[Phil G4SPZ]

I think I'm correct in saying that the current transformer only operates on the AC current ranges plus the 10 volt AC range. Looking at the circuit diagram, the P.F. terminals are indeed directly across the CT secondary (with a total of 40 kilohms resistance in series) but the CT secondary is shunted by the instrument rectifier and the movement. The rectifier will present a non-linear load, and hence measuring the actual voltage at the P.F. terminals may not be particularly informative.

I'd add to Dave Philpott's suggestions that low readings on AC ranges can be due to the single diode S.A.1 across the moving coil being leaky - I've encountered this on at least one occasion. This protection diode is only there to cause the movement to move and trip the cut-out in the event of AC inadvertently being applied to the meter whilst set to DC, so you can cut it out completely and it won't affect the accuracy of the instrument.