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Ed_Dinning · 28th Mar 2021, 4:38 pm

Hi Folks, a little investigating on HBWoody's board
The transformer is reading 93uH /0.4R the pri and 992mH/ 40R on the sec, all measured on a TF2700 bridge, with sensible Q figures on loss balance.

The anti parallel diodes on the sec showed about a 30% imbalance between forward drops as measured on an AVO resistance range

The Styroflex cap measured at 1.96uF, no leakage

Looking at the circuit the transistors are spec'd as various gain grades of 2N2926's. BC549's are fitted

From the Towers book we have VT1 must have a gain >235 @2mA
VT2 gain >55 @2mA
VT3 gain >90 @2mA

BC549's can go as low as 110 @ 2mA.
The towers given equivalent is BC109, which can go down to 120 @ 2mA; so something to think about there!

Ed

28th Mar 2021, 4:38 pm	#105
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: AVO 163 amp board ~ transformers Hi Folks, a little investigating on HBWoody's board The transformer is reading 93uH /0.4R the pri and 992mH/ 40R on the sec, all measured on a TF2700 bridge, with sensible Q figures on loss balance. The anti parallel diodes on the sec showed about a 30% imbalance between forward drops as measured on an AVO resistance range The Styroflex cap measured at 1.96uF, no leakage Looking at the circuit the transistors are spec'd as various gain grades of 2N2926's. BC549's are fitted From the Towers book we have VT1 must have a gain >235 @2mA VT2 gain >55 @2mA VT3 gain >90 @2mA BC549's can go as low as 110 @ 2mA. The towers given equivalent is BC109, which can go down to 120 @ 2mA; so something to think about there! Ed