Re: Derwent 9" television
Hi Robin,
The circuit of the McMichael model 512 resembles in many respects the Plessey Mark 1 and also your Derwent 9" TV.
The frame timebase circuit of the 512 is very similar to your set. The double triode is a 12AU7 which is also used in some late production Plessey sets. The line timebase is like the Derwent and Plessey Mk1 a self oscillating circuit and employs an EL38.
The circuit diagram of the McMichael 512 can be found on pages 460 and 461 in volume II of the Molloy and Poole Television servicing book.
I'll post up the circuit diagrams tomorrow.
DFWB.
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