What to do if one of the windings should have more voltage

The otherwize excellent TT-47 from tubetown fits my PAS4-clon except for one detail: The 12V winding is rectified and stabilized by a pair of 7812 to create the filament power. 12 Volt is not enough, resulting DC has ripple that causes hum in the riaa stage.

As no other suitable transformer was found and i don't want the cost of a custom transformer another solution is sought.
I will add 10 turns of wire and connect in series with the 12Volt, hoping to get 15 Volts. To be able to do this i will have to make remove the central resin without damaging the transformer.

This is the transformer to modify.

22 mm hole made

First turns

Completet nr of turns needed

This is my wanted 3Volts

But ( there is always a "but" )
The outer diameter is now to large to fit the way it was. :-(

Now everything is in place. Transformer had to change place due to increases outer diameter. Less hum in riaa input ( as expected) 5mV measured at line output. Also installed the quietest fan i could find, a 50mm mounted between powersupply and lineboard compartment. Now the "tube side" measures 45 degrees, earlier it was 55 degrees.

Latest change: 201024

Questions comments suggestions: tubular.well <( -at- )> gmail.com


Feel trapped ?