05-10-2021, 08:28 PM
Hi.
I decided to go through this again but using 27v. They follow typical rod pentode characteristics with more output on the G2 with the anode grounded. Between 18v and 27v the output from the anode rose considerably. No doubt with higher HT the anode will perform much better. Triode connecting the valve even up to 27v reduces gain. Using my Fluke multimeter on Diode check give 1.2v between each control grid and f- strapping them gives 0.8v very low indeed for a valve! This also in my mind confirms the valve is dual control grid construction.
I've been using one of those plastic breadboarding experiment panels for tests, easier to work with rather than a birds nest.
I did this in the living room this evening so only a meter to hand. I used two piezo high impedance phones to make a simple AF amp to get some idea of whether it would work. There was reasonable gain between 18 & 27v and even results at 9v on the G2. The valve does feel slightly warm at 0.9v filament volts and the filament is just visibly heating, looks the same as the 1j42a running 1.1v but at a much higher current on the 1ZH26A.
To be fair I really don't see any great advantages using this valve and it may have a shorter lifespan than others, the greedy filament is also another downside.
I decided to go through this again but using 27v. They follow typical rod pentode characteristics with more output on the G2 with the anode grounded. Between 18v and 27v the output from the anode rose considerably. No doubt with higher HT the anode will perform much better. Triode connecting the valve even up to 27v reduces gain. Using my Fluke multimeter on Diode check give 1.2v between each control grid and f- strapping them gives 0.8v very low indeed for a valve! This also in my mind confirms the valve is dual control grid construction.
I've been using one of those plastic breadboarding experiment panels for tests, easier to work with rather than a birds nest.
I did this in the living room this evening so only a meter to hand. I used two piezo high impedance phones to make a simple AF amp to get some idea of whether it would work. There was reasonable gain between 18 & 27v and even results at 9v on the G2. The valve does feel slightly warm at 0.9v filament volts and the filament is just visibly heating, looks the same as the 1j42a running 1.1v but at a much higher current on the 1ZH26A.
To be fair I really don't see any great advantages using this valve and it may have a shorter lifespan than others, the greedy filament is also another downside.
