Crackling tube [resolved]

[klaseck]

Hi!

My first Crack build went perfectly, all voltages good, and the resulting sound absolutely brilliant. After a couple of weeks, a crackling sound started to appear. It seem related to the large 6080 tube; wiggling it changed the crackling, occasionally causing a loud hard pop. Leaning the tube slightly made it disappear, so I disregarded it for the time being.

I then went along to build the Speedball upgrade. Again, it went without problems. However, I missed having the voltage numbers based on my 230 V input here in Sweden. Some readings were rather high, but they matched the relations in the manual. So I went along and started to listen, and the sound was again great, I believe with an even firmer base.

The problem is the crackling, which became more and more frequent, now making it impossible to use. I have cleaned the pins on the tube, and re-soldered all the wires attached to the socket. Wiggling the tube still affects the crackling. Is all of this simply because the tube is damaged, I wonder?

[Tom-s]

A way to test would be the "chop stick method" (Warning, high voltage, be safe).
This is, if all resistances and voltages (or only voltages in your case, as you've installed speedball), check out fine.
Plug in an old pair of headphones and get out a wooden chop stick.
Connect a source and power cord to the amp. Turn the amp on. Turn it upside down.

Now plug in the power cord (in the wall) and let it warm up.

While listening trough the headphones, poke the wooden stick around at various solder joints/connections related to the 8 pin socket.

Other then that, check the whole ground path of your amp for loose connections (trace all black wires).

If all fails, try another tube.

[klaseck]

Thanks, I tried the chopstick method, and all the joints seem fine. The random crackling just keeps going. I had ordered a new tube before the problem got this bad, so I can test if the problem is the 6080 that came with the kit. If that is the case, I assume I can get a new one without any cost from my side? Meanwhile, I guess I have to live without the smooth tube sound. (Not a big issue, considering the strange times we are living in currently, across the globe!)

[Paul Birkeland]

Nearly always this is a solder joint issue.  When you move the tube around, you are moving the solder joints around and restoring whatever connection isn't 100%.  Just touching the tube doesn't do anything internally with the tube.

If you replace the 6080, you will again be moving the solder joints around when you unplug the old tube and plug the new one in, so that may give you a temporary solution to the issue, only to have the noise come back. 

You can post build photos here and we might be able to give you some pointers regarding your solder joints. 

[klaseck]

OK, I attach five images showing my skills...

[Paul Birkeland]

I would go ahead and reheat all of the joints in the amp.  Just heat them up until the solder melts and starts to move around into all the nooks and crannies. 

I would also be interested in seeing a shot of the wiring on your headphone jack.

-PB

[klaseck]

I did reheat all of my "perfect" joints, and behold: the crackling disappeared completely! Sorry for bothering you; I had seen this advice on several other posts. Now the quarantine at home be less boring. Thanks, PB!

[Doc B.]

Doc's theorem - The energy it takes to convince someone to reflow their solder joints is the cube of the energy it takes to actually do it.

[Deke609]

Doc's theorem - The energy it takes to convince someone to reflow their solder joints is the cube of the energy it takes to actually do it.

Hah! And is inversely proportional to that same someone's experience and knowledge. When I first started with diy audio, anything that went wrong just had to be a bad part. A few years later, now understanding a tiny bit and after much soldering and tinkering, I'm certain that problems are the result of me screwing something up -- and I haven't been wrong about the latter yet.  ... And I've encountered a lot of "problems". 

[Doc B.]

For me this goes back 30 years. Whenever I looked at an antique radio that wasn't working the seller would say "it just needs a tube."  Needed a recap, yes. Dusting the tuning condenser, yes. New power cord, usually. Dial cord, yes. Alignment, quite often. But a tube? Hardy ever.

So now after selling kits for 25 years I mostly see the other side - "you must have sent me a bad transformer" "the tube must be bad" "the solder joints LOOK perfect" "the resistor must be bad" "the capacitor must be bad", etc.

To reach enlightenment about this one can work at a bench where kits are coming through on a regular basis. To avoid wasting hours trying to figure out why three unrelated things in the kit are not working the first thing we do is reflow everything. Well, that's the second thing anyway, after checking for miswires. Solves well over half, maybe 3/4 of the problems and saves hours.

We seem to harp on this, but it really is a good thing to try reflowing joints as a first troubleshooting step after you have determined that things are wired correctly. As long as you are reasonably careful and don't gob up the joints worse it doesn't harm anything and often solves problems.

[klaseck]

Thank you guys; your friendly point taken! I will have humble pie for lunch today!