The Acoustic Guitar Forum

Go Back   The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Acoustic Amplification

Reply
 
Thread Tools
  #1  
Old 02-13-2019, 01:13 PM
raduray raduray is offline
Registered User
 
Join Date: Nov 2017
Posts: 106
Default Loudbox Mini just did a strange thing

My wife and I were hanging around and all of a sudden we heard a low frequency hum/rumble in the background. After looking around for a bit, it turned out to be the Loudbox Mini. It was plugged into the wall, but turned off, and there was nothing plugged into the inputs. The hum went away when I turned the power switch on, and then stayed quiet when I turned it off. Weird.

Now when I turn it on, with the master volume turned all the way down, I hear the hum for an instant and then quiet. Can't remember it doing that before, but not sure.

Still works fine with my guitar.

This is lightly used unit and I've had it less than a year. Any idea what's going on?
Reply With Quote
  #2  
Old 02-13-2019, 01:16 PM
jonfields45 jonfields45 is offline
Registered User
 
Join Date: Jun 2011
Location: Allentown, PA
Posts: 4,598
Default

No clue! But when you figure this one out let us know. Calling Fishman is usually a pleasant experience.
__________________
jf45ir Free DIY Acoustic Guitar IR Generator
.wav file, 30 seconds, pickup left, mic right, open position strumming best...send to direct email below
I'll send you 100/0, 75/25, 50/50 & 0/100 IR/Bypass IRs
IR Demo, read the description too: https://youtu.be/SELEE4yugjE
My duo's website and my email... [email protected]

Jon Fields
Reply With Quote
  #3  
Old 02-13-2019, 01:32 PM
DownUpDave DownUpDave is offline
Registered User
 
Join Date: Feb 2018
Location: Pickering ON, Canada
Posts: 1,524
Default

Try plugging it into a different outlet in a different room. My Martin 000-15M has a LR BaggsM1 magnetic sound hole pickup. If my Fishman Loudbox mini is in the basement the pick up makes a humming sound. When I take it up stairs and plug into any other outlet and no issue. My basement is probably haunted

Last edited by DownUpDave; 02-13-2019 at 06:01 PM.
Reply With Quote
  #4  
Old 02-13-2019, 01:35 PM
raduray raduray is offline
Registered User
 
Join Date: Nov 2017
Posts: 106
Default

Quote:
Originally Posted by jonfields45 View Post
No clue! But when you figure this one out let us know. Calling Fishman is usually a pleasant experience.
So I just talked to Fishman. They told me the short noise/hum at turn on is not abnormal, but as to the low frequency hum when turned off, he's never heard of that happening. He just suggested I monitor the situation.

Maybe I should just leave it unplugged when not in use.
Reply With Quote
  #5  
Old 02-13-2019, 01:41 PM
6L6 6L6 is offline
Registered User
 
Join Date: May 2011
Location: San Francisco, CA
Posts: 5,506
Default

Change outlets as suggested above and see what happens.

If I plug any amp into an outlet in my garage I get a lot of hum. But nowhere else in my home.
Reply With Quote
  #6  
Old 02-13-2019, 02:35 PM
raduray raduray is offline
Registered User
 
Join Date: Nov 2017
Posts: 106
Default

Quote:
Originally Posted by 6L6 View Post
Change outlets as suggested above and see what happens.

If I plug any amp into an outlet in my garage I get a lot of hum. But nowhere else in my home.
But does that happen with the power switch in the OFF position?
Reply With Quote
  #7  
Old 02-13-2019, 07:36 PM
Marty C Marty C is offline
Registered User
 
Join Date: May 2015
Location: North Carolina
Posts: 1,223
Default

Strange. I have a pickup that picks up a radio station.
Reply With Quote
  #8  
Old 02-14-2019, 08:53 AM
Big Band Guitar Big Band Guitar is offline
Registered User
 
Join Date: Mar 2017
Posts: 1,031
Default

There may be circuitry that mutes the output when the unit is turned on until the power supply is up and stabilized.

Once it fails permanently then you can send it to Fishman for repair.
__________________
"My opinion is worth every penny you paid for it."

"If you try to play like someone else, Who will play like you". Quote from Johnny Gimble

The only musician I have to impress today is the musician I was yesterday.

No tubes, No capos, No Problems.
Reply With Quote
  #9  
Old 02-14-2019, 06:54 PM
MarkF_48 MarkF_48 is offline
Registered User
 
Join Date: Dec 2010
Posts: 565
Default

Only thing I can think of is the power switch may have had some sort of temporary problem with the contacts, maybe not fully opening when supposedly 'OFF' or some sort of contamination that may have caused a partial power condition which resulted in the amp hum. Does the switch have a definitive snap/click when put to ON or OFF?
This is a standard LB mini and not the Charge model with a battery, correct?

You could get a Kill A Watt electricity monitor and see if there is any leakage current going into the amp when it's off. There shouldn't be, but electrons sometimes do strange things.
https://www.amazon.com/P3-P4400-Elec.../dp/B00009MDBU
Reply With Quote
  #10  
Old 02-14-2019, 10:50 PM
raduray raduray is offline
Registered User
 
Join Date: Nov 2017
Posts: 106
Default

Quote:
Originally Posted by MarkF_48 View Post
Only thing I can think of is the power switch may have had some sort of temporary problem with the contacts, maybe not fully opening when supposedly 'OFF' or some sort of contamination that may have caused a partial power condition which resulted in the amp hum. Does the switch have a definitive snap/click when put to ON or OFF?
This is a standard LB mini and not the Charge model with a battery, correct?
[/url]
Standard LB mini. The on/off switch has a positive snap/click.

Here's a thought: The outlet is on the same circuit (same wall) as an outdoor outlet on my deck. We just had some freezing rain. Is it possible that some of the ice melt made its way into the outlet, partially shorting the wires and energizing the neutral power lead?
Reply With Quote
  #11  
Old 02-15-2019, 10:12 AM
Big Band Guitar Big Band Guitar is offline
Registered User
 
Join Date: Mar 2017
Posts: 1,031
Default

Quote:
Originally Posted by raduray View Post
Standard LB mini. The on/off switch has a positive snap/click.

Here's a thought: The outlet is on the same circuit (same wall) as an outdoor outlet on my deck. We just had some freezing rain. Is it possible that some of the ice melt made its way into the outlet, partially shorting the wires and energizing the neutral power lead?
Unless you have really bad wiring that is not possible. Neutral and ground are bonded together at the breaker or fuse box. Also rain water is a very poor conductor.

I think you can rule out house wiring.

I have reviewed the schematic for the mini. It could be the power transformer.

A simple check.

Unplug the power chord

Flip the power switch to on.

With a good ohmmeter check across the Neutral and hot, should be the DC resistance of the power transformer

Check from neutral to ground, should be open circuit, same for hot to ground, any resistance at all indicates a bad primary in the power transformer.
__________________
"My opinion is worth every penny you paid for it."

"If you try to play like someone else, Who will play like you". Quote from Johnny Gimble

The only musician I have to impress today is the musician I was yesterday.

No tubes, No capos, No Problems.

Last edited by Big Band Guitar; 02-15-2019 at 11:04 AM.
Reply With Quote
  #12  
Old 02-15-2019, 12:06 PM
MarkF_48 MarkF_48 is offline
Registered User
 
Join Date: Dec 2010
Posts: 565
Default

Quote:
Originally Posted by Big Band Guitar View Post
Unless you have really bad wiring that is not possible. Neutral and ground are bonded together at the breaker or fuse box. Also rain water is a very poor conductor.

I think you can rule out house wiring.

I have reviewed the schematic for the mini. It could be the power transformer.

A simple check.

Unplug the power chord

Flip the power switch to on.

With a good ohmmeter check across the Neutral and hot, should be the DC resistance of the power transformer

Check from neutral to ground, should be open circuit, same for hot to ground, any resistance at all indicates a bad primary in the power transformer.
From the schematic does the incoming 'hot' leg only go to a fuse to switch or are there other components tied to the hot leg (caps, MOV's, etc) before the switch?

I tried to find a schematic which I wouldn't mind having for my own LB Mini. Could you please post it or PM me with an attachment?
Reply With Quote
Reply

  The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Acoustic Amplification

Thread Tools





All times are GMT -6. The time now is 04:24 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright ©2000 - 2022, The Acoustic Guitar Forum
vB Ad Management by =RedTyger=