Tube Options:   Photonis Echo: These tubes are Gen 2 by US definition due to the lack of GaAs (gallium arsenide - a semi conductor) though technically they are a hybrid technology as they utilize a multi-alkali photocathode. Whereas Gen 2 of the "old days" used a bi-alkali. Photonis tubes featu... View Post

“Blem” and “Dark Spots.” What do they mean?Dark Spots:Dark spots are inherent to the manufacturing process. Could be a particle sandwiched in the intensifier, fiber optic, or various other circumstance. All tubes are allowed dark spots. This is why there is a prescribed dark spot allowance. Dark ... View Post