Build Your Own Clone Message Board

My first amp, fired right up, and sounds great. It seems after about 10 minutes or so I get a crackling hum. I am posting the photos of the build, I will take more as needed. I was wondering what would be the best places to look?

https://photos.app.goo.gl/kTFMNC2bzpQ4Zg4q9

https://photos.app.goo.gl/gbCXdFpBZ7MiUhoN9

I will take some closer pics of the sockets later today.

Cool build, man. A 15 watter with an ET65 is gonna sound insane!

Sometimes a crackle like that that occurs after the amp warms up can be a bad tube. 1st step I would do - take off the back panel and run the amp until the crackle starts. Darken the room a bit. Watch the tubes to see if you see any sparks, internal flashes, or just changes in the color (purple flashes in the 6L6). This will tell you if you have a tube that is arcing.



Next for me would be the chopstick test - use a wooden object or some other non-conductive material, and poke at the components while the amp is on to see if poking anything in particular causes the crackle. This helps identify microphonic components and bad solder joints.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

Morgan, thank you for the reply I will check these things. One thing I want to mention is that the lamp seems to faintly dim and brighten at times, is that normal?

Two ideas on the lamp.

1 - bad connection. The lamp runs off the 6.3 volt AC circuit (green wires). If one of the solder joints along that path is bad, you might be getting intermittent continuity. This should not be the cause of the crackle.

2 - the crackle is a short in a tube or other component. When the component shorts, the amp draws a bunch of current and the bulb dims. Note: If this is the case, the short is liable to fry a component unless the fuse catches it and blows first.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

I see like a pulse along the 5Y3 tube when I turn it on.

What is the best way to discharge this if there is an issue so I can resolder something?

The best way to discharge an amp is to understand where the high voltage is and measure that voltage. If you are comfortable with using a DMM, with the amp unplugged, measure DC voltage (1,000 volt range) at the positive end of each large electrolytic capacitor. Most amps do not actually hold much of a charge; the stored electricity tends to conduct through the hot power tubes and out to ground. But not always. Measuring the voltage in the filter caps is what you need to do to know if they have stored electricity.



Do you have any other 5Y3 tubes from another amp to try? That'll tell you if it's the tube or not.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

I don't have a wooden chopstick handy would a plastic one suffice?

Here is a video I made of the issue.

https://youtu.be/SCYirJK1ifU

Yes - as long as it is non conductive

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

Correct me if I’m wrong, but that doesn’t sound that random. It sound like the crackle correlates to how hard you play. I.e. a larger signal makes a larger crackle. Is that correct?

Do you have other known working tubes you can substitute one by one to see if you can identify a potentially bad tube? You can use a 6V6 as a sub for the 6L6.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

I’m also surprised at how little the amp seems to break up at 10 on the dial. I’ve not built this 15 watt version but I’ve built a few 6 watt versions and repair a few originals. They all start to break up quite a bit at around halfway up. That may be a symptom of something; possibly pointing to the 12ax7 portion of the circuit.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

I do have a Fender DRRI I could take a tube out of to check. I believe those are 6V6. I mean random as the crackling seems to come and go.

It does break up half way, but not a great deal.

Sent from my SM-N975U using Tapatalk

Definitely try substituting one of the 6V6 from the DRRI for the 6L6 and a 12AX7 for the 12AX7 in the Champ. Do this one at a time to se if you can isolate the issue to a particular tube.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

Here is a socket wiring view



Sent from my SM-N975U using Tapatalk

One more over the 12ax7



Sent from my SM-N975U using Tapatalk

I tried different tubes one at a time and the issue remains. It seems to be coming from the two instrument inputs especially the black lead that connects to the middle lugs and 1M resistor.

How do you mean? What made you come to that conclusion?

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

I took out the chassis and the brown wire to the instrument jacks was free I resoldered it and the static still remains. So I am lost at this point.

Sent from my SM-N975U using Tapatalk

Okay. Lets reset a little bit.

Good job with the tubes, now we know the 12AX7 and 6L6 are okay.

Did you try the chopstick method yet? Need to use a non conductive stick to move wires around and tap on all the components to see if you can make the noise happen by physically moving something.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

Also, since the input wire connection was bad, there is a chance that another connection is bad. It’s a good idea to go through and resolder all the wire and board connections.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

I did try the chopstick test, no noise was generated by tapping on the tubes or any components or wires.

Sent from my SM-N975U using Tapatalk

I will reflow the connections and see if that helps.

Sent from my SM-N975U using Tapatalk

Just a comment: Based upon what I've observed here over the years, you're more likely to have a solder joint problem on an off-board wire connection than on the turret board itself. So you might want to re-flow those joints first and test the amp, then proceed to the on-board connections if the problem persists. Might save you some time/effort.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Will do thank you I appreciate the help!

Sent from my SM-N975U using Tapatalk

Here is a new video, I reflowed all offboard connections and the issue is still happening randomly.


https://www.youtube.com/watch?v=Ha9Qk6LXUIw