Is the red glow normal for 845 tubes?

Sorry Tiofelon, I misread your post and noticed that your tubes glow red after 25 minute of being powered up and a couple of minutes when powered off. This is still not normal for a standard 845. What is the Sino 845 dissipation rating? Perhaps it is a lower dissipation 845 (around 65w-70w) and your amp is designed for a standard 845 dissipation tube. Most graphite plate 845 tubes conform to the RCA standard with some carbon plate and some metal plate variants having a lower dissipation rating. Are the tubes biased correctly??

Thank you Brf and Dopogue for your input! According to the manufacturer the dissipation rating for the Sino 845 is 70W. The amp is a self-bias so there is no need for adjustment. The tubes in question are Sino 845 (not B, C or W). I got the amp second hand with this type of tubes and I do not know if these tubes are the originals. I wrote to Bel canto about the dissipation requirement for the SETi 40 tubes but so far I have not received an answer. I should clarify that the red glow is present in 95% de the graphite plate, and after shutdown it last about 2 min. If I continue using the amp this way would I damage something? So far I have used the amp about 150 hr and I like it very much, I just noticed the red glow last night!! because I lisen music during the day. Thanks again for your help!

The Bel Canto amp is designed to run the 845 tubes at the NOS RCA standard dissipation of 100w, therefore, you are running the Sino (70w) low dissipation tubes 40% over their optimal operating rating, which accounts for the red hot spots on the plate. Red hot spots on the plate are a sign of an over driven 845 tube. You will not harm the amp, but the tube life will be significantly shortened. You have 3 options 1) run the current tubes until they expire 2) change the tubes to a higher dissipation 845 3) have the amp modified. I would opt for #2.

Thanks again Brf. I just run into an article in VTV (vacuum tube valley) where it says "graphite es heat-resistant (in fact, it can operate with a dull red glow for a long time without failing)" in power tubes like the 811 o 845. However a new set of 845 tubes is coming my way.

Red glow in morning, audiophile take warning! Sorry, sometimes I just can't help myself.