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Author Topic: Crackling noise from Peavey Valveking 100  (Read 4587 times)

Bakeacake08

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Crackling noise from Peavey Valveking 100
« on: December 07, 2015, 12:57:22 AM »
My buddy asked me to repair his Peavey Valveking VK 100 amp head for him; he left the speaker cord in and the amp fell over, so now the jack needs to be replaced. He also asked me to try to figure out another issue he has been having since he's owned it (so before the damage), which is a sort of scratchy, crackling noise it makes. The noise is a little pop sorta like when you plug in a guitar cable while it's on. It's not very loud though, easily overpowered while playing. It does not come at regular intervals and can be anywhere from once every couple seconds to a couple every second. None of the pots seem to have an effect on it. It is considerably louder on the gain channel and faint (though still noticeable) on the clean channel. I tried hitting it a little to see if it was an obvious mechanical thing, but nothing changed. I played through the amp for about twenty minutes or so and afterward didn't notice it before I turned off the amp. I didn't have time to tell if it was totally gone or just taking a break. I haven't opened it up yet because I haven't had time to put together my light bulb limiter. Your thoughts?


Oh, and I have also had trouble finding a proper schematic for this amp. All my searches seem to point me towards either the Valveking combos or the new line of heads. Anyone know how to find one for this specific model?



Enzo

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Re: Crackling noise from Peavey Valveking 100
« Reply #1 on: December 07, 2015, 04:27:56 AM »
Call Peavey customer service for any of their schematics.  The 100 head is the same circuit as the 212 combo.  I use the 212 drawing when servicing the head.

Bakeacake08

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Re: Crackling noise from Peavey Valveking 100
« Reply #2 on: February 15, 2016, 01:10:59 AM »
Finally had time to dig in and here is what I found. About half the solder joints look like they punched through when the amp fell over, so the obvious first step is to clean those up.


When this board was still connected to the circuit (with now power), I plugged in a cord to easily check the connections, and for some reason it was reading as having no resistance between the tip and the sleeve. It was the same for both output jacks, and again when I checked it on the actual solder connections. It was an open circuit after I pulled this little board off. What might cause this to happen? The outputs seemed to work fine when I last tested it, so I found that rather odd.



Enzo

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Re: Crackling noise from Peavey Valveking 100
« Reply #3 on: February 15, 2016, 04:06:28 AM »
That is because you are measuring the resistance of the output transformer secondary winding.  It is a low number of turns of heavy gauge wire, so it has VERY low DC resistance.  Perfectly normal.

Bakeacake08

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Re: Crackling noise from Peavey Valveking 100
« Reply #4 on: February 15, 2016, 01:39:05 PM »
Oh right. That makes sense.

Bakeacake08

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Re: Crackling noise from Peavey Valveking 100
« Reply #5 on: May 05, 2016, 01:32:09 PM »
I cleaned up the solder joints and put everything back together. It's still making that little popping noise. It sounds similar to the pops you might hear from a little bit of dust when listening to vinyl records. I tried tapping components/tubes to see if I could figure out the source, but no luck. Is this something I can fix or just the nature of large tube amps?

Enzo

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Re: Crackling noise from Peavey Valveking 100
« Reply #6 on: May 05, 2016, 05:04:05 PM »
It is not the nature of any amp, large or small, tube or solid state.

I am sure it can be fixed, whether you yourself can do it is a matter of your skill and tenacity.

You said the controls make no difference, but that it was louder on the gain channel.  That is sorta contradictory, if you get me.  We need to isolate the problem.  First, does the amp do this across town at someone else's house?  Noisy electrical environments are everywhere.  I have unwanted noise sources here in my shop even.  I see things like furnace/AC motors coming on and off making noise, my dad's fish tank heater thermostat made noise.  One day I went nuts trying to find a hum in an amp that happened for maybe 45 seconds every minute or so.  Turned out it was the traffic signal at the end of the block had a noisy triac and every time it was red one direction I got noise on the electric service.   So we need to eliminate that.

Then in the amp.  Does turning ALL controls to zero still leave the noise?  Plug the guitar into the FX return and zero out its volume control.  Still noise or no?

Connect the FX send to some other amap and listen, do you hear the noise over there?

Bakeacake08

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Re: Crackling noise from Peavey Valveking 100
« Reply #7 on: May 08, 2016, 06:10:01 PM »
Success? The amp was noisy on the other side of town where my buddy lives, so I knew it was something inside the amp. Turning all the knobs to zero made no change. I plugged into the FX send and nothing appeared on the second amp. When I plugged into the FX return, the noise went away. Then when I unplugged from the FX return the noise stayed away. So I'm thinking there was dust or something in the contacts that got knocked loose with the plug inserted. Is there anything further I should look for before returning the amp, or does that sound like a reasonable explanation?

Enzo

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Re: Crackling noise from Peavey Valveking 100
« Reply #8 on: May 08, 2016, 06:18:03 PM »
Well, it sure sounds like the cutout contact in the return jack was dirty.  Just plugging into it might have cleared the problem.  That happens fairly often.  And if it returns, plug a spare cord from send to return to bypass those contacts and get through the rest of the gig noise free.

However, one test I always do:  the cutout contacts should measure close to zero ohms, anything under half an ohm is good.  I measure them with a meter.  If they measure one or two ohms, the amp will usually work as if nothing was wrong, or even 20 ohms, hey I am generous.  But the fact it isn't half an ohm or less means the contacts are compromised, and need cleaning.  And the problem WILL return if not cleaned.

So get out the ohm meter for a quick check.

Bakeacake08

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Re: Crackling noise from Peavey Valveking 100
« Reply #9 on: May 08, 2016, 07:15:01 PM »
Sounds good! Where do I measure? I'm not familiar with how these jacks work mechanically.

Enzo

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Re: Crackling noise from Peavey Valveking 100
« Reply #10 on: May 08, 2016, 07:44:40 PM »
Look at the jack, its operation ought to be intuitive.  Plug something into it and watch.  You can see the tip lift up the crosswise contact when it is all the way in.  You can see that contact would otherwise sit on the little lower one.  Underneath the two pins at that end are either side of that contact, so measure resistance between those two pins.

phatt

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Re: Crackling noise from Peavey Valveking 100
« Reply #11 on: May 09, 2016, 09:46:46 AM »
Just like to add to Enzo's comments. A pic might help. (with a little rant from me) :grr.

The switching setup on almost every Amp that has a series FX loop or preamp-out/ poweramp-in is all the same, done by a switch which is built into the socket.

That switch is by far the most common failure mode of guitar amps. :duh
The reason that they give so much trouble is because of cost cutting.
This picture should be obvious.

I have 3 Cliff switching sockets in this picture, the Red is the oldest, (must be over 40 years old by now) Notice how it has proper silvered brass contact buttons on both sides.

These switches hardly ever fail because they are made the RIGHT Way,, (well there are even better units but Gold is rather expensive 8|)
The Green socket I purchased much later, the cheap black unit is only a few years old.

The Black unit is now the standard you will find in most amplifiers and it does not take long before they give trouble. :'(
A couple of tin plates is not a switch in my books but they get away with it. :trouble

Rant over,, hope it helps to explain the issue.

If you do not use the loop and you are not keen on working inside amps then just get a short loop lead (the short pedal board leads are ideal)  Leave it permanently looped as that bypasses the internal switch and you can still use the loop if needed. :tu:
Phil.
« Last Edit: May 09, 2016, 09:49:17 AM by phatt »

Bakeacake08

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Re: Crackling noise from Peavey Valveking 100
« Reply #12 on: May 09, 2016, 09:38:01 PM »
"They don't make 'em like they used to," as they say. Of course, they also used to cover houses with lead-based paint, so I guess we might have to take the good with the bad? The good news is the the amp is all sewn up and ready to go home. After hearing Phatt's explanation and seeing the jack for myself, that's definitely where I'm going to start next time I come across (non-musical) funky noise coming from an amp. Thanks to everyone for your help!

g1

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Re: Crackling noise from Peavey Valveking 100
« Reply #13 on: May 10, 2016, 09:13:25 PM »
The switching jack issue is a common fault in more than just guitar amps, mixer insert points are another spot they are commonly used.
The following article goes into more detail, I'll post it here but if someone thinks it would be better somewhere else, please repost it.

 

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