Quote:
Originally Posted by retailer
Having just returned from a few weeks away doing nothing I'm eager to get to the Dynaco SCA 35 kit amp I recently purchased - the mains transformer is the US 110V 60Hz version and I plan to rewind for 240V operation, I found a small stack of matching laminations so I have enough to add to increase the core area to cope with the decrease in mains frequency, the chassis and transformer mounting holes are elongated and I worked out I can go from a 50mm to a 65mm lamination stack and still mount the transformer in the original holes. I'd like to make some small changes to the winding layout the original power supply has 2 non centre tapped filament windings, one for each channel, and a split secondary, approx 315V - 0 - 315V feeding a pair of silicon diodes, giving a HT of 370V I'd like to change this to a single winding with a bridge rectifier, this will make the winding of the transformer a bit easier for me and will allow me squeeze in a shield winding between the mains and secondary windings, in addition I'll try to wind the filament windings as bifilar windings which will give a true centre tap which may allow me to eliminate the 'hum bucking' 1k pots - does any one see any issues with my proposed idea.
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You are only using the original lams, end bells and mounting brackets?
A few design additions:
Add in a thermal fuse as used in modern transformers
Add a few extra taps to the primary in case of mains voltage fluctuations, eg +/- 2.5% or whatever mains voltage drifts you measure.
Add a couple of secondary taps to get the the HT just right.
What are you using to make the bobbin? Are you replicating the vintage build style eg paper between each layer?
Doug.