Help troubleshooting please...sharp crackle on note

[Decko]

Hi All,

Finished up another express style build! But unlike my previous builds this one is a bit frustrating trying to troubleshoot.

I have this awful distorted crackle when I strike a note with some force on my guitar. If I hit the note softly...no crackle. get on a string with the pick hard and crackle.

I went through all the solder joints, double checked the wiring, changed the tubes, etc. I am clueless!

Any ideas what may cause this?

Decko

[passfan]

I had something similar from a bad contact in my bright switch. I discovered it one day when I switched to a different position and the noise went away.

[hans-jörg]

Hi,
or any bad solder point. Sounds like.

Hans-Jörg

[Decko]

Thanks...I will go over the joints again..

[jjman]

Bad connection in cathode area and oscillation have caused such for me.

[Reeltarded]

Me too, more than a couple times. I was going to mention that earlier, but I thought it was just me.

[Decko]

Okay, so I noticed oscillation too. This helps to narrow down the issue. Thanks!

Question: I have a Weller soldering iron. I dial it in full tilt at 85. Where do you dial your iron in at?

If solder joints are important, what is the best recommended technique? This may be a dumb question but just curious to see how you all do it.

[passfan]

Did you find it ?

[Decko]

Hi Passfan,

I did locate the issue it was a poor solder joint at the bright switch. I also reflowed all the solder joints on the preamp board and the 12 AX7 tube socket pins. Thanks much for your input!

I still have an issue with a buzzy distortion at the top of the note at low volume. Any thoughts?

Decko

[hans-jörg]

Hi Passfan,

I did locate the issue it was a poor solder joint at the bright switch. I also reflowed all the solder joints on the preamp board and the 12 AX7 tube socket pins. Thanks much for your input!

I still have an issue with a buzzy distortion at the top of the note at low volume. Any thoughts?

Decko

Hi,
in this case you could try a200p to 300p over (parallel) the Anode R of the 2nd (and) or 3rd stage. Try lower and if it gets better higher until its ok.
If it helps nothing - away with it.
Or try an other tube.
Or take a look at your wireing (layout). Crossings only 90°!


Good luck
Hans-Jörg

[Scumback Speakers]

Time to switch cabinets/speakers, or some preamp / power tubes with known good ones. Also look for loose fasteners, or other things in the cab (and in your room).

Good luck.

[Reeltarded]

Yah. Isolate the amp from the speakers to test for vibration is a good idea.

I would check bias, just for giggles..

[Cliff Schecht]

Is your PT properly rated? Undersized PT's have caused crackling issues for me. Excess capacitance on the filter e-caps can exacerbate this problem.

Do you have an oscilloscope? With this you can probe each stage at the plate and see where the crackling is being introduced. This will at least help you narrow down the problem.

Some amp pics and details about components used might help..

I had a Rocket that did something similar to this. It was my 4x 6AQ5 build. I ended up scrapping the build and making a 5F6A instead. I got to the point where I couldn't eliminate the weird note ghosting and figured that the PT I was using was too underrated for the job.

[leadfootdriver]

I had a problem exactly like this. It was a power tube.