How do I measure OPT impedance?

roundel325 · 30th April 2004, 03:59 PM

I've got a pair of telefunken OPTs. They are marked:

P=10,000Gktc
s1=4
s2=8

My first problem is that I don't know what leads are 4 and 8 ohm. Secondly, the input side has 3 leads, so I'm wondering if "Gktc" somehow means "center tapped" in german, which would be great, because I'd rather use the 5k primary if there is one....

Any help is appreciated. Thanks.

-Jared

speaker · 30th April 2004, 07:28 PM

Some Telefunkens used a common, 4-5 ohm, and a negative feedback tap on the secondary side. Output from the feedback usually went to the front-end. You do not have 4 & 8 ohms hook-ups.

Your unknown tap on the primary side maybe a humbucker tap. Some Telefunkens ran all B+ through the output transformers and then stripped it off, out-of-phase and sent to main supply filtering for the rest of the radio. It was out-of-phase to reduce hum because the radio was SE.

Do you know what model they came out of?

speaker

30th April 2004, 03:59 PM	#1
roundel325 diyAudio Member Join Date: Mar 2004 Location: Ohio	How do I measure OPT impedance? I've got a pair of telefunken OPTs. They are marked: P=10,000Gktc s1=4 s2=8 My first problem is that I don't know what leads are 4 and 8 ohm. Secondly, the input side has 3 leads, so I'm wondering if "Gktc" somehow means "center tapped" in german, which would be great, because I'd rather use the 5k primary if there is one.... Any help is appreciated. Thanks. -Jared

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30th April 2004, 07:28 PM	#2
speaker diyAudio Member Join Date: Mar 2004 Location: USA	Some Telefunkens used a common, 4-5 ohm, and a negative feedback tap on the secondary side. Output from the feedback usually went to the front-end. You do not have 4 & 8 ohms hook-ups. Your unknown tap on the primary side maybe a humbucker tap. Some Telefunkens ran all B+ through the output transformers and then stripped it off, out-of-phase and sent to main supply filtering for the rest of the radio. It was out-of-phase to reduce hum because the radio was SE. Do you know what model they came out of? speaker