AC30CC2 crackling noise

D

dudiluty

New member
Hi there.

I got a AC30CC2. I recently changed all the tubes to JJ and did the Lyle Caldwell mods. But after changing tubes i got some crackling coming out of the amp.. after doing these mods it didn't get worse or better..

I changed all tubes 3 times with new and old ones but that didn't help either.

When i was trying to get the POT pcb out i did have some trouble with getting the switch washers of(they're stuck) so i did those mods from the back of the pcb. Could a switch be damaged?(they all work fine) Or a pot that is dusty?(the top boost volume pot does crackle a little when turning[dust]) But can this also effect the sound when there all untouched ??:confused::?:

The crackling noise gets louder when using all volume controls. Also when no guitar cable is plugged in its worse then with one. When playing it's not noticeable.

I cleaned the whole amp already with proffesional contact cleaner

Any ideas ?

See link for audio sample:
https://www.dropbox.com/s/2krxm621po...noise.m4a?dl=0

thanks
 
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Is there any trick/advice on how to get the glued chrome nut of the little toggle switches ??

I ordered some Molykote DX to lube the pots so i have to access them. To clean and then to lube. Maybe the carbon is gone inside the pots and that's why it's crackling ?:?:
 
Often times if you have what sounds like frying bacon sounds from the amp, it is a bad plate resistor. The easy way to determine which tube is the offender is to unplug one tube at a time starting at the input. If you remove the second tube and the sound goes away, it is most likely a problem with that tubes circuitry. After removing a tube and having no change of symptoms, replace that tube before removing the next one.

If it is actually crackling sounds it could be a bad solder joint, bad socket connection for the tube pins, or even possibly a leaky coupling capacitor. As before, an easy way to find out where a problem resides is to remove the preamp tubes one by one until the problem goes away. When you remove a tube and the problem goes away, it's likely related to the surrounding circuit to that tube. If removing all the preamp tubes doesn't expose the problem, then the noise is probably in the power amp section. As with the preamp section, the same basic symptoms can be attributed to the same components. Pots will become scratchy and crackle if there is dc present on them, which usually means that the coupling capacitor that is part of the tone stack has gone leaky. This is usually the 250-500pf ceramic capacitor that follows a gain stage that connects to the treble pot.

lastly is to do what is called chop sticking. This is where you remove the amp's chassis and place it in such a way that you can turn it on and operate it as well as poke around on the circuit board with, you guessed it, a chopstick ( use wooden chopsticks please ). By tapping, pressing, and otherwise trying to disturb the components, you can often expose where a problem may be. A cracked resistor when pressed on can split enough to be obvious visually and operationally. Tapping on capacitors can show if they are microphonic ( common with ceramic capacitors ). it is just a way to help expose a physical problem like a cracked resistor, cold solder joints, and microphonic parts.

While it sounds like you have some experience with electronics, at least enough to solder, find and exchange components and perhaps even know sort of how an amp works, if you are not sure, you can always pay an amp tech to find the problem for you and you can try and fix it yourself. Most techs charge around $85 for a bench fee, which is more or less the fee to find the problem. Oftentimes though you will find it is just as easy and cheap to pay them to finish the job. At around $25-$50 an hour + parts, most jobs take less than 2 hours, and parts are cheap in the long run.
 
I tried with a chopstick but nothing to hear. I replaced all tubes 3 times nothing helped. I already pulled one tube at a time but that didn't help either.. when i pulled V1 i got no sound at all.

It sounds like a dirty pot. But then constantly without touching anything.
 
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Changed the speaker cables today and tried with a chopstick.. nothing. Also i resoldered every solderjoint on the back of the preamp pcb and cleaned + greased the pots with molykote dx paste(for faders etc).

Nothing helped.

What could cause this crackling:confused::confused: fuses ? I'm getting really confused


I did discovered that when i plug in a cable and my guitar the crackling is gone.. or should this be normal when nothing is inserted in one of the jacks ?
 
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It should not crackle when nothing is plugged in and then quit when something is plugged in. The jack should be shorting out for no input signal when nothing is plugged in.

Have you sprayed some electronics cleaner on a plug and then plug/unplug in the jack a few times? That should clean any dust/corrosion out of the jack. It is also possible that the jack has broken and isn't shorting to ground when it should.

I also had one instance of noise (more like slow motorboating than crackling) caused by a corroded input jack. This noise occurred with or without a guitar plugged in. The amp had been in storage for a few years and the previous owner hadn't noted if it was climate controlled storage or not. When I examined the jack the corrosion was obvious around the threads of the jack. I took the nut off, sprayed some Deoxit on a Home Depot HDX Eraser (like a Mr. Clean Magic Eraser) and twisted that around the jack threads. I repeated this several times until the threads appeared clean. Then I repeated this a few times for the nut threads and nut faces. After that, no noise. I have a new jack. I just haven't replaced it yet, but will if the corrosion and noise return.
 
So when you unplug the V1 tube you have no issues at all? You should not hear any sound that is amplified from the V1 tube if it is removed. So if the problem goes away when you unplug V1, the problem is around V1.

A 12AX7 tube has two triodes in it. This means it has two stages of amplification. This means there are two plate resistors and two coupling caps that surround that tube. The first stage in V1 does the most amplification, meaning if there is noise there at all, it will make it VERY LOUD! The second triode in V1 does some fair amplification as well as it is generally used to make up the gain lost from the tone stack placed after the first stage. I don't have an AC30 schematic in front of me, but In many amps, there is a tone stack right after the first gain stage.

Report back.
 
Ewizard said:
So when you unplug the V1 tube you have no issues at all? You should not hear any sound that is amplified from the V1 tube if it is removed. So if the problem goes away when you unplug V1, the problem is around V1.

A 12AX7 tube has two triodes in it. This means it has two stages of amplification. This means there are two plate resistors and two coupling caps that surround that tube. The first stage in V1 does the most amplification, meaning if there is noise there at all, it will make it VERY LOUD! The second triode in V1 does some fair amplification as well as it is generally used to make up the gain lost from the tone stack placed after the first stage. I don't have an AC30 schematic in front of me, but In many amps, there is a tone stack right after the first gain stage.

Report back.
Click to expand...

When i pulled V1 all the sound did go away.. there was nothing. I already changed the 2 plate resistors and all the tone caps are replaced with mallory 150's. I also tried different tubes in V1 and all the other sockets.. that didnt help so the tubes are fine.
 
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JamesPaul said:
It should not crackle when nothing is plugged in and then quit when something is plugged in. The jack should be shorting out for no input signal when nothing is plugged in.

Have you sprayed some electronics cleaner on a plug and then plug/unplug in the jack a few times? That should clean any dust/corrosion out of the jack. It is also possible that the jack has broken and isn't shorting to ground when it should.

I also had one instance of noise (more like slow motorboating than crackling) caused by a corroded input jack. This noise occurred with or without a guitar plugged in. The amp had been in storage for a few years and the previous owner hadn't noted if it was climate controlled storage or not. When I examined the jack the corrosion was obvious around the threads of the jack. I took the nut off, sprayed some Deoxit on a Home Depot HDX Eraser (like a Mr. Clean Magic Eraser) and twisted that around the jack threads. I repeated this several times until the threads appeared clean. Then I repeated this a few times for the nut threads and nut faces. After that, no noise. I have a new jack. I just haven't replaced it yet, but will if the corrosion and noise return.
Click to expand...

I did clean the inputs and the board with PRF 6-68 cleaner. To be honest i cleaned every bit of the amp. I also resoldered the inputs on the board.. i thought maybe there was a cold solder joint. But didn't help.

Deoxit F5 faderlube.. i have that. But this is a cleaner/lube for faders/pots etc.. don't know if this will do good with other ccomponents ?
 
dudiluty said:
I did clean the inputs and the board with PRF 6-68 cleaner. To be honest i cleaned every bit of the amp. I also resoldered the inputs on the board.. i thought maybe there was a cold solder joint. But didn't help.

Deoxit F5 faderlube.. i have that. But this is a cleaner/lube for faders/pots etc.. don't know if this will do good with other ccomponents ?
Click to expand...

No, I would not use the Deoxit F5 on anything other than faders, pots, etc. Sorry I missed your thorough cleaning note in your OP.

With what you have already done it looks like Ewizard's component around V1. If Chopsticking did not reveal which component, I would turn to the schematic and try to find what voltage(s) is(are) off to identify it. Ewizard may have a better method and his post reads like he has access to the schematic, he just didn't have it when he was posting.
 
JamesPaul said:
No, I would not use the Deoxit F5 on anything other than faders, pots, etc. Sorry I missed your thorough cleaning note in your OP.

With what you have already done it looks like Ewizard's component around V1. If Chopsticking did not reveal which component, I would turn to the schematic and try to find what voltage(s) is(are) off to identify it. Ewizard may have a better method and his post reads like he has access to the schematic, he just didn't have it when he was posting.
Click to expand...

Thanks for the help !
 
Ok i looked at the photos on my phone at work today and i've seen something that makes me nervous. I think the 2 resistors that are marked on the photo in the attachment are 80k instead of 10k ! Look at the colors.... 10k should be brown, black, orange. NOT Grey, black, orange !

I'll open the amp again this afternoon to check to be sure ! Maybe this could be the problem of the crackling and the tremelo........



Update: checked them and they are 10k so there fine. I measured all the resistors and the values are good.
 

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Ewizard said:
So when you unplug the V1 tube you have no issues at all? You should not hear any sound that is amplified from the V1 tube if it is removed. So if the problem goes away when you unplug V1, the problem is around V1.

A 12AX7 tube has two triodes in it. This means it has two stages of amplification. This means there are two plate resistors and two coupling caps that surround that tube. The first stage in V1 does the most amplification, meaning if there is noise there at all, it will make it VERY LOUD! The second triode in V1 does some fair amplification as well as it is generally used to make up the gain lost from the tone stack placed after the first stage. I don't have an AC30 schematic in front of me, but In many amps, there is a tone stack right after the first gain stage.

Report back.
Click to expand...

Sorry was a little confused after looking and searching so much. But when V3(PI) removed everything is quiet(nothing to hear.. should be normal right?). When V1 and V2 are removed the crackling is still there.

I quess it's just a dirty/damaged volume pot of the TB or Normal channel. When only the master is on full i can't hear it now and when i turn the other 2 volumes there is the same crackling noise(when turning). So i think it is making this noise constantly. I'll try some Deoxit F5 this weekend and if that doesn't help i'll have to replace those 2 pots. Still don't now how because those damn chrome nut collars of the toggle switches are glued on :confused:
 
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Ok, we are getting somewhere. So with V3 removed the problem goes away, then it is likely around V3. With V3 being the PI it can be a multitude of things. The coupling caps going to the power tubes could be bad. It may also be any one of the caps from C17 through C23. Any capacitor that is going into the PI or out of the PI basically. What may be suspect is the Cap you changed coming from IC1. That IC has a warning not to use any other type of device. You changed the capacitor coming from it, but that IC is the actual tremolo. The other transistor you have marked is just the switch that turns the Tremolo on and off. Being that your tremolo doesn't work, I would guess that your problem is there.

The downside to most tremolo circuits is that they are always on even when they are off. It is still connected to the PI after all. You can try removing the capacitor C17 to see if that eliminates the noise. Also, be very sure that all your grounds and screws that have ground connections are tight and well terminated to ground. In either case, I do feel your problem lies in the tremolo circuit, which can be a PITA to figure out ( so many components ). The schematic does give you voltages to check against, so that is helpful. You get the fun joy of testing voltages. When you find something that is off, see if you can figure out what component in that area is not working. Often times it is something as simple as a bad connection from a ribbon cable or to ground.
 
Ewizard said:
Ok, we are getting somewhere. So with V3 removed the problem goes away, then it is likely around V3. With V3 being the PI it can be a multitude of things. The coupling caps going to the power tubes could be bad. It may also be any one of the caps from C17 through C23. Any capacitor that is going into the PI or out of the PI basically. What may be suspect is the Cap you changed coming from IC1. That IC has a warning not to use any other type of device. You changed the capacitor coming from it, but that IC is the actual tremolo. The other transistor you have marked is just the switch that turns the Tremolo on and off. Being that your tremolo doesn't work, I would guess that your problem is there.

The downside to most tremolo circuits is that they are always on even when they are off. It is still connected to the PI after all. You can try removing the capacitor C17 to see if that eliminates the noise. Also, be very sure that all your grounds and screws that have ground connections are tight and well terminated to ground. In either case, I do feel your problem lies in the tremolo circuit, which can be a PITA to figure out ( so many components ). The schematic does give you voltages to check against, so that is helpful. You get the fun joy of testing voltages. When you find something that is off, see if you can figure out what component in that area is not working. Often times it is something as simple as a bad connection from a ribbon cable or to ground.
Click to expand...

Thanks for the reply. So C17 could be the bad one in here you mean ? Coming from the IC1B. This one is stock 100nF and i replaced it with a Mallory 150's 0.047uF(mods)

I CAN hear the tremelo a little bit in the background when i put the volume really high. But it's really hard to hear through all the hiss when the volume is that high.
 
Say you dont hear any crackle with the guitar plugged in?

So its only with nothing plugged into the input that he amp crackles or buzzes?

Shame on you with the amp on with nothing plugged in

I wouldn't worry it it doesn't do it with the guitar plugged in.

all my amps buzz and crackle if i turn them on with nothing in the input

I noticed that the other day when setting up my shelving unit of doom
 
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