WARNING

    There are two distinct models of RA17L, the British Military version, which uses CV
    numbered valves and the North American model, which uses U.S. commercial valves.
    The valve sets for these two models are different. Several valves, whilst similar in
    function, have a different pin-out. Inserting the valve from the other set will almost
    certainly result in destruction of the valve and may cause damage to other components.
    In particular, many substitution guides give 6AS6 or its variants as equivalents for the
    S6F33 (special 6F33 - V4). In fact the connections to G2 and G3 are reversed and the
    connections to the base must be changed to do this substitution.
 
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