Behringer BX300T dead amp

[malukaluis]

Dry joints are by far the most irritating faults to repair.
It's the not being absolutely sure of where the fault actually is when going over the board. Once done and the unit is working there's the "did I get it or was it the whole taking the unit apart that fixed it".
But it sounds like you nailed it well done.

[stoneattic]

I'm trouble shoot one of these right now and found this thread.

Mine has been flaky when first turned on a couple of times but other than that was working fine until practice last night. It comes on fine, the lights and VU meter is working but no sound out. That's the same as I noticed before but usually I got sound after a minute of two, kind of like a tube amp warming up.

I swapped cables and speaker cabs, still no sound. I plugged the LINE OUT into the RETURN on another amp and got sound, tried the opposite and got nothing. So it looks like the preamp is fine.

We practice in the garage and most of the gear, except guitars, stays out there, unheated except when I'm out there. It never gets really cold in there but it was chilly (probably in the low 50s (F) and the first time the amp has been in the cold. So I pulled it apart thinking I would begin with a solder reflow based on the history of "slow" starting and figuring if it's a bad solder joint the cold might have worsened it.

When I got it apart I was sad to see all the surface mount on the control board. I figured I need to pull the power amp/heatsink and decided I didn't want to get into it tonight but just for kicks reseated all the internal cable connectors. Of course I plugged it back in and it worked fine. So now I'm not sure if it was a connector or if it decided to start working again for no reason. I'm leaning towards reflowing everything under the heatsink anyway, but was looking for any other thoughts.

Also, I'm not seeing what malukaluis found and posted earlier and think that my problem might be similar. Any chance you can repost?

Thanks!