Musicman (Stingray) preamp distortion + pulsing. Any thoughts?

[warwickhunt]

Musicman Stingray 3 band EQ - on first powering up has a very faint distortion but which within seconds builds up and after about a minute sound goes off and there is a pulsing tone.  Has anyone encountered this before? 

 

Fresh battery (twice), leads, cabs and amp swapped and tested so not them.  Bass has been stored in its case (sans battery) for about 4 years.

 

Any insight gratefully sought.  

[DGBass]

I've had pre-Ernie Ball and Ernie Ball Stingrays and the only issues I've ever had were with batteries or the jack sockets. Later 3 EQ Stingrays use a sort of plastic barrel switchcraft jack with a dedicated battery switching contact. If this tarnishes or gets crud in in it, you will get a poor battery supply and the active circuit won't work properly. The pre-Ernieball Stingrays had a much better quality all metal switchcraft jack and the battery didn't go through a dedicated contact like the modern 3 EQ ones. It's well worth getting some good contact cleaner and giving the jack a good skoosh and a wiggle to see if that helps. It may just be a bit of oxidisation from lack of use on the battery contact in the jack.  

[warwickhunt]

dangoose... you nailed it!  

 

I left it with a tech as I am clueless with actually replacing parts of a circuit.  He ran a test; yes there was something going on!  He tested individual components and sections of the preamp, no issues found.  He eventually attached a power to the start of the circuit and scope/test gear at the end... clean as a whistle.  He replaced the battery compartment and the output jack and hey presto sorted.  He's fairly confident that both were contributing and regardless of that he said neither part looked at its best so they were both replaced.  

 

Thanks for the input folks.  Hopefully this is here for future reference/searches.

 

Musicman preamp issues / distorting / jack socket / battery connection