[DMcMahon]

Mk. 5 Update.

Fitted new 3 core mains cable and 3 pin plug.

Checked the mains transformer winding resistances.

Primary :- 110 volt = 18.1 Ohm, 210 volt = 44.8 Ohm & 240 volt = 52.7 Ohm

Secondary:- Heaters = 0.6 Ohm, EZ80 heater = 0.4 Ohm, EZ80 anode to anode = 837 Ohms, Anode 1 to centre tap = 426 Ohms, Anode 2 to centre tap = 411 Ohms

Checked insulation resistance of all windings (Meggered) all OK.

Secondary voltages (DVM) :- Amplifier heater = 6.9VAC, EZ80 heater = 6.92VAC, EZ80 anode to anode = 645 VAC, Anode 1 to centre to 321 VAC, Anode 2 to centre tape = 321 VAC.

Checked that the secondary centre tape connected to correct side of the 47 Ohm current limiting resistor, which it did (the Series 2 connected to the incorrect/earth side).

As far as I could see there is no transformer screen wire connection, the Series 2 had a thin white/pink wire that was believed to be a transformer screen. The Mk. 5 does have a thicker pink wire (same as Series 2) which is the low end (0V) of the primary winding. On the Mk. 5 the mains cable red wire connected to the primary pink wire so technically live connection (as opposed to neutral) but as the mains connector was 2 pin then depending upon how the 2 pin connector would have been fitted then either Live or Neutral would have connected to the primary pink wire.

I would say normally Live/Neutral connection polarity to primary winding would not make any difference, although I have seen a few references to swapping over live and neutral when hum is a problem.

Fitted new dual can 50uF/500V reservoir/filter capacitor and associated 470 Ohm resistor.

Next to check out main components on the amplifier particularly the grid coupling paper capacitors then to connect the amplifier to the power supply and power up.