As a follow up to my recent Post I've now had a chance to re-check all my voltage readings across this set.
The valve data in the Service Instructions make it clear that all measurements shown therein were taken with an input of 230V A.C. 50 cycles, the Receiver set to medium wave range with no signal and with an AVO 7 with chassis negative. All my measurements have been taken with my Toolzone DMM so some adjustments are required.
All values shown in brackets are from the Service Instructions.
Firstly, the heaters:-
V1 UCH42 13.3V (14.0V)
V2 UF41 11.1V (12.6V)
V3 UBC41 12.8V (14.0V)
V4 UL41 43.0V (45.0V)
V5 UY41 30.0V (31.0V)
Total 110.2V (116.6V)
Secondly, the valve pins:-
V1 UCH42
Pin 2 84.6V (98.0V)
Pin 3 45.3V (47.0V)
Pin 5 45.6V (47.0V)
Pin 7 0.74V (??)
V2 UF41
Pin 2 60.8V (74.0V)
Pin 5 50.1V (57.0V)
Pin 3, 4 & 7 1.04V (0.8V)
V3 UBC41
Pin 2 63.5V (74.0V)
Pin 7 1.05V (1.3V)
V4 UL41
Pin 2 192.7V (190.0V)
Pin 5 84.0V (98.0V)
Pin 3 & 7 4.38V (5.0V)
V5 UY41
Pin 2 208V A.C. (220V A.C.)
Pin 7 204V (205V)
So in general the HT is a bit low across the set but nothing looks particularly out of the ordinary or raises cause for concern??
Also checked the control grid of V2 (UF41) and measured 0.08V (?) while the control grid of V4 (UL41) measured 0.0V.
What I did find was that on some occasions when the set was switched on from cold that the volume was a lot quieter than usual and didn't mute when the volume control was turned to zero. I understand that this may be symptomatic of an ailing UBC41? I accidentally shorted the control grid (Pin 5) of the UBC41 to chassis and found that this cleared the problem?
Any and all feedback welcomed.