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Bass volume drop out


dmccombe7
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Was rehearsing today with my Jazz into Mesa Mpulse and Mesa SW210/115 cabs. After about an hour i heard the volume drop out once or twice. Not completely off but quite noticeable even the drummer heard it.

After a break for food with the amp being switched off for about an hour I changed bass and played another 6 or 7 songs with my P bass and never noticed it again. That points to the Jazz bass having a problem.

Anyone ever experienced that with a Jazz bass and any pointers what it might be. ?

My thoughts :-

Pick up breaking down.

Cable fault on bass.

Dodgy pot on bass.

 

If not the bass any thoughts with the bass rig would be helpful.

Dodgy speaker cable altho they are top quality ones. ?

Tube failing under loads ?

Amp fault somehwre. ?

 

Dave

Edited by dmccombe7
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7 hours ago, Doctor J said:

Did you try the Jazz again after the break?

 

It's more likely something getting hotter than it should in the amp. Turning it off for an hour would have let it all cool.

Didn't have enough time to try the Jazz again but will fire it all up today at home and see what happens but wont be able to try at same volumes.

Will check all tubes are seated properly or might just swap them over with some spares i had for my Ampeg SVT3.

 

Not sure how to check a bass pick up for a breakdown.

 

I'll replace the speaker cables too just in case one of them was starting to go. 

 

Luckily enough i bought a back up amp just in case i had any issues with the Mesa as its getting a bit old now.

I have a Blue Angels biker gig on Sat night and would rather use the Mesa as it has more depth.

 

I've contacted Ghostbusters just in case of poltergiest issues @ambient😂

Dave

 

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Dave,

 

To check the issue, just change things one by one, not all and everything at the same time. 😉 

 

To me, it sounds like a dry solder in your amp which is a nightmare to isolate, so the best thing to do is redo all solders.

 

That said, just checking around the voltage lowering resistors might be a very good start as it often starts there.

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10 minutes ago, Hellzero said:

Dave,

 

To check the issue, just change things one by one, not all and everything at the same time. 😉 

 

To me, it sounds like a dry solder in your amp which is a nightmare to isolate, so the best thing to do is redo all solders.

 

That said, just checking around the voltage lowering resistors might be a very good start as it often starts there.

If its internal amp issue i'll take to a pro as i'm not confident enough to tackle that type of work.

 

I think you might be right tho as i had similar issues with my Ampeg SVT3 with soldering issues and cracked tracking on the circuit board.

The thing that's throwing me a bit is that the P bass sounded fine but the amp had only been switched on for approx 1 hr with it whereas the amp had been on for several hours when using the Jazz.

 

Dave

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Having done the usual google search i found that this volume drop out can be caused by tube failures altho most lost volume completely but some reported volume drop outs. No idea how old the valves are so might be worth replacing them and see how it goes from there.

The general concensus from most techy backed guys on line reported that Mesa amps generally dont have quality issues with circuitry and soldering etc. Having said that i guess after time any amp can still get soldering problems thru time and just wear and tear.

 

Dave

 

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I've been a touring guitar tech, and I can tell you that Mesa Boogie's do have their shares of issues. And dry solders are some of them...

 

An old valve will compress your sound more and more and more, but they rarely really die, except if there's a break in the glass (or crystal for some).

 

But you can have a loose connection in the socket which happens sometimes

 

If that's the case, don't try to fix it yourself as there's a potential risk of death if the capacitors are still fully charged.

 

That said simply taking the valves out and back in will remove oxydation that can also cause some similar issues.

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Agree with Hellzero regarding possible causes. 

 

From my experience, passive basses don’t usually reduce in volume if there’s a fault, they are either working or not! Same goes for leads - crackling and intermittent on/off but not usually drop in volume.

With active basses then batteries and circuit boards can cause issues like you describe. 

I’d get your amp looked over by a good tech, it seems the most likely suspect.

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Brilliant guys and thanks for help and advice. I will unplug and replace the valves as the amp just in case its that simple. 

I wont tackle anything else in my amps even tho i have a background in Industrial Intsrumentation. 

I'm not good enough to fault find on amps.

I've contacted Westside Distribution in Glasgow which isnt too far from me if they can take a look at it. I think that's who Andy @agedhorse from Mesa recommended on another Mesa post somewhere. 

 

That's good news about the passive bass either working or not. I've been very lucky over the years not to experience any major bass guitar faults when playing. Amps are always a problem especially if 2nd hand but i've got the Mesa TT800 on order and hopefully i wont experience any probs with that when it arrives.

 

Dave

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31 minutes ago, agedhorse said:

Yes, the folks at Westside are excellent, and run a tight ship.

Thanks for getting back to me @agedhorse always appreciated.

They got back to me and said they dont do Mesa gear now for past year. 

I've contacted a guy i've used many times when i owned Ampeg gear and he has worked on several Mesa amps over the years. Taking to him on Tues.

Glasgow Studio Electronics might be worth adding him to your repairers list altho i'm not sure how that all works for Mesa.

The other option was Fretronics who are on your list but got no response from them at all.

I've used GSE many times and happy with his work over past 10 years.

Dave

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