• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

OPT connections

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#2
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.
 
#3
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
 
#4
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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#5
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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