Though I wouldn't go any more than half/twice the current values. Say 330nF for C43. (8M or so for R49).
Steve Anderson wrote: Perhaps there was a later change or an errata issued? I'm using the March 1952 p458 version of the parts list.
Steve Anderson wrote:You do have the advantage that the thing is right in front of you and you can try things and probe around until it's the way you wish. As best as is possible with designs of this vintage that is. But all credit to them, only 21 tubes (active devices) and 4-5 of them were diodes/rectifiers for a complete TV receiver with sound. Many of the tubes were war-surplus at the time implying there were better tubes around but at higher prices probably. They were keen to keep this below 20 quid in 1952 terms.
Panrock wrote:....Would frame flyback suppression be worth a punt? This might just clean up that last straggly line or two at the top of the picture. Steve O
One reason for carrying on is to try 120 lines, on the"PAL" input setting of the old Aurora Multi Standard converter 120 lines is a mechanical derived standard without of course normal electronic syncs. This of course is something I'd need help with.
murphyv310 wrote:Hi Harry.
Many thanks for your nice words.
it has spurred me on to do some more last night and today.
Most of the parts for all the modifications have come from the "junk box" but there were a few things I needed that I don't have.
One of the things I have been short of was a suitable capacitor for EHT smoothing.
I did fit a 0.1uF rated at 6Kv, the value was OTT and 6Kv didn't really have enough headroom so I have ordered some 1nF at 10kV from RS.
These will be ideal. The other thing that the modification needs is some form of line stage regulation. Adjusting the line frequency between standards and setting brightness and contrast changes width and EHT voltage, the reason for this is the use of a large value resistor to get the timebase running at a low voltage. The line scan transformer is intended for a 19 or 23 inch CRT with 110 degree deflection with 16 to 18Kv. I only need 6-7Kv and a scan deflection of 57 degrees.
I have found between 95 to 100 volts, the timebase runs beautifully. So today I added a very basic shunt regulator using a BU2508 line output transistor as a regulator, a zener diode and one additional resistor. The feed to the line output stage is now a solid 98 volts irrespective of brightness or line frequency. The transistor is bolted to the chassis and is running cold.
I still need to sort out a little amount of striations on the left hand of the picture and frame linearity, once the new caps arrive I'll work on the EHT side.
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