How many valves should be lit up in my dual rec?

[paulburns1984]

Hi all recently bought my first ever mesa, a dual rec, and was just wondering how many valves should i be able to see lighting up in the back of my amp, as i only see 4 actually lit up, but the sounds perfect so I've reason to suspect that a couple have blown! Is this right? Should there be four or six?

 

[domct203]

If you are refering to the two tubes on the right when viewed from the back (5U4GB), sometimes the heater glow is hard to see. Put the amp in a dark room and look again. You should see a faint glow from the heater.

Dom

 

[richt1760]

i

 

[richt1760]

.... but the sounds perfect so I've reason to suspect that a couple have blown!....

I assume you meant NO reason to suspect a couple have blown? All 11 tubes in a DR (5 preamp, 4 output, & 2 rectifier) should glow to some extent, but like domct203 said, it can be harder to tell with the rectifier tubes. I'm not near my DR right now, but IIRC, the preamp tubes are covered, so you really can't see their filiments, anyway. its been my experience that even output tubes glow at different intensities-some are easy to see, some are not. If your amp sounds good, chances of having a bad tube are minimal. Not to mentiion, a blown output or rectifier tube generally causes a fuse to blow. It has with my amps, anyway.