Silicone conducting?

[RockinRocket]

You sure its not the DC presence pot circuit??

The DC on the pot with have that "crackle" especially noticeable with lot of gain. I notice this with my build and thought of this thread immediately.

Move the presence pot back and forth a bit and see if you can find a good spot where it doesn't crackle.

[mrn1ngstr]

I didn't get a chance to test my theory last night, but I will this evening. Rocket, I feel like its two separate issues. Heres why I think that- the presence pot doesnt crackle when I turn it. Its more like a heavy, distinct rubbing that is independent of the crackle. The crackle corresponds with the movement of the signal up and down on the Y axis of the Oscope. I think whats happening is heater current is entering the LTP via the used flux and into the center lug, then to pins 3,8 and up to the grids from there and screwing with the bias. The flux is not a good conductor, so its not getting consistent current to the grids, which would explain why its not maintaining a consistent bias.

I know most people are going to say flux doesn't conduct electricity, and that is true for the most part... I can tell you that this stuff does, AFTER its been melted. I am usually really good about cleaning up the board after soldering, but I had forgotten to clean a bit that went between a couple high voltage turrets. When I flipped the power, after a couple seconds it began to very brightly arc and burned a pretty small area of the board before I could kill the power. Luckily it didn't do any real damage. I did some googling and it looks like its definitely a thing, and more of a problem for high impedance circuits. I guess Ill find out for sure tonight if Im right about this. I would explain why I couldn't narrow this down to a component or a poor solder joint.

[sluckey]

Maybe you should just remove the flux. Acid brush, mineral spirits, denatured alcohol, hey, there's even an aerosol flux remover.

[mrn1ngstr]

Solved part of my problem. The signal isn't moving up and down now, but the output still looks like crap. Back to the drawing board...

[mrn1ngstr]

Took off the flyback diodes and the crackle stopped. I'm going to replace them and if it starts doing it again, Ill just take them out altogether.

[Noobytube]

Silicone might have been the problem after all? Did u get to the bottom of this yet?

[pompeiisneaks]

Nope silicone can't be the problem, silicone is electrically non conductive.

~Phil

[Noobytube]

Nope silicone can't be the problem, silicone is electrically non conductive.

~Phil

Well, it seems u have it in for me already judging by ur rather condescending reponses to my only two posts! but contrary to ur assertion, I know as a fact that silicone can cause crackling issue in diodes as I had that exact problem in my 50 channel recording console recently, maybe his checking the diode stacks on his output tubes was the problem as he stated removing them made the crackle disappear, aka bad silicone.

[pompeiisneaks]

Nope silicone can't be the problem, silicone is electrically non conductive.

~Phil

Well, it seems u have it in for me already judging by ur rather condescending reponses to my only two posts! but contrary to ur assertion, I know as a fact that silicone can cause crackling issue in diodes as I had that exact problem in my 50 channel recording console recently, maybe his checking the diode stacks on his output tubes was the problem as he stated removing them made the crackle disappear, aka bad silicone.

Nope, I don't have it in for you. I stated a fact, in as neutral form as I could here. In the other post I was defending someone I respect here because I felt your tone was accusing him of lightly making potentially false claims and not backing them up. I may have misunderstood, but I don't recall using terminology more than complimenting norburybrook as someone I trust due to his long standing reputation here. If you took it for anything other than that, it was not only not my intent, but I apologize if you felt so. Silicone can be modified to conduct electricity on purpose, if needed, but by default is in every case I've seen, designed as an extremely good insulator. You'd have to buy special silicone designed to be conductive to get that behavior. That being said, it is possible then, that either you or OP bought electrically conductive silicone, but I think it likely would have had significantly bad behavior as usually silicone is spewed all over multiple components and the chassis and would create a ground for the signal at that point. I may be mistaken, though, and am happy to be corrected and learn something.

~Phil

[Noobytube]

Nope silicone can't be the problem, silicone is electrically non conductive.

~Phil

Well, it seems u have it in for me already judging by ur rather condescending reponses to my only two posts! but contrary to ur assertion, I know as a fact that silicone can cause crackling issue in diodes as I had that exact problem in my 50 channel recording console recently, maybe his checking the diode stacks on his output tubes was the problem as he stated removing them made the crackle disappear, aka bad silicone.

Nope, I don't have it in for you. I stated a fact, in as neutral form as I could here. In the other post I was defending someone I respect here because I felt your tone was accusing him of lightly making potentially false claims and not backing them up. I may have misunderstood, but I don't recall using terminology more than complimenting norburybrook as someone I trust due to his long standing reputation here. If you took it for anything other than that, it was not only not my intent, but I apologize if you felt so. Silicone can be modified to conduct electricity on purpose, if needed, but by default is in every case I've seen, designed as an extremely good insulator. You'd have to buy special silicone designed to be conductive to get that behavior. That being said, it is possible then, that either you or OP bought electrically conductive silicone, but I think it likely would have had significantly bad behavior as usually silicone is spewed all over multiple components and the chassis and would create a ground for the signal at that point. I may be mistaken, though, and am happy to be corrected and learn something.

~Phil

Clearly we got off on the wrong foot, clear written word communication can be a challenge on the webs for sure, I’m a fan of this site, and always intended to sign up and do some builds eventually when time permitted, hopefully my presence can add something here moving forward.

As far as my silicone comment, I had problems with some of my console channel strips that was isolated to what was believed to be a bad batch of diodes, and later found out to be bad silicone(whatever that means ultimately I don’t know), but the rather advanced tech who figured it out instantaneously said that the crackling he heard...”sounds like bad silicone” and he went right to diodes in the preamp circuit, absolutely nailing the issue, we replaced the diodes and problem solved.

[pompeiisneaks]

I guess that could be acid cured silicone. It can eat components.

Sent from my LG-H932 using Tapatalk

[sluckey]

As far as my silicone comment, I had problems with some of my console channel strips that was isolated to what was believed to be a bad batch of diodes, and later found out to be bad silicone(whatever that means ultimately I don’t know), but the rather advanced tech who figured it out instantaneously said that the crackling he heard...”sounds like bad silicone” and he went right to diodes in the preamp circuit, absolutely nailing the issue, we replaced the diodes and problem solved.

I think you are confusing silicon and silicone. Diodes and other semiconductors are made with silicon. Silicone is more commonly found in a liquid or rubbery state and is an excellent insulator.

https://www.livescience.com/37598-silic ... lants.html

[Noobytube]

As far as my silicone comment, I had problems with some of my console channel strips that was isolated to what was believed to be a bad batch of diodes, and later found out to be bad silicone(whatever that means ultimately I don’t know), but the rather advanced tech who figured it out instantaneously said that the crackling he heard...”sounds like bad silicone” and he went right to diodes in the preamp circuit, absolutely nailing the issue, we replaced the diodes and problem solved.

I think you are confusing silicon and silicone. Diodes and other semiconductors are made with silicon. Silicone is more commonly found in a liquid or rubbery state and is an excellent insulator.

https://www.livescience.com/37598-silic ... lants.html

Wow! That’s a mean trick by the phonic gods of vocabulary! I’m gonna have to read up on that, thanx!

[Bombacaototal]

I am wondering which brands and spec of high temp silicon sealant you guys recommend to be placed in between large capacitors to prevent rattling and potentially issues to the soldering

[martin manning]

Get something labeled "Electronic Grade."