Little Mark Tube 800 - no output?

neurotictim · #1 10-01-2010, 03:46 PM

So I just got this Little Mark Tube 800 from WarwickDude68, and I bring it to practice for the first time today, plug it in, get everything together, and I've got no output.

FWIW, I'm confident that when it left Steve's hands it worked fine - he gigged it the night before, in fact.

I'm playing the new Corvette $$ 5 into the LMT800, and then to an Avatar BL410 Neo 4 ohm cab. AI've verified the Corvette's not the problem - played that a bunch in the last couple of days through my Fender Rumble combo.

Plug the LMT800's effects send into the PA, it works. Same deal with the tuner send, and the Line Out works as advertised, both pre- and post-EQ.

I took the top cover off, just to verify nothing came loose in shipping, and noticed that a board-mounted LED lights up red, which in my line of work means there's a failure somewhere. D18 is the component name on the board.

The tube lights up, and I get a definite difference in tone with the blend knob, and all the other knobs appear to work (via the line out).

Anyone have any ideas? I was hoping to have this thing running for my gig tomorrow, looks like I'll be running it direct to the PA, which isn't horrible, but still...

BassmanPaul · #2 10-01-2010, 04:06 PM

Obvious things: try a different speaker cable and check the cabinet with a 9V battery.

craig.p · #3 10-01-2010, 04:30 PM

What Paul said. Also if you're using a cable with Neutrik ends, try one with phone plugs. And if you're using a cable with phone plugs, try one with Neutriks.

Try another speaker cab, too, even if it's not a bass cab. (All you're trying to do is verify power amp go/no-go.) I'm thinking maybe the LM is looking at the Avatar's impedance before it enables the power amp section, and it's saying, "Nope. Ain't doin' that." I admit it's a real long shot, but you've got nothing to lose by trying.

neurotictim · #4 10-01-2010, 06:42 PM

So I tried swapping cables and cabs, no joy. It's definitely the power section.

neurotictim · #5 10-01-2010, 08:32 PM

Okay, I'll claim the dumb*** award here. It's especially embarrassing given my occupation, but I figured it out with a little help.

It was a combination - the master knob is a pull-out mute switch. Little did I know you REALLY have to push in on that sucker to make it un-mute. Unlike the one I tried in GC - probably just needs a bit of a cleaning. The second part of the combination was my cable - it does work, MOST of the time. I've never had any problems with it before, and haven't even moved it for better than a month, but apparently it was just waiting to go - I DID try the LMT800 and cable with one of our monitors - but after using it to plug my guitarist's Line 6 head to his cab, it only worked when laying a particular way. It was just bad coincidence that it worked when I tried it into another cab.

So anyway, long story short I figured it out, there's nothing wrong with the amp that a little cleaning agent won't fix, and I now know I have a bad speaker cable.

At the risk of my pride, I'm going to leave this thread as-is in case anyone else has this particular problem.

lbwdog · #6 10-01-2010, 09:01 PM

While we're all contemplating that Master/Mute potentiometer, I wonder how hard it would be to replace it with a push on/push off type switch.
I always inadvertently move my knob off it's mark when pulling on that switch.

WarwickDude68 · #7 10-01-2010, 10:34 PM

TIM....DUDE! You almost gave me a heart attack, bro!!!

I am so glad that you figured it out. I know how good that feels!

craig.p · #8 10-02-2010, 04:46 AM

Thank you for posting the resolution(s) to the problem.

BassmanPaul · #9 10-02-2010, 06:38 AM

Usually with a modern amp like the MB stuff, if the amp powers on and the relay clicks in to connect the speakers the amp itself is good. I'm glad you sussed out the problem. BTW, don't feel foolish, all of us have done something similar in out lives!

fleabee · #10 10-02-2010, 06:40 AM

Glad you got a happy ending{no pun intended}

**Freddels** · #11 10-02-2010, 08:53 AM

At least you know the mute works well.

neurotictim · #12 10-02-2010, 06:56 PM

Last update - played the gig today (at the ungodly hour of 10am!!!), ran the LMT through the sound guy's Ampeg 810 for backline - mic'd the cab for the FOH.

Sounded absolutely gorgeous, not so much as a hiccup.

http://www.youtube.com/watch?v=l8xiON6TqlQ

(at just after 10am, there were maybe 30 people there, not counting vendors, but it was fun)

WarwickDude68 · #13 10-03-2010, 01:06 PM

now THAT is some beefy tone!