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Old 23rd January 2016, 10:43 PM   #1
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Smile OPT connections

Hi

I have been given a couple of OPTs out of an old Blaupunkt stereog ram. These have 6 unmarked connections. How best to. Identify what is what with a multimeter?

Thanks avo111
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Old 24th January 2016, 01:36 PM   #2
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Blaupunkt is PP or SE?
If PP - 3 wires are primary....if max resistance is for ex. 400 ohm and 1 wire gives 200 ohm - 2 wires 400 ohm are plate wires and 1 is middle with 2 x 200 ohm for +B.
Remains wires are for speakers 4 and 8 ohm with res about 1 ohm. You must find middle for 4 ohm. 1 is ground, and next are for 4 /res. about 0.5-0.7 ohm/ and third is for 8 ohm with res. about 1 ohm.
If Blaupunkt is SE, 2 wires will give You more 200 ohm.
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Old 24th January 2016, 09:31 PM   #3
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Azazello

Thanks for the reply. I don't know how the transformers were originally wired. What I am measuring is 259 ohm across the primary but the centre tap is 8 ohms to one side and 252 ohms to the other. What I think is secondary is showing about 1 ohm with 0.5 on one side and about 0.9 on the other side.

From this I am guessing this may be an utralinear for a single ended valve. How can I figure out the power rating?

Thanks

AVO111
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Old 25th January 2016, 02:46 PM   #4
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I thing that third wire of primary is about 7% from primary and is for transformer FB for cathode of output tube. Maybe OT is for SE with transf.FB. You can use all primary without central tap.
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Last edited by azazello; 25th January 2016 at 02:50 PM.
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Old 25th January 2016, 09:42 PM   #5
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Sorry, I'm wrong, 7% from primary is separate coil for FB.
UL is 40% from begin of primary. Try to use 259 or 252 ohm for primary.
Has OT air gap between E and I iron parts?
What sq cm is core of OT?
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Last edited by azazello; 25th January 2016 at 09:48 PM.
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