17-09-2020, 02:36 PM
Of course the line output transformers were designed to operate at 15,625Hz whereas in the Philips EHT unit it is 1,000Hz. I believe the method of operation is that the transformer "rings" by the application of the pulse present at the anode of the EL38 and the duration of the oscillation is chosen so that it is sufficiently diminished before the next pulse comes along.
Sometime ago I removed the 25KV overwind from the line transformer of an Ekco CT104. This set is electrically identical to the Pye CT70 dual standard colour TV set. After removing the overwind it was found that the pulse waveform at the anode of the PL509 isn't sufficient with a tripler to produce the required 25KV.
Looking at a GEC 2040 single standard line transformer we find there is an EHT overwind consisting of 100 turns or thereabouts.
A few insulated turns were wound on the Ekco's transformer and it was found that the flyback pulse on 625 lines was about 8 volts per turn.
Geordie McBoyne.
Sometime ago I removed the 25KV overwind from the line transformer of an Ekco CT104. This set is electrically identical to the Pye CT70 dual standard colour TV set. After removing the overwind it was found that the pulse waveform at the anode of the PL509 isn't sufficient with a tripler to produce the required 25KV.
Looking at a GEC 2040 single standard line transformer we find there is an EHT overwind consisting of 100 turns or thereabouts.
A few insulated turns were wound on the Ekco's transformer and it was found that the flyback pulse on 625 lines was about 8 volts per turn.
Geordie McBoyne.
