Amp crackling/burning

D

dem466

New member
I have just recently acquired a DSL100MLB (2009 special edition). It's just over a year old, and has had no problems in the past.

Recently I was just playing guitar as usual, and all of a sudden large crackling sounds started to happen. I thought it was an issue with my guitar jack, but after changing guitars and leads it did it again. The amp volume was pretty low, yet the crackling was VERY loud.

From the front of the amp, i could see pulses of light coming through the LEDs on the front plate that were in sync with the cracking sounds. Whether this was from the LEDs them self or from the power amp tubes pulsing, i'm not sure.
This had happened once or twice in the recent past, but stopped pretty quickly so i continued like normal.

Shortly after the crackling sounds started i could smell something burning from the back of the amp, most likely electrical. So i shut it down immediately, but i'm a bit worried about starting it up again until i know what the problem is.

I've done a bit of research, but haven't found much about this. I have thought of two main problems that might have caused it. One would be the speaker cables and impedance load. I always check regularly that the cables are properly connected any everything, so i've ruled it out has human error.

The other thought was that maybe it was one of the power tubes. I'm looking into replacing them now, but i'm not sure if they are the main problem. Is it possible for a power tube to blow/stop working?

Any help with this would be appreciated.
 
Probably, but not certainly, the power supply. Look inside and see if anything looks overheated esp the mains transformer, unless it has a switching power supply. Really you need to check the high voltage supplying the tubes, if it's low or fluctuating that's the problem
 
Most obvious thing to do is completely retube it. ECC83 = 12AX7. Get all new, as you should do after buying ANY used amp. You dont really know what the previous owner did to that amp, might have left it on with no speaker plugged in, might have left it on while on vacation, might have run it with a different cab that wasn't matched correctly, etc.... There are many reasons power tubes will fail, and that is the most likely most obvious place to start. If you retube and turn it on and the same thing happens, shut it off, put the old tubes back in and start looking for an amp tech. Best bet, if necessary, might be to ship it back to an Authorized Marshall repair center, and these days even that is no guarantee. These are not the Marshall amps of yesteryear....

Not trying to be crude here, but........ the real right answer is to never buy a Korg Marshall amp. Sorry.....

Make sure you get good tubes, dont just get the cheapest chinese shot glass tubes you can find. You didn't relaly say what you had it plugged in to. Was it a properly matched cab? Like 8 ohm jack into an 8 ohm cab? Does the amp have a jack for connecting an external speaker cab?
 
I think after 2 days...that MOFO either burned up....or he fixed it and is too busy happily playing it to post back. :D
 
with any electrical equipment...

as soon as I start hearing pops and cracks, and seeing "ARCS" as you describe...

I start thinking...

1) electrical short, or bad connection (arcing)
2) lamination going on the main power supply transformer, maybe
3) one oro more big capcitors in the PS sh!t the bed...

on a hunch and nothng more, I cant recall a bad high voltage POWER TUBE (or even a smaller tube...) causing arcing...

could be something as silly as a "cold" solder joint gave out, and the wire moved around and decided to ground out and make the little lightning bolts (arc-ing)

if you know what NOT to TOUCH, get in there, with the power off, and nebsh!t around... arcing leaves a visible clue trail a mile long, so you can identify most (maybe all...) components that sh@t the bed... I like to get in there IMMEDIATELY if it happens in front of me, so I can use my eyes and nose to see/smell which components are smoking, where the heat is coming from...

big transformers get expensive quickly with increasing size...
 
You must log in or register to reply here.
Back
Top