Ampeg SVT 350H Crackling on low tones

[Liningerm]

Hello, first time posting here but have always read good advice on these forums. I have an Ampeg SVT 350H bass head I've been working on. Whenever I play low notes on my bass, usually between E and G on the E string, the amp crackles and pops and the limiter lights up. It seems to get better when I turn down the bass on the eq, and gets worse if I use anything on the front end that increases gain even slightly, such as my wireless setup. I recorded myself practicing and it happened, so I uploaded it to youtube so maybe someone can kind of hear what I'm talking about and have an answer.

my playing isn't the best, but it'll give you some idea.

 

[Stumbo]

If you have an active bass, you may want to try a new battery.

 

[Raw N Low]

Sounds like the amp might need to be cleaned. Maybe try some dioxit in the input and send/return loops to see if that helps. Also, you mentioned that you're using a wireless setup. I would try using a plain jane cable from bass to input and see if this cures what ails you.

The wireless system might be kicking the bucket, or you might need to change the channel on the receiver.

 

[Liningerm]

So I opened it up, found a transistor was loose and wobbling. I bought a new one and replaced it and it's gotten better, but when I lightly tap the amp it crackles and cuts out.

 

[JimmyM]

So I opened it up, found a transistor was loose and wobbling. I bought a new one and replaced it and it's gotten better, but when I lightly tap the amp it crackles and cuts out.

Cold solder, maybe? Maybe one in that area that isn't the transistor?

 

[BassmanPaul]

So I opened it up, found a transistor was loose and wobbling. I bought a new one and replaced it and it's gotten better, but when I lightly tap the amp it crackles and cuts out.

How much do you know about servicing electronics? A tech would be a wise investment.

One thing to try is to link the Send and Return of the Effects Loop with a short signal cable. Same for Pre-amp Out and Power Amp In if it has them.

 

[BogeyBass]

Bad solder joint somewhere on the board.

maybe input jack

just guesses really.
very long board that flexes so at likely flex points.
youll see component leads going throw the solder pads and the solder cracks in a circle around the lead.
input jack is the first best guess, hundreds of others. jack gets pushed on all its life. eventually flex crack the leads

poke n push the board with chopstick or something plastic to find the likely area
and listen for crakle