Towards the end of the first set of my gig last night my Marshall combo packed in.
It was making a God-awful loud buzzing sound intermittently which I thought may be due to a dodgy lead or bad FX pedal lead connection.
I gradually removed my pedals between songs, in case that was the issue - until the guitar was plugged directly into the amp. I then tried a different guitar and it still persisted.
The noise got worse and worse as the night went on until it was buzzing all the time and that was the end of it!
I've tried the amp again today and it's doing exactly the same thing.
Here's a video of it happening (the problem occurs around 20 seconds in) :
Any techs able to diagnose the problem?
I've had the amp from new and used it extensively over the last couple of years, so could it be a failed valve?
Any help much appreciated!
Cheers
Comments
First, remove one of the EL34s and test the amp - if the problem has stopped, the fault is in the one you've taken out. If not, replace it and remove the other one, and repeat. It's safe to operate a fixed-bias amp temporarily with one valve missing, although it won't sound good at higher volumes with a guitar through it.
If it's not either of the power valves, replace the preamp valves one at a time with a known good spare.
If it is a power valve you should replace both of them, but keep the non-faulty one as a spare, it may be useful...
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Removed an EL34 played for 10 minutes without any problems so obviously thought that must be the culprit.
I thought I'd put the valve back in, just to confirm so I did and played for half an hour with no problems at all!
I suppose I'lI have to try again tomorrow night.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Forgot to mention I also tried putting the amp on maximum volume with nothing plugged in and tapping the valves - all seemed fine there.
Think I'll try leaving the amp powered up for half an hour or so tomorrow evening to get the valves cooking, then giving it another blast.
Very infuriating!
Further investigations identified a problem with the PCB at the valve base for V2 - the amp tech re-soldered it.
I'll try it out when I'm next gigging near to home!
I loved by DSL, but had no end of problems due to solder and the PCB, eventually sold it on pretty cheap.
annoyingly couldn't ever replicate the faults when trying to find them, only when at a practice or gig! (even if I had it at home running all day to warm it through)
mine was a 1999 DSL100 head, was on its second PCB when I got it 2009.
Slightly worrying that you’ve had solder joint issues with yours, but to be fair that’s not unknown with most amps.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
If not, and you were using it at either 4 or 8 ohms, there's a switch in the 16-ohm jack on the amp which also does that with the same result. Very stupid design - and if you test the amp at 16 ohms, it doesn't show up.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein