I have a faulty Philips PM3240 oscilloscope. The problem is that the spot is not showing up anymore. The spot is sometimes illuminating very rapidily for one 10th of a second as a one off and then disapears for 1 hour. I have checked the modulation signal applied to G1 and it seems fine. The CRT is a D14-125 GM/08 but i do not have its characteristics and it is difficult to find out if the voltage between the wehnelt and cathode are correct or not. There is a ZA1004 neon which is acting as a voltage stabilizer between the cathode and wehnelt. This ZA1004 seems to stabilise 230V but i have no idea if this is correct or not as i cannot find any information about this component. The voltage values of the CRT are as follows:
G1: -1500V G2/G4: +33.4 G3: from -950 to -1120 (focus) G5/G6: ground G7: +45V G8: 8KV
I've also checked the filament and it's current is constant even when the spot is not displayed.
Any help would be greatly appreciated !
Cheers,
Thierry.