Maybe it’s just bad luck, but after a little more than a year my sublime sounding Elrog 300B tubes died inside my TU8600. I confirmed this with the guidance and support of Victor. Through calls and emails and a pro bono shipment of 300B tubes for testing we concluded that the Elrog tubes had failed. I can’t afford nice new tubes right now, but when I can, you can be sure they won’t be Elrog and they will be from Victor.
Recently built the 8600 with all the extras, I have 2 sets of tubes. Cosser is beautiful, Western Electric is sublime. Depending on budget, can't go wrong with either.
i checked all the test points. are the heater voltages included in those? the numbers came back to normal once new 300b tubes were installed.
I do not have the schematics for the TU-8600, but based on my experience with their other amps, they are certainly included. It should be 5V DC near the power tube sockets.
Not until the voltages have been checked. If they are off, the WE tubes will not last long either.
Just following up here… With new tubes, all test points measured within range - including the two test points near the power tubes that target 5V. I agree it is strange that both Elrog failed within hours of each other. At first, I discovered one channel was quiet. I swapped the tubes and then either immediately or very shortly thereafter both tubes were very quiet. At that point I measured the test points, found an issue, and then resolved the issue after installing good tubes.