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Chris55000 · 5th Sep 2019, 4:37 am

Hi!

Has anyone been able to compile a definitive table of the gate switch functions yet?

I've tried doing it from the Mullard Service Manuals for the E7600/3 and E7600/4 but don't seem to have much luck!

Obviously the first few rows that connect the valveholder tags to the circuit are fairly obvious, it's the ones that select the H.T. and G.B. voltages from the voltage stabiliser circuits by changing over resistors (or combinations of resistors) that seem to be a stumbling block, since there are (theoretically!) up to 255 different function combinations!

The contacts towards the bottom that select heater voltage from the heater voltage transformer are, of course only operated in such a way to connect two distinct taps to the valve–holder supply points at any one time, so a table for the transformer tap gate switch configuration can be drawn up from knowing what the heater supplies from the transformer are, and this data isn't in the manuals! (Or have I missed noticing it somewhere?!)

Incidentally, did Mullard provide selectable anode resistors for Magic–Eye Valves, or was the Magic Eye Triode Anode voltage selected by the normal method for any valve, by selecting the appropriate resistors in the H.T. stabiliser?

(I haven't yet had a chance to study the circuit diagrams in great detail, but me thinks if there are four contacts spare, then these could be used for m.e. triode anode resistors, e.g., 100k (EM87), 470k (EM80/EM81/EM84/EM85), 1M (end viewed, single shadow octals) and 2 × 1M for the EM34.)

Chris Williams

5th Sep 2019, 4:37 am	#123
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,868	Re: Mullard Valve Tester Card Project Hi! Has anyone been able to compile a definitive table of the gate switch functions yet? I've tried doing it from the Mullard Service Manuals for the E7600/3 and E7600/4 but don't seem to have much luck! Obviously the first few rows that connect the valveholder tags to the circuit are fairly obvious, it's the ones that select the H.T. and G.B. voltages from the voltage stabiliser circuits by changing over resistors (or combinations of resistors) that seem to be a stumbling block, since there are (theoretically!) up to 255 different function combinations! The contacts towards the bottom that select heater voltage from the heater voltage transformer are, of course only operated in such a way to connect two distinct taps to the valve–holder supply points at any one time, so a table for the transformer tap gate switch configuration can be drawn up from knowing what the heater supplies from the transformer are, and this data isn't in the manuals! (Or have I missed noticing it somewhere?!) Incidentally, did Mullard provide selectable anode resistors for Magic–Eye Valves, or was the Magic Eye Triode Anode voltage selected by the normal method for any valve, by selecting the appropriate resistors in the H.T. stabiliser? (I haven't yet had a chance to study the circuit diagrams in great detail, but me thinks if there are four contacts spare, then these could be used for m.e. triode anode resistors, e.g., 100k (EM87), 470k (EM80/EM81/EM84/EM85), 1M (end viewed, single shadow octals) and 2 × 1M for the EM34.) Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! Last edited by Chris55000; 5th Sep 2019 at 4:52 am.