ratio with 8R load. Very likely though they match EL84's
/6BQ5's or EL34's/6CA7's going on the UL taps, size should indicate which.

rgds, sreten.

Zibi · 27th September 2011, 08:25 PM

? Ham Radio Audio Amp Tube Input Transformer Thordarson
Antique Transformer and Parts Catalogs and Specifications

trobbins · 27th September 2011, 08:44 PM

Probably better to use a lower AC test voltage from the secondary side of a power transformer - as some people may think that they could use the AC mains as a test voltage, which would not be a good suggestion at all.

Ciao, Tim

sreten · 27th September 2011, 09:01 PM

Quote:

Originally Posted by trobbins

Probably better to use a lower AC test voltage from the secondary side of a power transformer - as some people may think that they could use the AC mains as a test voltage, which would not be a good suggestion at all.

Ciao, Tim

Hi, Unless its faultly pray tell why not ? rgds, sreten.

Same issues as testing mains transformers, if they work no issues.

dgta · 27th September 2011, 09:40 PM

Guys, I did measure the impedance, that's not what I'm asking, but thanks anyway.

I want the spec sheet.

OK, after much search I determined 549 is the code for Midwest Coil & Transformer Company. The last 3 are the date, the 21st week of 1958, 1968 or 1978 (the "8" digit).

Now with this info, does anyone have any info, catalogs or links to same for the specs on this particular transformer? Thanks.

24th September 2011, 07:04 AM	#1
dgta diyAudio Member Join Date: May 2011	Help ID this OPT Medium size OPTs, silvery grey end bells, numbers 200A1 and 549821 stamped in very small letters in the end bells. Medium size, PP, UL taps, definitely old, cloth insulation on wires. Would appreciate any info, particularly specs.

27th September 2011, 06:05 PM	#3
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, I guess you could work out the turns ratios by applying 110VAC to the primary and measuring secondary AC voltages, impedances are the square of that ratio with 8R load. Very likely though they match EL84's /6BQ5's or EL34's/6CA7's going on the UL taps, size should indicate which. rgds, sreten. __________________ There is nothing so practical as a really good theory - Ludwig Boltzmann When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

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27th September 2011, 05:34 PM	#2
dgta diyAudio Member Join Date: May 2011	Bump.

27th September 2011, 08:25 PM	#4
Zibi diyAudio Member Join Date: Jan 2006 Location: Bialystok	? Ham Radio Audio Amp Tube Input Transformer Thordarson Antique Transformer and Parts Catalogs and Specifications

27th September 2011, 08:44 PM	#5
trobbins diyAudio Member Join Date: Feb 2009 Location: Melbourne, Oz	Probably better to use a lower AC test voltage from the secondary side of a power transformer - as some people may think that they could use the AC mains as a test voltage, which would not be a good suggestion at all. Ciao, Tim

27th September 2011, 09:40 PM	#7
dgta diyAudio Member Join Date: May 2011	Guys, I did measure the impedance, that's not what I'm asking, but thanks anyway. I want the spec sheet. OK, after much search I determined 549 is the code for Midwest Coil & Transformer Company. The last 3 are the date, the 21st week of 1958, 1968 or 1978 (the "8" digit). Now with this info, does anyone have any info, catalogs or links to same for the specs on this particular transformer? Thanks.