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FERNSEH · 23rd Apr 2017, 2:34 pm

The signal paths have been worked out. The receiver has two RF amplifiers employing EF50 pentodes. Another EF50 functions as the mixer and an EC52 triode as the local amplifier. So it follows that the receiver has only two IF vision amplifier stages. The 4.5Mhz sound IF is taken off from the anode of the mixer and supplied to a tuned circuit and then to the Mazda SP61 pentode amplifier. The sound demodulator and audio amplifier stages are unaltered.
The vision demodulator diode type D43 has been replaced with an EB34 double-diode, the spare section functions as a white spot clipper.
So we now know how this wonderful circuit works it's now time to find out if it works and preserve as much of it as possible.

DFWB.

23rd Apr 2017, 2:34 pm	#20
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: HMV 1804 Television. The signal paths have been worked out. The receiver has two RF amplifiers employing EF50 pentodes. Another EF50 functions as the mixer and an EC52 triode as the local amplifier. So it follows that the receiver has only two IF vision amplifier stages. The 4.5Mhz sound IF is taken off from the anode of the mixer and supplied to a tuned circuit and then to the Mazda SP61 pentode amplifier. The sound demodulator and audio amplifier stages are unaltered. The vision demodulator diode type D43 has been replaced with an EB34 double-diode, the spare section functions as a white spot clipper. So we now know how this wonderful circuit works it's now time to find out if it works and preserve as much of it as possible. DFWB. Attached Thumbnails