peavey 5150 still sounds bad

[torpedoted]

Im srry im retarded when it comes to this stuff your saying plug an instrument cable into the preamp out on the 5150 to the guitar input on the marshall? Then plug my guitar into the 5150?

[Jazz P Bass]

You got it!

[melvin]

I just though I should add that the 5150 still has to have speakers attached. There won't be any sound from it, but unless you take the power tubes out, the amp needs a load.

[exclamationmark]

A common problem in 5150's (and basically all derivatives made by Peavey) is that the effects loop gets clogged up with random shit and starts sucking tone in sometimes not so obvious ways because it thinks something is connected. Get some contact cleaner and spray some in the jacks (not too much!) and on the end of a guitar cable and start ramming in and out (insert appropriate analogy) of the effects loop jacks. Also sometimes the effects loops jacks will rust and cause all sorts of problems (which might be the case if it's been sitting for 3 years).

Also it may just be that you simply don't like the amplifier. 5150's tend to be quite dark sounding, probably to tame the stupid amounts of gain. Saying this though, it still should get plenty bright when you crank the presence/treble.

[torpedoted]

You know what I mentioned somthing about the presence how it doesnt kick in till u turn it up to 8 or more. I think their is somthing wrong with my power amp cause the presence and resonance control is in the power amp right? but what do you guys think as far as what could go wrong in the power amp to make it sound the way it does?

[Jazz P Bass]

The Presence & the Resonance controls are both in the feedback path, coming from the output transformer.
There are roughly 40 parts involved in the ouput stage.
What you want to know is which one(s) is (are) making the tone bad.
Without stepping on any toes, I think you need to take the amp to a competent tech.

[Trace]

Really quick;

1.) Running the Presence that high is pretty common. The solution is to change the pot and also install a post with a different taper to it.

2.) Regarding the amp being dark; Yes this is pretty common on the 5150's.

3.) Screen Grid resistors - I would recommend checking these as it's very common to have a faulty/full shorted screen grid. They are 100ohms and should really be 470ohm 5 watters. I would recommend upgrading these to 470ohms one way or the other as it's a good preventative measure.

4.) If it's an original 5150 with the "EVH" block letter - when you pull the rear power tube board to replace the screen grid resistors you may want to check the diodes as often times when you blow a power tube it arcs leaving a carbon track on the pcb.

5.) Upgrading the transformers does help but first you should convert the amp to adjustable bias so you can get it biased where it should be. I would recommend the Ruby 6L6GCMSTR's or the SED 6L6's, though the SED's have gone in a great deal in the past few months. I would also go with Chinese preamp tubes but make sure all the tubes are properly burned in first as it does make a marked improvement.

6.) If the above mentioned does not give you what you are looking for then it makes good sense to Upgrade the transformers to Mercurys. They sound great and are built well.


Hope it helps & all the best;
Trace