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theredhouseinn · 21st Oct 2020, 1:52 pm

Back on the problem of the special adaptor for the Z759 pentode.
I see from the base connections for the Z759 that the heater pins are 5 & 6, different from the usual 4 & 5 pins for a B9G base.
Putting in card 1106, with a IO plug in the IO socket, I get 6.8vac between pins 2 & 7, heater supply.
Pins 1,4, and 8 show a short to chassis, cathode and grid 3?
pin 3 has -1.95v to chassis, obviously the control grid supply.
Pins 5 & 6 both have 252vdc to chassis, anode and grid 2, but which is which?
The resistance between pins 5 & 6 is 220 ohms.
Any idea's chaps before I make up an adaptor.
I stand a 50 50 chance of getting the anode connection correct.
If it dosn't work I can always swap pins 5 & 6 round.
John.

21st Oct 2020, 1:52 pm	#20
theredhouseinn Hexode Join Date: Jan 2013 Location: Kelvedon, Essex, UK. Posts: 273	Re: Mullard HSVT Back on the problem of the special adaptor for the Z759 pentode. I see from the base connections for the Z759 that the heater pins are 5 & 6, different from the usual 4 & 5 pins for a B9G base. Putting in card 1106, with a IO plug in the IO socket, I get 6.8vac between pins 2 & 7, heater supply. Pins 1,4, and 8 show a short to chassis, cathode and grid 3? pin 3 has -1.95v to chassis, obviously the control grid supply. Pins 5 & 6 both have 252vdc to chassis, anode and grid 2, but which is which? The resistance between pins 5 & 6 is 220 ohms. Any idea's chaps before I make up an adaptor. I stand a 50 50 chance of getting the anode connection correct. If it dosn't work I can always swap pins 5 & 6 round. John.