[Radioroslyn]

I'll mention in passing 26's kind of oddball tubes. The filament voltage is very low (for an ac operated tube) and the current is high. From what I've read it was to replace the 01A (5.0v fil). There was 71A and 112A 5.0 tubes. These were throwback from the battery days. I think it's the only 1.5v @ 1.05A. I'll make the recommendation if you test them I would measure the filament voltage @ the pins when it's in the tester. You may find that it's low. You could adjust the line set pot up to get the proper voltage but not sure if that would affect the hv and bias voltage.