Ampeg issues

[xBrBaileyx]

I have an ampeg svt 4 pro that i bought about a year ago used. Until the other day i've never had any problems with it other than the mono brige distroting which is not a problem seeing as in run it stereo anyways. But the other day at practice we were running through a song and I lost most of my volume. The amp had almost no volume and was feeding back and any string i hit gave me these very brittle scraping sounds. Reading p on it i found ppl having this problem and it was their tubes. My tubes were very old so i replaced them. That gave me some volume back but the amp is very muddy, lacking ton. Has and is cutting out and just dosnt have the power that the svt 4 sure. It was a great head before this and i'd hate to have to buy a new head. Anyone have an idea of what that problem may be?
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[fu22ba55]

PM sent with some possible ideas. I've heard a few different things regarding the 4pro.

 

[lyes4string]

check for dirty pots my 5 pro did the same thing was just dirt in almost all of the pots mainly your volume and gain. when you play the vibrations from the bass will actually move the pot just enough to make it crack and sound almost like youre blowing a speaker.

 

[Jerrold Tiers]

Lots of possible issues,

tubes, well maybe.

Appears from the small information we get that it might be either a bad solder joint or a problem with a loop jack having bad contact on a "through" connection, at least as far as the simpler possible problems are..

Try just plugging into every jack several times as a start.... if nothing in the way of tubes or plugging fixes it, you are stuck with taking it in.

Not meaning to jump on you, as you probably have told us everything you can, but it is almost impossible to give a good diagnosis from a description such as this. There just isn't enough information, and you probably have no way to give us more.

The only added piece of easy-to-obtain information would be whether plugging into the power amp gives same result. That's preferably done with an active bass, but even a P-bass will usually give enough output to identify bad problems.

A tech would check lots of things, output on scope at different places inside, voltages, tapping various parts, etc, which you can't be expected to do. Your problem could be anything from a bad connection to a tube problem to a failed component on a PWB...... All problems a tech can identify and fix.