Mesa .50 Caliber + questions

[andrew]

Hi, I am new here and have a few questions about my newly purchased .50 cal + head. This is my first tube amp.

1. After I turn the power on should I turn the standby off?
2. Can I swap the 6L6 power tubes for EL34's?
3. Can a bias pot be installed?
4. My reverb doesnt work and I would like it to work. The connecting wires are oddly set up kinda hard to explain(I can provide pics).
5. Not all the preamp tubes glow when I am playing. Is this normal?
6. The speakers make a little "squeal"(also hard to explain) noise when I turn the power off and the volume on my guitar is still on

Thanks in advance for any help

 

[LHanson]

Hi there. Sorry it took so long, I just saw your post. I, also, own a .50 cal + **** fine amplifier.

As to your questions:

1. The standby is always off, unless you are playing. The power switch turns on the heaters in the tubes, but the standby lets the signal go to the tubes. The proper way to turn on the amp is to make sure the standby is off (the same position as the power switch off), turn on the power switch, walk away for about 5 minutes or longer, plug in the guitar and all the effects, turn on the standby. The tubes don't like to have signal on them before they are warmed up, and not warming them up can reduce tube life. Turning off is the reverse; standby switch off, wait a few seconds, turn off the power. This also answers question 6. That noise is the sound of the tubes trying to work properly without the right amount of heat. Not pretty, is it?

2.Not directly, but a good amp tech can work wonders.
3.Same as 2. A good tech could probably put a couple of bias pots and a switch to change from 6L6 to EL34.

4. dunno. Maybe tied to question 5.?

5. All the tubes should glow from the heater filaments. Some tubes glow with a halo-or-fog-with-colors kind of thing. Which preamp tube? The quick and dirty answer is to go to the music store of your choice, and buy a 12ax7 an a 12at7, as well as a matched pair of 6L6gc's. You need them as spares. Just pull and replace the non-glowing preamp tube with a new one. Note results.

 

[andrew]

Thank you for the help, much appreciated.
I am going to order a set of JJ's from eurotubes and i'll see if the verb is a tube issue(bob said it may be also).

 

[LHanson]

Also, use the search feature to find more info here. Search .50 cal + and .22 cal + since they used pretty much the same preamp. There have been discussions about tube substitutions, etc. that are worth reading.