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trobbins · 21st Jun 2021, 2:58 am

Thanks. So the extra resistor 'loop' is in series with the innermost wound section of the feedback winding (P-Q). It's plausible that the additional resistance or leakage inductance (or both) provided by that 'loop' is balancing some high frequency characteristic.

It does seem a bit strange that the stated resistance of the resistor 'loop' is 0.36 ohm and the stated resistance of P-Q is the same as Q-S at about 0.55-0.61 ohm, and that each secondary winding section that comprises P-Q and Q-S are each comprised of 51 turns. Given the photo of the resistor 'loop' showing only a few turns on a small SRBP strip, I'd expect it to be a lot less than 0.36 ohm given that the wound sections total up to be 0.55-0.61 ohm. Maybe 0.36 ohm relates to the total L2 winding section that contributes to P-Q, and not just the resistor 'loop' itself. As such, it seems that the resistor 'loop' is more about its leakage inductance contribution than its resistance contribution.

21st Jun 2021, 2:58 am	#32
trobbins Heptode Join Date: Oct 2009 Location: Melbourne Australia Posts: 901	Re: Quad II Transformer woes! Thanks. So the extra resistor 'loop' is in series with the innermost wound section of the feedback winding (P-Q). It's plausible that the additional resistance or leakage inductance (or both) provided by that 'loop' is balancing some high frequency characteristic. It does seem a bit strange that the stated resistance of the resistor 'loop' is 0.36 ohm and the stated resistance of P-Q is the same as Q-S at about 0.55-0.61 ohm, and that each secondary winding section that comprises P-Q and Q-S are each comprised of 51 turns. Given the photo of the resistor 'loop' showing only a few turns on a small SRBP strip, I'd expect it to be a lot less than 0.36 ohm given that the wound sections total up to be 0.55-0.61 ohm. Maybe 0.36 ohm relates to the total L2 winding section that contributes to P-Q, and not just the resistor 'loop' itself. As such, it seems that the resistor 'loop' is more about its leakage inductance contribution than its resistance contribution.