That's a very good idea Jeffrey. I have a 3.5kV bench supply which I can try - I wish I was clever, it must be all those fishy oils!
I ran the set with the external EHT generator and the hum has gone!!! Thanks for the nudge, Jeffery. I had thought about EHT smoothing as mentioned in a previous post but I thought it was not easy to check. How wrong I was - it was very easy and it led me to finding the real problem - the EHT smoothing cap was not connected - I had not connected it after installing the rear tag board which carries all the EHT components except the reservoir and smoothing caps. Here is a picture of test card C now:
As you can see, there is still line non-linearity but the line cogging has gone! Strange sets, these electrostatic models. The interaction between EHT and other circuits is much greater but I suppose that that is because, unlike magnetic sets, there is a firm connection between EHT and HT, not just via the CRT electron beam.
The shifted image can be corrected by the adjustable magnets mounted on the inside of the cabinet sides.
This is how the set looks now - very nearly finished!!
PS Excuse the yoghurt pot!
Hi Brian,
Considering the non linearity of the line scan. The picture is slightly compressed on the right side indicating the sawtooth slows up and the end. The ramp forming capacitor C29 is of a very small value I believe, 10pF? The trouble with this circuit even stray capacitances are going to have an influence on the shape of the waveform. Perhaps the capacitor could be reduced by a fraction, it might just sharpen up the waveform.
Cossor got away with only supplying one deflector plate with 500V p-p waveform, the other deflector plate has only DC applied to it. How about a non metalised MS-PEN?
Till Eulenspiegel.
Hmm. I understand what you are saying, Till. The value as given is 20pf but still it's in the realms of strays especially with the older 4V valves. I will make a note of your very good suggestion and try a reduction - say to 15pf but not this week. I have boxed the 54 and am getting to grips with the TSC113, a 15" set - not much of a change from 7"! The EHT used for the 15" CRT is 12kV, mains derived 
so I will be extremely careful with that one!
I think the Visual IF should be about 3-6 mHz and the Aural IF is 2.5 mHz. At least that is how I aligned my set.
I agree Steve. I used 2.5MHz and 3-6MHz as you have suggested. The bandwidth isn't that great, the 2MHz bars are just about discernible but on such a small CRT, that's plenty for a reasonable picture.
