~ 2 Odd and badly damaged QUAD IIs inspire my last mod ~

Pictured is a chassis from my 1993 'Black pair' of QUAD IIs taken in April 2020 after being stripped of my triode driver modification and some new design output transformers from Majestic Transformers in Poole UK that I had been testing

Despite the amount of rework they have had in past years the black Hammerite paint finish on the bases still looked good but the black painted transformers and chokes had either failed or had been used for other projects in the past

Majestic had sent me a damaged mains transformer that was dropped by a delivery agent and I managed to remove the damaged can and some potting compound and re–pot it [with very little compound] in an original can that I had from one of the 1993 'black pair'

I purchased a matching core and made another new black mains transformer using an original can I had to hand ~ The Hammerite made now is not the same as the old stuff but I needed to rub down both cans anyway and outside in the heat of March 2020 I got a similar finish to the 27 year old chassis

These are the new output transformer [OPT] cores with my traditional style Majestic core [top left]

The primary and cathode windings are the same as the traditional Majestic QUAD II OPT but the secondary windings use thinner wire and more turns such that each section matches to a 12Ω load

Each section also crosses the bobbin exactly twice and the wire exits the bobbin each side giving each section a centre tap and the 6 sections paralleled similar to the Sowter OPTs I devised in the 1980s

Although I had new bases and turret lugs for the OPTs I decided to sleeve the wires and run them directly to the output terminals and KT66 valve bases

The output valves were to have separate bias resistors so 2 turret lugs were fitted to the base to support the bias resistors and bypass capacitors and provided connection to the cathode windings

The new chokes wound with slightly thicker wire were fitted turned 180˚ to support the other ends of the bias resistors and those wonderful Hybrid Aluminium [polymer] capacitors

The PFTE wiring is now minimum and direct as are the output connections to their terminals ~ the yellow wire is the OPT centre tap which will be connected to input PCB ground and can be used externally to connect the screen of a loudspeaker cable if you have one

Note the rectifier valve base has the unused pins removed ~ This used to be done when the rectifier voltage would be very high but here it makes the valve easier to fit and remove as well as providing sufficient isolation

  Under construction