Right channel output dropping [resolved]

[larcenasb]

Hello all,

I've been enjoying my Crackatwoa greatly for just about two years now. Everything was working perfectly from the start. However, just lately the volume in the right channel droops very low while listening. I noticed if I turn the volume knob up, the right channel makes a little click and comes back to the same level as the left. But then, over time, the volume droops low again.

Anyone experience this or have an idea what might be causing it? I'll try troubleshooting any suggestions later in the week. Thanks for any help. Cheers

- Lowell

My system: Chord Mojo 1 -> DIY Mogami IC -> Bottlehead Crackatwoa -> AKG K240 Sextett

 

[Doc B]

Pretty much the same as we always recommend - run the amp upside down and poke at various connections with something non-conductive to see if you can create the dropout or create the situation where the level comes back up when it is dropped out. Check all your voltages and report any that are out of spec. Try different tubes.

 

[larcenasb]

Thanks Doc, will try these steps later in the week and will report back. Cheers

 

[larcenasb]

Alright, first troubleshooting was all the easy stuff, one at a time: switched input tube, switched output tube, switched headphones, switched input, switched DAC ...all to no avail.

I then flipped over the top plate to take a look at the circuit and solder joints. Nothing jumped out as a bad/cold joint. When I completed the build two years ago, the joints were shiny and all resistance and voltage checks were good.

So, as Doc suggested, I turned the amp on while the top plate was inverted. And after downing a Monster for extra alertness, I carefully started probing the amp with a plastic chopstick, gently tapping on solder joints. First the RCA jacks, then the input selector, the balance pot, volume pot, tube sockets, terminal strips, output caps -- and there! The channel comes and goes when I tap one of the right output cap solder joints. The joint looked a bit dull upon close inspection. I turned off and unplugged the amp then reflowed the joint, added a little more solder, and kept the heat on the joint for a few more seconds before pulling the iron tip away. Nice and shiny!

All's good again! I've been listening for the past three hours and the output is strong, even, and without any drops.

Thanks for the checkup, Doc!

 

[Paul Birkeland]

Bravo!

 

[Doc B]

Cool! This is why we suggest simply going thru a Crack and reflowing all the joints if you have this kind of issue. Works fairly often and takes maybe 15 minutes.

 

[larcenasb]

Thanks PB! Thanks Doc!

Like I said after building this, so happy with it and am keeping for life.

 

[Thermioniclife]

Love the Spinal Tap "IT GOES TO ELEVEN, THATS ONE MORE RIGHT" Looks great hope you enjoy it. I use a C2A and Mainline depending on what flavor I need that day.

 

[larcenasb]

Thanks, Lee! Yeah, I'm just so happy with the Crackatwoa. And aw man, I've always been curious about a Mainline too. Awesome duo you have to choose from! Cheers and enjoy!

 

[Thermioniclife]

The Mainline is my go to amp, having said that I was on the fence for a while but it proved itself as a very articulate amp but the C2A is no slouch either. I plan on building a stand to hold both instead of lugging one amp off and lugging the other out.  I use them with an ANK 2.1 DAC. I plan on building a rack to hold them both similar to my Monamour stand

 

[larcenasb]

Purpose-built perfection. Sah-weeeeeet!

 

[larcenasb]

Oh noooo! While listening tonight, something strange happened. The channel slowly faded out again ...but not the right channel. This time it was the left channel. What could cause drops in either the right or left channel? Could it be a power supply thing?

This weekend, I'll examine the solder joints again, do the chopstick test, and do voltage/resistance checks. Any insight beforehand, or tips on what to focus on, is much appreciated. I'm actually excited to demystify this and refine my problem-solving skills. Thanks for any help as I work on this.

 

[Karl5150]

Sorry to hear you have another gremlin, I'm sure you'll get it sorted. As mentioned, that is a great looking build. Touches like the black acorns and the vol/bal panel make it look very professional.
Karl

 

[Paul Birkeland]

What could cause drops in either the right or left channel? Could it be a power supply thing?

A bad solder joint (or two).

 

[larcenasb]

Thanks Karl, yes, I’m so happy with this build. And oddly happy with this speed bump as it’ll be a good learning experience.

Alright PB, I’ll examine tonight. However, I’m starting to think perhaps it’s my detachable output cap mod… Remember I used detachable spade connector things to be able to switch output caps easily? Which of course I’ve never done because I love the sound as is! But when I did the chopstick test, perhaps it wasn’t the joint but the connector next to it causing the intermittent output. I’ll take a close look at that as well and perhaps will remove it.

Hope all’s well and hope everyone reading has a great Friday!

 

[larcenasb]

Alright, problem solved!

Even though last time I thought it was a bad solder joint because the chopstick tapping test on the joint caused drops in output....what was actually going on was those taps were vibrating to the nearby removable spade connectors. So now I realized that tapping the spade connectors was the culprit. Since I never used the removable spades to roll output caps anyway, I decided to now hardwire the caps properly.

No more drops when doing the chopstick test! And music is coming through steady and clear.

PB, I remember you said not to use the spades before I started my build saying they wouldn't be reliable lol. Well, after a couple years, you ended up being right as usual. Sorry for not listening! I was so excited to make this amp a tweaker's paradise. But now I realize the amp as is gets me lost in my music and that's more important. Next project will be adding linseed oil to my newer curly maple base. Cheers all.