Winter project.

[Murphyv310]

   
Hi.
The last few days have been a no no for me. I have done something to my back and I can hardly get about.
Around midday I decided to take two 400mg Ibuprofen which I really shouldn't do as they react with other meds I take. Within a couple of hours I felt a lot better. So I had a couple of hours on and off in the shed. I've been using the Philips projection line scan transformer again, that and the added PY81 and a blocking oscillator circuit from a 1953 Ultra has given me the best results so far.
I did try using a 555 timer as a sawtooth oscillator with some success which no doubt I'll go back to later but the Ultra circuit has by far the best sawtooth with very little overshoot.
I can get full width on 240 & 180 lines. There was some issues with flashover but as can be seen the addition of two pulse caps has tamed the circuit and results are excellent. Take mind the scan transformer is designed for 10,125Hz and its a plus this works and so well on the lower frequency.  
I've quickly sketched out the line stage. The G2 feed to the CRT and the width control is omitted but the Bush width control still works but is rather fierce in its control, from a postage stamp to full width!


The EHT doubler diodes need to be suitably rated as does the their caps, I am now using a PY88 just to balance up the heater chain as the PZ30, PL38, are no longer and subsitiuted with PL36 (30P4 or 19) PY33 & PY88. A cap dropper will be fitted eventually once more mods are done.
Next will be more work on the frame timebase.
Some more pictures on the next report.