6L6, 6L6G, 6L6GA, and 6L6GB are all glass bottle early versions that will not work (for very long!) in a Mc amp as they have a Max plate watts of 19, Max plate volts of 360 and Max screen volts of 270 @ 2.5 amps.
6L6GB is Max plate watts of 30, Max plate Volts of 500, Max screen volts 450 @ 5 amps.
Ron-C
Isn't the 6L6 the same as the 1614?
"Red plating is not an issue using 6L6GC tubes as long as the amp is in proper operational condition" Really? My 240 was rebuilt by Audio Classics several years ago, so that the 6L6GC tube with red plating is no issue? The tube itself (rca black plate) tests. very strong, but it's red plating in less than a couple of minutes.Here is what McIntosh said:
"McIntosh amps will correctly perform with 6L6GC tubes. The earlier 6L6 tubes do not have the voltage rating to work in these amps. Red platting is not an issue using 6L6GC tubes as long as the amp is in proper operational condition."
Perhaps whoever started the red plate rumor was using non-GC tubes.
Thank you!!!Be sure the second 12AX7 that is associated with those 6L6GCs has clean pin contacts and that the tube socket pin receivers for the 12AX7 tube are also clean. Any corrosion on that tube's pins or in the socket can cause loss of grid bias on the 6L6GC associated with it and result in red plating.
But it looks like 12au7 was responsible for the red-plating. Actually I've been wondering why I got this red plating in the 6L6GC tube when it tests so strong. Thanks for your timely reminder. Without it, I would have never double checked that tube on the far right. I feel the sound with the right tube is more lively & dynamic!A 12AU7 in that position will do it too. Glad you got it solved!