[MFJ-Ameritron] About The 3-500

[Duane Fischer, W8DBF]

Hello All, 	
	
Can somebody explain to me the advantages and disadvantages of the various types
of 3-500 tube? Such as: the 3-500, 3-500zg and so forth.   	
	
I have heard mostly negative things about the Chinese tube, why? I have heard it
works alright in single tube applications using about 1200 volts, but the tubes
arc and fail when used as a pair and operating at 3600 volts. Is this correct? 	
	
The graphite version is supposed to have better disipation and longer life.
Correct or not? 	
	
Who makes the most dependable 3-500zg?	
	
Thanks. 	
	
Duane Fischer, w8DBF