Blue flash when switching standby to on, and hum with reverb

[Dr.Jackle]

Hi,

I thought I'd ask here before taking my amp checked by my dealer.

When I switch standby to on, the power tubes give blue/purple flash. If the 45w setting with the current channel is selected, only the middle pair of tubes flash. With 90 watts, both pairs flash and with 10w engaged, the two leftmost tubes flash. Then they settle down and start glowing a bit purple. I tried to switch the center pair to new Mesa tubes and with 45w setting engaged, the new tubes also gave the flash. I'm yet to try to replace all the power tubes. Does this sound normal?

I have another issue also. When I increase reverb, I get a very strong hum. This is most apparent with clean channel, and with the reverb pot maxed, the hum is so strong that the sound is unusable. The hum increases with the other two channels also, but not as strong. I haven't tried yet to replace the tubes that the reverb uses. Could this be just a tube problem or do I have some major issue with my amp?

 

[phyrexia]

The blue flash is A-OK.

Check your reverb wires, to make sure they are not switched. Then, I would check the preamp tube that drives the reverb.

If this does not fix your hum, it is likely your reverb tank or an internal component of the amp, and you should take it to a dealer.

 

[Dr.Jackle]

Thanks for the answer. I'll try those things tomorrow after rehearsals. I'm pretty green with these things, how do I know if the wires in the reverb tank are wrong?

 

[phyrexia]

Just swap the two cables. They're plugged into the bottom of the chassis. They have RCA ends. If the noise goes away, then you've fixed the problem. If the reverb completely stops working or the problem gets worse, then you have some other issue. If it fixes it then it fixes it