Good evening,
I thought it was high time I did some more work on this project: With the cold winter nights its very handy to have a TV that produces so much waste heat
I put it on the bench and powered it up to refresh my memory as to where I had got to with it. It soon produced a geometrically very good picture but with awful definition due to the IF stages requiring a full alignment.
It wasn't long before the smell of over cooked mains droppers became overpowering so that decided my plan of attack!
The dropper has to dissipate something in the region of 45W between the heaters and HT sections which is a huge amount of heat. The original was a pretty large thing but was totally knackered and I suspect it was not really up to the job when the set was new.
With some careful juggling of values, I have now used two droppers- one the exact physical size of the original and a second slightly shorter one.
This works very well and gives the correct HT and heater voltages. The HT section had to be higher to compensate for the use of a silicon diode in place of the metal rectifier. So the heat dissipation is now spread over a much greater length of dropper.
There is sufficient space to mount the second dropper below the first one so I think this may well have to become the final solution.
Anyway, it allows me to run the set for longer periods without the solder melting
I can now turn my attention to the low EHT issue. It only reads 10KV with a normal brightness picture displayed rather than 16KV so that will be the focus for tomorrow night.
All the best
Nick