| There is an 85 ohm resistor from one end of R7 to the chassis so it is probably the reason that you see 120 vac there as well. A check with the ohm meter between each terminal of the switch and the three terminals of the potentiometer should tell you if there is a short. While you are at it, you might check from each terminal of the switch to the case of the potentiometer. Earlier I think you said that you measured 4ma. If this was an AC current reading and if this was with the meter connected between the chassis and the wall outlet ground then we are talking about 30K ohms. If it was a DC current reading then we are talking about 65K. In either case the short is not "hard". The fact that the chassis is negative means that the short is probably to some point that normally sits at +260 VDC. This is consistent with a short between the line and the 5Y3 filament circuit. |
Will Hodges 
TonyC 