Spent the afternoon fault finding, fault still present. Checked all DC rails, all correct and free of ripple. Checked DC voltages around B171, EG -150v, 350v & 500v, all correct. Tested V152 = ok & replaced V161. Also checked R's and C's around B171, all within spec/no faults found.
Took readings as per schematic in post #38, the ones in light grey, these are with the stability control, CCW & CW. - first figures in brackets as per schematic.
Cathodes V173 (+5.4v/-10.5v) +68v/-8.7v.
Pin 7/R172 (+44v/-23v) +60v/+21v.
V161 pin 6, anode (+29.5v/+98v) +33v/+115v.
Lastly V183 cathode (-62.5/_62.5v) -95v/70v.
Voltages on legs of neons B167 (lit) 55v, B171 (not lit) 12v approx, 60v at the top, 68v at the bottom. Presume latter is low and wrong, also something wrong with/around V173 & V183.
Scoped and got waveforms as per schematic on V173 & V183. i then put a 400hz sine into the plugin and got distortion, what the manual calls non-linear traces I think, see pics. Adjusting the X position knob also effects the trace length as well as position, see pics. The last pic is interesting, Y amplitude is maxed out, but the part of the LHS CRT display is smaller than the RHS, IE trapezoid rather rather rectangular.
All this is very confusing as it looks like a combination of TB A fault as well as Y amp fault with possible CRT fault
Any help guidance where to look much appreciated. Andy.
Edit Craig posted at same time. Yes, am a bit out of my depth here, will try Ben, thanks Craig, much appreciated.