5150 Combo Problem

[ewhelan]

Hi Jerry,

I just found your site and I am thrilled to see some tech info on the 5150 Combos. I have been looking forever for this it seems. I have been having a few problems with my 5150 Combo and I'm hoping you guys can offer some assistance.

When I tap on the plastic air grate on the top of the amp, I can hear a pinging through the speakers. Is this normal? Also, I find that the amp is really thin sounding and I would like to change that.

I'm proficient with a soldering iron (to the point that I have actually soldered pins back on a broken P4 processor) and I know a little about electronics.

Thanks for any help or suggestions you can offer.

[Jerry P]

Sounds like you have a microphonic tube. Try tapping on the 12AX7 tubes and see if you can figure out which one it is.
Jerry

[ewhelan]

It was a microphonic tube. I'm amazed at what kind of negative effect one bad tube can have on an amp.

Thanks Jerry!

Now I might sell it.....and buy a boogie

[Jerry P]

ewhelan said:

Now I might sell it.....and buy a boogie

Oh man that hurt!
Jerry

[ewhelan]

Sorry Jerry,

I'm at my wits end trying to get a good sound out of this amp.

I can't seem to get anything I like out of it. I find it has WAY to much midrange....and the bass not tight at all....and when you turn it down it gets too thin.

I hate the gain in the lead channel......really buzzy

I just think I would be happier with a different amp.

[Jerry P]

ewhelan said:

Sorry Jerry,

I'm at my wits end trying to get a good sound out of this amp.

I can't seem to get anything I like out of it. I find it has WAY to much midrange....and the bass not tight at all....and when you turn it down it gets too thin.

I hate the gain in the lead channel......really buzzy

I just think I would be happier with a different amp.

I was just messing with you, the Mesa's sound good. I personally hate the 5150 combo. It sounds nothing like the 5150 head IMO.
Jerry

[ewhelan]

I went through the "perhaps a mod will fix it" phase and I searched high and low for some documented 5150 Combo mods....but 99% of the mods out there are for the head which is a different circuit.

Then I realized that, even though a mod might change it, it probably wouldn't change it enuff for me to like it.

It's sad.