Amp Gurus...New Marshall DSL 40c Took A Crap. Tubes??

[Old Fart Rocker]

Well my kids got me a new Marshall Dsl 40c for Christmas and I love the amp. BUUUUT...the other day I'm playing at a low volume in the den and suddenly no sound. There was no warning. No pop...no hiss,,,no sudden loud static...nothing. One note comes through just fine, the next note nothing.

Troubleshooting stuff I did:

Switched channels...no difference
Plugged guitar into the return of the effects loop and had sound with no tone or pre amp control
Switched from low power to high power and back, no difference
In high power, maxed gain and volume on both channels...could faintly hear the guitar through both channels...low power couldn't hear anything

My guess is a bad tube, probably v4 which is the PI...I think. I ordered a new set of tubes anyway, but any input would be welcomed. Please let me know your thoughts.

BTW, my wife and kids bought the amp through American Musical Supply. I'm not overly thrilled with their service, and I'm less impressed by Marshall USA. I've called them 3 days in a row and I'm routed to some music dealer. No one answers because "all reps are busy" and your asked to leave a message. 3 messages later and still no return phone call. If anyone has any better contact info it would be much appreciated.

[DeepEnd]

No clue but if you're talking about Christmas 2016 the amp is under warranty. Find a service center and take it in: http://www.marshallusa.com/service.asp. Based on the location in your profile, it looks like your best bet is The Amp Lab in Campbell.

[Old Fart Rocker]

Thanks for the reply. Yeah, I saw that and already called them. Said it was probably tubes. Said I could bring it in, but he has a 4 week backlog. As much as I'm not a GC fan, I'm starting to see the benefit of buying from them. With GC, I could just take it back. Oh well...I'll swap some tubes and see what happens.

[WRGKMC]

Go to the Marshall site and check and see if the warrantee is good at any Marshall dealer. I'd think any dealer would do the work.

From your description it sounds like the issue is with the preamp. It may or may not be a tube. Given how new it is I wouldn't think so. The Chinese tubes Marshall uses aren't the best however.

What I'd do is pull the head and inspect it for cold or cracked solder joints. The head likely uses a PC mount input jack which is where I'd focus my attention. The plastic jacks only need one good tug on the cord and either the jack can be damaged or the solder joint to the jack may be cracked. Whats you hear with the gain cranked is simply a capacitive effect of the signal radiating across and open solder joint.

If its not the jack then maybe its a tube. I'd make sure they all light up. Make sure all the sockets are tight, make sure the reverb is plugged in too.
After that you could swap the preamp tubes around and see if the problem moves. Otherwise you'll need at least one new one to swap out on a rotating basis.

I suspect these newer amps have PC mount tube sockets They too can vibrate and cause weak solder joints to crack. You know your power amp is good because you have sound which also means your power supply is good. You just have an open signal or open short, most likely before the first or second gain stage. Good news is It doesn't sound like its lethal or hard to fix.

[MacFangus]

The newer Marshall stuff doesn't seem to hold up too well. Find an older Marshall, and call it good. The 30th Anniversary Marshall 6100 heads are fine sounding amplifiers, and can be had for a song! Goes from Fender-like cleans, JTM45, Plexi, JCM800/900, to JVM gain tones.

[Old Fart Rocker]

UPDATE****** Turned out to be a tube. V2 to be exact. I ordered a fresh set of tubes. I'll keep the originals as spares. Thanks for the replies!