Burned up my Walkabout?!

Colonel Monk · #1 11-02-2010, 10:04 AM

Hey Guys:

In a spectacular mixture of success and failure, my walkabout failed me at a gig saturday night.

On wednesday, I got my newly acquired Scout 15 to pair with my WA12 combo. 2 ohms. Proved it out at practice on Wednesday night, playing gain at 1 and master at noon for about 4 hours. It was loud, proud, and sounded GREAT. I was in tone heaven, with my walkabout tone finally having the bottom I had been missing.

Saturday, I'm playing at much lower volume - say gain at 1 and master at 9-9:30. Again, sounding just awesome.

We had noticed it was warm on stage - drummer was sweating and seems though the doors and windows were open, the heat was on, and there was a heating duct blowing 140 degree air into the back of my Walkabout! Damn!

So, after the 5th song in our set, it dies on me at the end of Cold Shot. Gone, then came back, but at 20% of the volume. It smelled a bit funny (uhoh) and when I tried turning the volume up, it just wasn't there.

Any idea what might have happened? I thought with thermal protect it would have clicked out before damage occurred? It's happened to me on my Mp600 but it was always normal when it came back on.

Didn't want to run 2 ohms, but as I had a pending trade for another walkabout head I figured at lower volume I could pull it off, especially when it worked the other night (but that room was probably 65 degrees). My plan is for each 4 ohm cab to have it's own amp.

Luckily, I had my MP600 in the car and was able to finish the gig in style with the single Scout 15.

All in all, it was a great gig, even with some drunk chick falling on our guitar players mic stand and bending knobs on his effects with her fall. Good Times..

naturalkinds · #2 11-02-2010, 10:16 AM

Awww, shucks. Reinforces my plan to get a whole other cabinet altogether when I need more firepower. My Scout is 4 ohm.

Best of luck in the diagnosis and repair.

Matt Dean · #3 11-02-2010, 10:21 AM

My amp died during a gig this past Saturday too. Bummer!

ghiadub · #4 11-02-2010, 10:27 AM

THat is a bummer.
My scout has run all day, in the sun @ 102 degrees F, at full volume (halfway on master) @2ohms and never had any issues. I run it thru 4x 8ohm bag end cabs.

I don't run it like that all the time, but it has run fine at full volume for well over 20 gigs @ 2ohms. I mostly run 2x bag end S-15s.

It slays.

BassmanPaul · #5 11-02-2010, 10:46 AM

IIRC the Walkabout has a 4Ω minimum. If so, running it at 2Ω is just asking for trouble IMO.

billfitzmaurice · #6 11-02-2010, 10:56 AM

Quote:

Originally Posted by Colonel Monk

Any idea what might have happened?

This:

Quote:

there was a heating duct blowing 140 degree air into the back of my Walkabout!

You should have moved your amp or shut off the duct. Might not have helped, couldn't have hurt.

Colonel Monk · #7 11-02-2010, 11:02 AM

Quote:

Originally Posted by BassmanPaul

IIRC the Walkabout has a 4Ω minimum. If so, running it at 2Ω is just asking for trouble IMO.

Sorry Paul. It's minimum 2 ohms, and there are more documented successes than failures.

CM

Colonel Monk · #8 11-02-2010, 11:04 AM

Quote:

Originally Posted by billfitzmaurice

This:

You should have moved your amp or shut off the duct. Might not have helped, couldn't have hurt.

Yes, but it had already died before we realized the heat was on. I didn't see the heating duct because it was at floor level in the wall behind a curtain.

I know what happened, I just don't know *what* happened. As in, what do y'all think is damaged.

The amp still makes clear sound, but at about 20% the previous volume.

naturalkinds · #9 11-02-2010, 11:05 AM

Quote:

Originally Posted by Colonel Monk

Sorry Paul. It's minimum 2 ohms, and there are more documented successes than failures.

CM

Sorry Colonel. Documented successes don't entail recommended operation. RTM. Fellow Walkabout owner here. Anyone who owns one and reads the threads knows that even if it's not objectively risky in practice, it's no longer formally recommended by Mesa.

JimmyM · #10 11-02-2010, 11:30 AM

ya, i just read a post on here where they told a guy to get an 8 ohm cab so his walkabout would run at 2.67 ohms instead of two because they were getting too many walkabouts back for repair.

BassmanPaul · #11 11-02-2010, 11:50 AM

The Mesa website implies that 4Ω is the minimum. If guys are getting away with running at 2Ω that's a testament to the amps conservative design but will probably vary from unit to unit and case to case.

This brings up, again, the question of why so many bass amps cannot handle a 2Ω load when just about every stereo power amp can? My cabinets are all 4Ω and all my amps are capable of operation at 2Ω. Running a pair of 4Ω cabinets is not a strange concept by any means.

RickenBoogie · #12 11-02-2010, 11:52 AM

Yeah, though many have gotten away with it, and I mean many, it's still not a good idea. I've done it too, but not anymore. 4 ohms is the norm, and 2.6 is extremely rare for me. 2 is right out. Not that it helps the op, but I'd just take it in for a looksy by an authorized mesa tech. best of luck.

lomo · #13 11-02-2010, 12:03 PM

Seems like a perfect storm-2 Ohm operation and direct placement under a heating duct.
Bummer. There has to be an assumed risk to exceeding the factory recommendations. I'm surprised about the recent post of Mesa sales staff recommending 2.7 Ohms.....but then again I'm not at all impressed with the rest of the advice that went with that suggestion, either (stacked 4 and 8 Ohm Scout 12s). My 1st choice would be 2 8 Ohm cabs, even though I'm one of the many who has logged long hours at loud volumes with my WA heads (I've had 3) running at 2 and 2.7 Ohms with no hiccups, due to the cabs I happened to have on hand.

billfitzmaurice · #14 11-02-2010, 12:27 PM

Quote:

Originally Posted by BassmanPaul

This brings up, again, the question of why so many bass amps cannot handle a 2Ω load when just about every stereo power amp can? My cabinets are all 4Ω and all my amps are capable of operation at 2Ω. Running a pair of 4Ω cabinets is not a strange concept by any means.

The problem lies with the consumer as much as the supplier IMO. Uninformed consumers want to 'get all the watts out of my amp', so they've made the 4 ohm cab the most popular configuration. But then you can't run two cabs with a four ohm rated amp, so the manufacturers apply a 2 ohm rating to amps that in many cases are marginal when actually run at 2 ohms. Mesa could have avoided the problem in this case by making the internal speaker 8 ohms, but that runs up against that 'I need all my watts' mindset.
Pro-sound amps that can run to 2 ohms are a relatively recent arrival, and the reason for them...as well as series bridging, which is almost totally useless...is customer and marketing department demands for ever higher power numbers.

Colonel Monk · #15 11-02-2010, 03:02 PM

Hey guys

I'm not trippin'. What can be broken can be fixed, normally....

Again, I know what happened - bleeping heater duct was pumping air 70 degrees hotter than you'd like right into the cooling tunnel of my amp. That and the 2 ohms burned it up. Both things.

I'm more curious if anyone else has had an issue, what did it turn out to be, and what it might cost to repair.

The "told ya so" stuff isn't all that helpful. I did do my research, The manual that I have says 2 ohms is minimum as does the silkscreen, and most of the people here who do it say if you keep volume under noon it's fine. I was running it at only 9 or 9:30 I really haven't seen alot of posts indicating it's been a problem. I tested it out myself and it worked fine for longer than a gig - till the heating duct incident.

If a few people out there have had an issue like this, that pretty much explains why Mesa downplays it now. They don't want to back pedal and say you *can't* do 2 ohms and be responsible for failures so they *encourage* you to run at 4 ohms when possible.

I have another Walkabout head on it's way to me - my intent is to run both amps at 4 ohms in a slave config. After I get it repaired I'll give it a try.

ishouldbeking · #16 11-02-2010, 03:18 PM

Quote:

Originally Posted by JimmyM

ya, i just read a post on here where they told a guy to get an 8 ohm cab so his walkabout would run at 2.67 ohms instead of two because they were getting too many walkabouts back for repair.

That'd be me, yessirree. The Mesa store didn't say they were getting too many back per se, but that it'd happened a couple of times over the years. More of a "you can do 2 ohms if you really want, but it's on you, bub". In hindsight I'm kind of wishing I had gotten an 8 ohm combo... maybe i'll give em a ring this afternoon.

lomo · #17 11-02-2010, 05:06 PM

Quote:

Originally Posted by ishouldbeking

That'd be me, yessirree. The Mesa store didn't say they were getting too many back per se, but that it'd happened a couple of times over the years. More of a "you can do 2 ohms if you really want, but it's on you, bub". In hindsight I'm kind of wishing I had gotten an 8 ohm combo... maybe i'll give em a ring this afternoon.

Perhaps try to get em to send you an 8 and take the 4 back in the same box. Otherwise a new 8 is about 140 shipped from them.

carlos840 · #18 11-02-2010, 07:52 PM

I use my scout at 2 ohms daily and never had an issue!
The only time i had a problem i was running it on its own at 4 ohm, i had stuffed my coat behind my amp not thinking about the vent and in the middle of our second set the amp just cut out...
Light was still on, tubes where still bright but no sound, after a few seconds it came back but cut again soon.
I just plugged straight into the desk and carried on, its only the next day that i realised it was working fine and assumed it must have been cutting because of heat! (the club was so warm i was literally pouring with sweat, and im sure my poor amp didnt appreciate having its air vent blocked!)
Since then i never had another issue and im always careful not to obstruct the air vents...

All that to say that im surprised your amp didnt go in protection mode like mine did!

D.A.R.K. · #19 11-02-2010, 07:58 PM

i've had 3 walkabouts, ran the crap out of all 3 at 2 ohms and never had a single issue.
just curious, which issue is it (what color stencil?)
looking to get a fourth...

**Freddels** · #20 11-02-2010, 08:26 PM

Have you tried to run it again? The manual states this:

The optimum speaker load for your WalkAbout is 4 Ohms. You may use a cabinet (s) of a higher rating safely (8 Ohm) with no degradation in tone, however the amplifier will not produce its full rated wattage. Minimum load rating is 2 Ohms and while the WalkAbout will handle this lower load condition - and in fact produce more than its rated power, it is not recommended. Prolonged use of a 2 Ohm load will cause the power mosfets to run hot causing the protection circuit to trigger and mute the output signal until such time as the mosfets can return to a safe operating temperature. Avoid using 2 Ohm loads whenever possible.