20-11-2023, 11:58 PM
(This post was last modified: 21-11-2023, 12:02 AM by Geordie McBoyne.)
The RF EHT generator in the 1952 HMV model 1820. Note the HT voltage doubler with two U107 diodes for the anode of the KT36 oscillator valve. The HT voltage is 380V.
From the service manual. A description of the RF oscillator: "The EHT unit consists of V24 (KT36) working as a "class C" RF oscillator with L46, C78 and TC8 as the "tank circuit" and L43 as the "feedback" winding. Grid current bias is established by R98 and C78.
Coupled to L46 is a low capacitance winding L47 producing 7.5KV feeding a conventional voltage doubler rectifier arrangement."
The metal cone CRT employed in this set had a short in-service life span.
Geordie McBoyne.
From the service manual. A description of the RF oscillator: "The EHT unit consists of V24 (KT36) working as a "class C" RF oscillator with L46, C78 and TC8 as the "tank circuit" and L43 as the "feedback" winding. Grid current bias is established by R98 and C78.
Coupled to L46 is a low capacitance winding L47 producing 7.5KV feeding a conventional voltage doubler rectifier arrangement."
The metal cone CRT employed in this set had a short in-service life span.
Geordie McBoyne.
