One channel cuts out as I turn up volume

[AndrewNep]

Hi All,

This is my first post.

Recently I built the Bottlehead  Crack. It sounded great for a while. Resistance and voltages checked out fine. Now when I turn up the volume one of the channels cuts out.

I was thinking of using some flux (which I didn’t originally beside what was in the core of the solder) and reheating all the soldering connections.

Good idea?  Any thoughts?

Thanks!
Andrew Nepo

[Larpy]

Sounds like a bad solder connection.  No need to use flux alone.  Instead inspect all of your solder connections that are in the signal path of the channel that cuts out.  One trick is to turn the chassis over, turn on the amp, and with headphones on and the volume set low, gently tap each solder connection with a chop stick.  When you find the bad connection, you'll hear it make noise as you tap.

Reflow that solder connection using a little bit of fresh solder.

[Paul Joppa]

Don't use flux!

Most fluxes are corrosive (including the one called "Nokorrode"!) and will damage your amp.

Well, OK, there are rosin electronics fluxes available, but be very sure you have one of those before you try it. The flux in the solder core is rosin-based and safe for electronics, and is usually enough without added flux.

[Paul Birkeland]

Plug in some cheap headphones that you don't mind damaging and play music through the amp.  Turn the volume up till it cuts out, then poke around with a wooden chopstick until you find the place where poking brings the music back.

[AndrewNep]

Thanks for the info everyone. I’ll keep working on it over the weekend.

[2wo]

Try exerciseing the pot A dozen times or so with the power off, maybe a dirty contact

[AndrewNep]

I used some old headphones, turned on the amp, played music through it, used a chopstick to test connections, and the thing that made both channels work was if I pushed the bottom of the volume pot toward the chassis plate. I tried pushing the solder connections on the volume pot too but that didn’t work. Those connections all seemed solid. It was only when I pushed the volume pot toward the chassis that worked. Any thoughts on this one?  Thanks!

[Paul Birkeland]

It is somewhat possible to have flux sneak into the pot if a ton of solder is used when soldering the pot lugs.  In this case you'd want to e-mail replaceentparts(at)bottlehead(dot)com about getting a replacement volume pot.