Alesis Microverb III -- Loud Hum all of a sudden!
Lovguitar
a rack in my recording rig, suddenly began to make a loud humming
sound. Sounds like a bad cable but continues to make the sound
without cables -- the unit itself is making this noise. It does it
with the input turned down and the "level light" is red on most
settings (it's usually green).
I swapped out a power supply with same results. Any thoughts as to
what would make this critter act this way?
Thanks,
Paul
RS
<lovg...@aol.com> wrote:
>Without warning or provocation, my Alesis Microverb III, which sat in
>a rack in my recording rig, suddenly began to make a loud humming
>sound. Sounds like a bad cable but continues to make the sound
>without cables -- the unit itself is making this noise.
That's very Zen, Paul. How do you know if it's making noise if it's
got no cables plugged in? Going by the indicator light?
> It does it
>with the input turned down and the "level light" is red on most
>settings (it's usually green).
>
>I swapped out a power supply with same results. Any thoughts as to
>what would make this critter act this way?
You'd probably have a jack that grounds the input when nothing is
plugged in. Any chance that pressure on a jack or something pulled up
circuit board traces for the input's ground connection?
Does signal still get through? How loud is the hum compared to
signal?
Try this as an experiment: Plug into an output jack or another jack
with good ground. Jumper the ground on that cable to the ground on
the input cable. Of course there are several ways that the ground
could disconnect, if it's even the ground connection. So that's a long
shot.
Also, the wall wart supplies AC, so if something went out in the
supply filtering, that could also do it. Probably lots of hum and
little or no signal in that case.
The good news is that you should be able to find a replacement for
under $100.
RS
>
>Try this as an experiment: Plug into an output jack or another jack
>with good ground. Jumper the ground on that cable to the ground on
>the input cable.
PS: And try connecting that ground to the input 'hot' pin as well.
RS
>On Mon, 01 Mar 2010 12:22:03 -0500, RS <R...@saynotospam.com>wrote:
>
>>On Sun, 28 Feb 2010 19:19:34 -0800 (PST), Lovguitar
>><lovg...@aol.com> wrote:
>>
>>>Without warning or provocation, my Alesis Microverb III, which sat in
>>>a rack in my recording rig, suddenly began to make a loud humming
>>>sound. Sounds like a bad cable but continues to make the sound
>>>without cables -- the unit itself is making this noise.
>>
>>That's very Zen, Paul. How do you know if it's making noise if it's
>>got no cables plugged in? Going by the indicator light?
>
>Obviously the unit is making a mechanical hum.
That seemed very unlikely. But not impossible. Paul, can you confirm?
Lord Valve
Did it start doing that just as you plugged a cable into it, or when you
touched the rack it's in, or touched another piece of gear that is
connected to it?
And if you're trying to say that the unit itself
is *physically* buzzing - making mechanical
noise, with no input or output cables attached...
since there's no transformer in the unit, it'd
be hard for anything inside it to buzz loudly
enough to be heard through the atmosphere.
More details, please.
Lord Valve
Expert (please obsess)
RS
>I interpret that quote along with "makes the sound without cables" to
>be mechanical noise. Not sure if the Microverb 3 has an internal
>transformer. My Midiverb II units both have external transformers with
>rectifier/regulator located inside.
>
>A bad transformer can induce mechanical hum in surrounding metal.
The Microverb III has a wall wart. Still could be something
internal...it just seems very odd. No reason to have a switching
stepup inside that box, and it's tough to figure what else could be
acting as a transducer.
Lovguitar
>
> - Show quoted text -
OK -- sorry for the miscommunication. The unit is not mechanically
buzzing. It is producing a loud buzzing sound with no input (or with
something plugged in for that matter) when its output it connected to
anything. Very little to no sound signal passes and the buzzing is
WAY loud. The only thing that quiets it is if you turn down the
output pot. I think it's something in the unit's filtering supply, as
the unit uses a wall wart that produces 9volts ac. I don't have a
schemo but I would suspect caps, diodes or something else in the
supply right after the 9v ac input.
I was using the unit for a recording and it worked fine. Went to
bed. The next morning as I walked past the studio I saw that my
Mackie 1604 was indicating a signal. It turned out that it was
getting this buzzing sound from the microverb through the effects send/
return circuits.
The red light stays lit all the time, even with the input cables
disconnected. The red light usually indicates that you are
overdriving the unit although I have read that a constant red is also
an indication that one of the rails is out. I know I can buy another
one for under $100 but money is tight and this is probably a few bucks
worth of components if I do it myself. I can solder just fine and
have built a number of devices, including a 59 deluxe kit and a fender
clone reverb unit. I also make my own guitar cables, stereo cables
etc. and am capable of fixing my tube amps. I'm not as knowledgeable
about the solid state stuff.
Thanks for your help.
Paul
boardjunkie
>
> - Show quoted text -
Check the diodes/caps/regulators in the pwr supply.
RS
wrote:
>On Mar 1, 6:14?pm, RS <R...@saynotospam.com> wrote:
>> On Mon, 01 Mar 2010 13:37:37 -0500, Rednef wrote:
>> >On Mon, 01 Mar 2010 13:26:44 -0500, RS <R...@saynotospam.com>wrote:
>>
>> >>On Mon, 01 Mar 2010 12:37:23 -0500, Rednef wrote:
>>
>> >>>On Mon, 01 Mar 2010 12:22:03 -0500, RS <R...@saynotospam.com>wrote:
>>
>> >>>>On Sun, 28 Feb 2010 19:19:34 -0800 (PST), Lovguitar
>> >>>><lovgui...@aol.com> wrote:
>>
>> >>>>>Without warning or provocation, my Alesis Microverb III, which sat in
>> >>>>>a rack in my recording rig, suddenly began to make a loud humming
>> >>>>>sound. ?Sounds like a bad cable but continues to make the sound
>> >>>>>without cables -- the unit itself is making this noise.
>>
>> >>>>That's very Zen, Paul. ?How do you know if it's making noise if it's
>> >>>>got no cables plugged in?
....
>>
>> >>>Obviously the unit is making a mechanical hum.
>>
>....
>
>OK -- sorry for the miscommunication. The unit is not mechanically
>buzzing.
That's what I thought. And the Zen thing was a joke.
> It is producing a loud buzzing sound with no input (or with
>something plugged in for that matter) when its output it connected to
>anything. Very little to no sound signal passes and the buzzing is
>WAY loud. The only thing that quiets it is if you turn down the
>output pot. I think it's something in the unit's filtering supply, as
>the unit uses a wall wart that produces 9volts ac. I don't have a
>schemo but I would suspect caps, diodes or something else in the
>supply right after the 9v ac input.
You could still try what I recommended: Take a clip lead from a
known-good ground (like the shield on a cable plugged into the output
jack) and touch it to the tip of the input cable. But broken signal
ground probably wouldn't make that much noise. It probably is
something in the supply.
First step is to take it apart to get a look. See if you even want to
work on it. If you do feel comfortable, you could try swapping out
components in the supply section. That should be easy to trace from
the wallwart connector.
If you have a meter on hand, see if you can check both AC and DC
values right where the rectifier feeds the first filter cap.
Then presuming that is the problem, and if you have the parts on hand,
just change out the rectifiers and filter cap. There may be a potted
rectifier bridge, but you can replace that with individual
1n400-whatevers (Radio Shack does stock those).
And swap the main electrolytic(s).
Also you did say "rails" plural, and it may indeed have + and -
supplies, so 2x the above.
You probably know how to do that, but get back if you need more help.
Not that this was anything you didn't expect. And after all this, you
do realize that you could spend money on parts and still not end up
with a working reverb.
Lovguitar
Back then the unit just started making the noise. No provocation of any kind other than turning the unit on -- it's permanently installed in a rack.
This time (2015) when I plugged in the power, the red light stayed constant. I figured it was power supply again. I found a burnt diode right after one of the voltage regulators. I replaced the regulator and the diode and looking at the Alesis service guide I recently purchased, I also replaced e-lytic caps in that side of the rail and another metal film cap they said is often a culprit. I figured while I'm in there I should do it. It's a pain getting it in and out of the rack.
thanks to all those who have taken the time to weigh in on this!
kay.i...@gmail.com
Would you be able to supply some more information as to where you found that information you refer to here?
I have a problem that seems identical.
I would love to know more about the parts you describe, the forum you found the info, and if possible the service manual.
Regards
drhardlove