Discussion in 'Amateur Radio Amplifiers' started by KK4YDR, Feb 1, 2016.
How much grid current and HV were you operating them at ?
I put the original tubes back in and the amp worked perfectly! These chinese tubes would not put out more than 650 watts at any setting. BAD BAD BAD tubes!!!
the amp didn't mysteriously change between the eimac and the chinese tubes. The HV was the same. As I recall the chinese tubes were pulling very high grid current at low power levels (Much less than the 1500 watts they are supposed to do) I have read from different sources that the QA of chinese tubes is very unreliable and the customer winds up doing quality control
A customer purchased a so called new 3cx800 tube from Alpha, when they were selling tubes. They are Chinese. The tube is awful and bad from the get go. Not really sure where Alpha was getting those tubes but this one was NG right out of the box. They were selling in the $400 range which is way cheaper than a usual Chinese new tube. Typically a new Chinese 800 sells for around $695 from various brands. A good one however will be fairly close to an Eimac but still there is a little margin of difference. We at Lunar Link tested Chinese tubes at 144,222,and 432 and although they did perform satisfactorily, they were not exactly like Eimac's. Power was up there but at a higher grid current level.
Sounds like a possible biasing difference