No sound until volume cranked

[lowell]

Got a Peavey MegaBass that has no sound upon turning it on. Once the volume is turned up quite loud BANG sound comes thru. Then I can move the volume down to where I want it and it works. It's not a pot issue...something odd...rail stick? I don't know...my gut tells me it's voltage/rail related. I searched around but am probably not using the right search terms. I emailed Peavey for a schematic as well and waiting for it. They're usually great about that.

Meantime, I checked the first DIP opamp I saw and do get +/-15v on the supply pins. Also of note, the power amp in works fine. It's definitely a preamp issue. So I'm guessing rail stick, or something isn't biased right and the loud signal rebiases it. What I don't get is that once that loud signal hits, it's fine at all volumes. My gut also tells me, maybe a coupling capacitor is leaking.

[Enzo]

Or the preamp cannot reach the power amp.

My instant reaction any time I hear the "I have to crank it hard and then it comes back on" is dirty loop jacks. Make sure the cutout contact on the power amp in is working and clean. Turn the preamp out level control up and patch a cord from full range preamp out to power amp in. Any help?

Also, ther is an insert jack marked send/return next to the inputs, it also has cutouts, check them. The tip is the send so you might also try patching that jack to the power amp is and see if that much works.

Don't we have a sticky thread about the dreaded FX loop jacks?

Even if that is not the problem, you can use those jacks to find if the problem is before or after each jack.

[lowell]

I forgot to mention I jumpered the send/return jacks... cause that's my initial go-to as well. I'll check that jack on the front panel and see, and report back.

[Jazz P Bass]

Don't we have a sticky thread about the dreaded FX loop jacks?.

http://music-electronics-forum.com/a...-20problem.pdf

[lowell]

Enzo does it again. It's the front panel jack. Thanks!

[Enzo]

Almost like we'd seen it a thousand times ...

Just kidding, I'm glad you got it.