I changed the output tubes in an older ARC VT-60 and had the same thing happen. I am curious as well. I had read online that whenever you replace the tubes in an amplifier you should automatically check and adjust your bias (which makes sense). This particular guy had posted the process for a VT-100 ... it was not a quick and simple process. It required the use of a multimeter and in fact, he advised using two meters and it also required interpreting a schematic. It's been a while since I have been down and dirty with the guts of a tube amplifier (25 years?) but the old electronic technician in me read further. The output tubes were fairly simple to adjust but the input tubes required a fair bit of finess. I decided to call in the big dogs and have my local guy do it but I am going to watch and photo the process so the next time I can do it.
In the mean time I have continued to run the amp just to see what happens ... call it morbid curiosity. The amp seems to have mellowed out and I dont see any more blue glow. I figure at worst I will replace the tubes with a new set which I have already acquired. The sound is fine ... in fact it's very nice with the new tubes in. If had heard anything that scared me I would have taken it in. I bought the little VT-60 just to learn a little before I dive into the more expensive units.
My logic tells me - if the bias was to high on the input tubes they would over drive and I would know it. If they were to high on the output tubes (where I noticed the blue light) it may be more difficult to spot so I have kept the volume down until I can get it in to be checked.
Any advise out there would be appreciated ... books, websites, and technical sources? remember I am a newbie and not an engineer.
In the mean time I have continued to run the amp just to see what happens ... call it morbid curiosity. The amp seems to have mellowed out and I dont see any more blue glow. I figure at worst I will replace the tubes with a new set which I have already acquired. The sound is fine ... in fact it's very nice with the new tubes in. If had heard anything that scared me I would have taken it in. I bought the little VT-60 just to learn a little before I dive into the more expensive units.
My logic tells me - if the bias was to high on the input tubes they would over drive and I would know it. If they were to high on the output tubes (where I noticed the blue light) it may be more difficult to spot so I have kept the volume down until I can get it in to be checked.
Any advise out there would be appreciated ... books, websites, and technical sources? remember I am a newbie and not an engineer.