LSS mystery solved

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Axe dude

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I had quit using my LSS for gigs because of a problem that was intermittent. I took my amp in to the local Mesa dealer and they swapped out a tube that I had replaced a week earlier. Anyway, that didn't solve the problem.
I spent a lot of time with Mesa's tech support and got nowhere. I was stuck!
Long story short, turns out that it was the speaker! After playing at moderate volumes for a couple hours, the voice coil would catch making it sound like you were using a fast kill switch in and out. Kind of a machine gun effect. I used one of my Mesa ext. cabs and the problem was solved.
Now the amp is out of warranty so I need to buy a new speaker, but at least I have the problem solved.
I've never heard of a problem like this before. "Most peculiar mama"
 
Are you going to have Weber rebuild it, or buy something else. I like the stock speaker in the LSS>
 
I just ordered a Celestion Gold -mostly based on what I've read on this forum.
I guess the speaker wouldn't have been covered under warranty anyway. The speakers only have a 3 yr warranty and my problem started occurring during the 4th year.
I just about went blind researching favorite speakers! I was happy with the stocker, I just hope I made the right decision. I'm extremely happy that I finally figured out what the problem was. Otherwise I would be stuck with a 70 lb. paper weight. I have a Mk IV head with 2Mesa cabs that is all I really need, plus the '79 hardwood MkII combo I bought new that I had Mark B. upgrade. But there is truly something special about the LS Special!
 
Nice work figuring out the issue and good move pulling the trigger on the gold. I'm sure you'll like it. If you don't, PM me. I'll take it off your hands.
 
the problem with your stock speaker is most likely a frayed lead in wire check where the lead in wires are soldered to the mounting terminals - use a multimeter ;-)
 
Back to square one!
I got my new Celestion Gold installed. After a couple hours playing, THE SAME PROBLEM returned.
This time it started with the foot switch. I was using the effects loop and suddenly I noticed the solo function was acting goofy. On channel 1 when I hit the solo button it sounded like I switched to channel 2. On channel 2 when I hit the solo button, nothing happened and the light on the foot switch wouldn't even come on!
I checked the cable and used the dual foot switch from my Mk ll. It wasn't 't a problem with the foot switch.
The amp stuttered badly no matter what channel or power setting.
I even unplugged the footswitch at the amp, it continued to have the same problem!
It's not the tubes. I've gone through all that.

Anybody that has any ideas of what to do to fix this would be very much appreciated.
 
Any way to record what you are hearing?
You say the footswitch does not seem to work, but the audible problem still occurs with footsw unplugged...
I had a bad switch on my Stiletto f.s. The solo one, IIRC. Mesa sent me a new one and I installed it. No problem since, but they can and do go bad.
Maybe you have 2 issues(?). :?:
 
Old BF Shred said:
Any way to record what you are hearing?
You say the footswitch does not seem to work, but the audible problem still occurs with footsw unplugged...
I had a bad switch on my Stiletto f.s. The solo one, IIRC. Mesa sent me a new one and I installed it. No problem since, but they can and do go bad.
Maybe you have 2 issues(?). :?:
Yes, I recorded a video when it was acting up with my iPad.
I don't think I can post it on this site.
I'm calling Mesa's tech folks today.
 
I guess I'm screwed!
I talked to Mesa' tech support and they won't cover my problem.
I got an RA number and I can send it in on my dime.
I told them that it's an intermittent problem, and that It happens when my amp has been played at stage volumes for two or three hours. They said they wouldn't be able to fiddle with it that long.
Now I own a 60 lb. $2,000 paper weight.
 
Whatever the problem is, it can be fixed.
Is there a good tech in your area? Could turn out to be a relatively simple problem and may not be too expensive to fix.
Also you can post the video on YouTube and add a link to it from here. If we could hear it, I, or someone here, may recognize the symptoms and give you a better idea.

Either way, it is a nice amp and worth repairing.
Good luck! :)

PS...you did not say if you had tried swapping all the tubes. Not cheap, I know, but usually an early step in narrowing down the cause. This does not explain footswitch issues (that could be a diff issue), but it is a start.
 
Thanks for your reply Old BF Shred. You're giving me hope!
You won't believe this, but my amp tech was killed in an auto accident two weeks ago!
I just found out about it yesterday. Unbelievable.
I'll try to post the video I took on YouTube with a link.

http://www.youtube.com/watch?v=F-uRCIIAYPE
 
Axe dude, Why not email Mesa and see if you could ship your amp back to the factory for repair. For instance it cost only $20 to ship it from Galesburg, IL and labor was reasonable with no second guessing. It is their product so no trouble shooting waste and it improves their product to see how or why. I only sent the chassis and removed and bubble wrapped the tubes.
 
I put the chassis back in the cabinet and tried it out. Immediately the amp was doin' it's thing. I could make it stutter just by tapping the standby switch!
I took the chassis back out and just plugged it into another cab. It wouldn't do the same deal.
I guess I'm going to send it back to MB to get it fixed. I just hope they can figure it out.
I'll just end up with another 2-3 hundred dollars into the **** thing.
 
Sounds like it could just be a bad standby switch. If you intermittently loose voltage to the output tubes it will sound like the video, for sure.
And if that is it, it should be easy for them to duplicate and switches are cheap! :wink:
Either way, you know it will be in good hands now. You will get back a perfectly working amp!

And...sorry to hear about your tech. :(
 
I'll post back when I get the amp back from MB.
They said it would be about 2-3 weeks before they could get to it.
I've fought with this problem for almost 4 years now.
By the way, does anyone know what the long black screw that goes through the chassis is for? It looks like something to stabilize the chassis to the case, but it's kind of a funky deal.
 
Thanks Single Recto. I guess I need to spend more time surfing this site!
Anyway, when I get the amp back I plan to buy some aluminum tape and put a small piece where the screw has chewed up the aluminum.
It still seems cheesy though. There should be a permanently welded nut or something on the top of that screw.
 
Axe dude, my sentiment exactly, but the repair was very reasonable. They will figure it out. The made the amp. Let us know what you think when you get it back?
 

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