[nortonz]

I have 7 XXL tubes, and all but 1 check bad, the one had no filament, so I know it’s bad. But all the others check bad on my Jackson 648s. Some of my other tubes check goo, but not the XXL tubes, but they all check at 30 and 40. Is this normal?

[Radioroslyn]

On my 41-300 both of the xxl's were weak/unusable. Poor performance @ the low end of the bcb.

[W8ZV]

Hi Nortonz!

A Jackson 648 is an emission style tester, so if those tubes don't pass the emission test on the 648, they are probably bad.  However, the best way to know for SURE is to put them in a working radio and compare the performance of the radio.  Both R.L. Drake and Collins radio suggested that method to be SURE that the tube was indeed bad.  I wouldn't pitch the XXL's until I had a working set to plug them in to, so as to make a definite determination.  BTW, if memory serves, an XXL is the same as a 7A4.  But that is the only other sub for an XXL.

[nortonz]

That’s my plan, I have three 37’s on order, when they com in for my 41-295, I will try them to know for sure. BTW your memory serves you well the 7A4 is the only sub for a XXL.