Re: The "Sussex" Homebrew Valve Tester.
I've been asked by Martin "G8UWM-MildMartin" to add some notes to the 'Bill of Material', it's now at version 12.
The reason for the updating the ‘Bill of Material’ was the original design by the late Mike Rowe, there was update (see the last paragraph). Lets call the original Version One, there are two further design versions a Four and a Nine, these updates are thanks to Martin “Dekatron”.
The original consisted of three boards, Main, Daughter and Low Voltage Heater.
Version Four only one PCB board was used and two Power MOSFETs are used to supply voltage to the Anode and Screen grid switches. Also linear voltage regulators are used to obtain the low heater voltages.
Version Nine, a daughter board (LR8 board) is mounted on main PCB which removes the series Zener Diodes, ie ZD1...ZD7 arrangement and uses a high-voltage, low-output current adjustable linear regulator (U1). to control two Power MOSFETs (TR2 & TR4) for the Anode and Screen grid voltages.
The schematic diagram has TR2 & 4 as IRF830, but the BOM (Post #974) captured by “Herald1360” on a post #104 before it disappeared has them listed as BUZ80, theses are not available at Farnell but STP3NK80Z are. Which are rated at 800 volts at 2.5A, this explains why they run cool, requiring no heat sink.
Mike G4WYZ
29/10/2018
NB
The picture is competed Sussex.
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