Bass amp crackling noise

[KGC]

Hi-

I've got a solid state Peavey TNT 115-BW that I've had since about 1992. When I play my bass through the amp it has Crackling noise through the speaker as if the input cord was bad.

I took the amp out of the cabinet and the speaker to make sure connections were good and fired it up with NO problems. It work great! Put it back in the cabinet and the same problem occured.

This being a bass amp I'm thinking the vibration from the speaker is causing the problem but not sure what to check. Any help would be great!

[Enzo]

When the chassis is out, run wires back to the speaker. Does it crackle through the speaker now?

Either the speaker is intermittent or the amp has a problem. The speaker vibration could be triggering the noise, or the speaker itself could be at fault. Can you connect the amp chassis to a different speaker?

If it is the amp, play something steady through it, ball up your fist and whack the top of the amp hard. Does that make noise? I mean through the speaker. it shouldn't, but if it does, then a connection or solder joint is loose.

Also make sure the nuts on the jacks and controls are tight, those can make crackles if loose. Same with the mounting nuts of the transformer.

If the chassis is out, connect a bench speaker to it and a signal. Whack the ends of the chassis with a rubber mallet or something like one - a dictionary, a frozen chicken, whatever. SOmething to hit the amp with that won't scratch it.

Flex the circuit board by pressing down in the center of it here and there. Any response to that means a bad connection.

[Gtr_tech]

Its more than likely the speaker itself. Those black widow speakers have bolted on magnet assemblies and they can rattle loose and get off center. Also, anoth common problem with those speakers is the black foam junk they put in the polepiece vent as a filter. It degrades over the years and turns into tar. When small chunks break loose and get sucked into the magnet gap it can goo up and eventually lock up the coil in the gap. Take the speaker out and set it on a table face up. tap on the cone....does it buzz or rattle? If so take it apart. *REMOVE* *THE* *FOAM* (or whats left of it) from the p-p vent. Clean out the magnet gap with some masking tape folded so theres sticky on both sides. That will pick up any magnetic particles as well as misc debris. If the foam got in there, you'll have to work it out with some denatured alcohol soaked into card stock. Repeat until the card comes out clean and you can check in the gap with a flashlight to verify its ok. Repeat the tape cleaning step. *CArefully* re install the magnet and put the bolts in just barely finger tight. Tap on the cone to check for rattle, reposition the magnet until the rattle's gone then tighten the magnet bolts.

[KGC]

Also make sure the nuts on the jacks and controls are tight, those can make crackles if loose. Same with the mounting nuts of the transformer.

Thanks ENZO for the advice! One of the nuts on the high input was loose. Tightened it up and no more crackle. Now I won't have to lug my 4X10 cab and heavey amp head to the small gig we're playing this weekend!

Thanks again for all your help!!! You guys rock!!

[phylomatic]

Pictures for proof of what Gtr_tech said it might be.

My dad bought a Peavey Session 500 in the early 90's. It was used when he bought it and it worked well for a long time. It has a great sound, when it works.

I've had a similar problem to what KGC described. It's made the amp unusable for years.

If you don't know about the Session 500, its a pedal steel amp. I'm more of a rock guitarist, so I never had enough incentive to fix it and use it. It's very much usable as a guitarist's amp, but it has a super clean sound, but I digress...

So the incentive came to fix it when I decided to sell it. I took it to a amp repairman and he noticed a few things that were loose, jacks and what not. I don't doubt that what he did had a positive influence on the amp because the keyboardist in the band I'm in used it fine most of the time. Well, I was baffled and I can get a nice price on this amp and someone can use it and put it to great use if it would just work. But I still didn't work on it.

3 or 4 weeks ago a friend of mine brought over his dad's bassman 500 (I know, I know, when will I start using the amps actually made for guitar players). I don't have a cab, and the Peavey, as serviceable as it is, has a nice little extension jack, and low and behold, the ohms will work for what I need. I'm thinking the problem is with the amplifier, not the speaker. The speaker looks just fine.

Guess what happened? The same thing that always happens. I plugged in the Bassman and was completely amazed at how well it sounded. 5 minutes later I'm thinking, "Are my ears adjusting or something?". The speaker started to fade out, just a little, then a little more, then a little more, then it started to distort and finally just started to sound bad altogether. Eureka, the problem is the speaker.

I took the speaker apart tonight and found the exact symptoms Gtr_tech mentioned. It looks like someone spilled a can of dip into my magnet gap. Anyway, I've attached the pictures, take a look yourself. What isn't loose is baked on like bird poo on your car. You can especially see the baked on stuff on the outside diameter where the golden colored metal is (maybe gold, I don't know).

I'm going to clean it up tomorrow night and I'll let you know how it ends up. This has got to be it, but if it isn't I'll update you guys. I'm basically posting this because this is the first post I've seen mention this and if someone else somewhere in America has this problem, then they have something to go on.

God bless the internet.

And just out of curiosity, why does a pedal steel amp have a 15 inch speaker like a bass amp? It seems to me that a pedal steel is even more higher pitched than a standard electrical guitar.

[Enzo]

A steel has a very full range output, I would never characterize it as higher pitched than a regular electric. Guys play a lot above the 12th fret trying to be Eddie Van Halen or someone when it hangs around their neck.

Pedal steel players want it loud and clean and full bodied.

Not a lot of death metal pedal steelers out there.

[Gtr_tech]

I took the speaker apart tonight and found the exact symptoms Gtr_tech mentioned. It looks like someone spilled a can of dip into my magnet gap. Anyway, I've attached the pictures, take a look yourself. What isn't loose is baked on like bird poo on your car. You can especially see the baked on stuff on the outside diameter where the golden colored metal is (maybe gold, I don't know).

You got off easy....I've seen them *much* worse than that.

[phylomatic]

Update

Cleaned the stuff off last night and put the speaker back in the enclosure (didn't do the amp). I tested it with the old bassman head and played for an hour. Played it loud, put distortion through it, tried to cover all the frequencies and had absolutely no issues. Sounds great.

Thanks Gtr_tech, your tips on cleaning the speaker helped a lot. I used the card stock and some patience and got it off. I wouldn't have thought to have used that, I would have used a razor knife and probably messed it up, so kudos. Oh yeah, I also used some Q-tips which seemed to do ok, but they made me much more nervous than the card stock. That part of the speaker is real thin and fragile it seems.

[Gtr_tech]

Glad to be of service.....you owe me a beer
The knife idea is bad mojo for cleaning off both the coil and magnet gap. You don't want to screw up the coil former or the wire, or create any magnetic particles that can get attracted into the gap. Q tips are fine for cleaning the goop off the coil. The card stock idea came from watching speaker reconers prep a basket for reconing.

[cloudeatcloud]

I got a smoking deal on a Peavey 118D bass cab with a 4-ohm 1801 Black Window speaker. I'm guessing it is an 83 or 84. I was planning on replacing the 18 with a brand new speaker because of it's age so I figured I have nothing to lose if I take it apart and find out it's beyond repair. The speaker worked but it had this strange behavior where at low volumes the speaker sounded like a weak mid-range with no bass at all. Once I turn the amp volume up to 4 - HELLO bass! The blast of bass is almost enough to scare you. Bring the volume back down and again the bass frequencies quickly disappear. I took off the magnet and immediately saw the same problem that phylomatic had except mine was a little worse. There is this thick black tar-like sealant smeared around about 1/4 of the inside of the voice coil can. It's also smeared inside the voice coil slot causing the coil to stick at low volumes and starts moving once the amp puts some high current into it. I was relieved to see the voice coil windings look perfect - no dents, scrapes, or burns, measures a solid 3.4 ohms. Obviously a large piece(s) of this dried up & aged black sealant broke off and worked its way into the coil slot.

It was a fairly easy fix but took a bit of time and patience to get all of the black goop off the voice coil can without damaging it. I figured since the voice coil can AND the cone are both aluminum, brake parts cleaner would work great. I probably would not attempt to use brake cleaner if the cone was made out of paper. Brake cleaner might damage a paper cone but it does wonders for cleaning aluminum. I also use brake cleaner to clean the aluminum decoration sides that are a Peavey speaker grill trademark of the '70s, '80s, and '90s. Most people hate those things though. I tried using Q-tips at first but I was afraid I was pushing a little too hard with the Q tip so I used some pieces of an old towel and saturated them with brake cleaner. The voice coil slot was bit harder to clean up. I used the card stock trick to loosen up the tar stuck in the slot, then ended up using some expired gift cards (like credit cards) that I cut into strips to get inside the slot and scrape it clean. It worked great. Also took a razor blade and carefully cut off all the excess dried up sealer in the center of the magnet so I won't have the same problem again, ran a fold of duct tape around the coil slot gap, and gave it a good vacuum before installing the magnet to the basket.

Works like a champ now. I have the cab paired up with a Fender BXR 200 watt head (4 ohm) and it sounds great. Very happy with the fix.

9 years later - Thanks to the comments and suggestions on this blog. I was able to save this vintage Black Window, breath some new life into it, and save some $$$. thanks a million. peace.

[Enzo]

There is a vent hole in the center of the magnet. They put a plug of foam rubber in that vent as a filter. The foam works loose and found its way into the voice coil area. That foam rubber turned into the black goo you found. I have no issue with brake fluid, but I usually have success using alcohol.