My wife has an SWR SM900 bass amp that I screwed up the other day. I
unplugged the cord from the bass while it was still hooked up to the
amp. I'm not a guitar/bass player, but I still should have known
better. Anyway, in addition to slightly electrocuting myself, some
nasty sounds came out of the amp/cabinet. Now when using the amp, it
hums fairly loud whenever you're NOT touching a metal surface on the
bass (the strings or knobs, namely). As long as you ARE touching some
metal, the humming immediately stops. So it would appear to be some
sort of electrical grounding problem. I can only assume that this is
happening because of my bonehead accident. (we also just moved into a
new house and hadn't used the amp previously in the new house, so I
can't say for sure whether what I did caused this problem) Can anyone
speculate what I might have done to the poor amp? Is there a way to
fix it other than taking it to an expensive repair shop? If I do have
to take it to a repair shop, can you tell me what might need to be done?
(as a second opinion to what the guy who will charge me money says) |
Request for Question Clarification by
sgtcory-ga
on
04 Dec 2003 12:33 PST
Hello lazytiger,
What kind of bass guitar is it? It may simply be the pickups on the
guitar itself. It definitely sounds like a grounding issue, we just
need to narrow it down to where the problem is. Does the amp plug have
a grounding prong?
Thanks,
SgtCory
|
Clarification of Question by
lazytiger-ga
on
04 Dec 2003 12:56 PST
I've already tried using a different cable and bass, and the problem
still persists. So it appears definitely to be the amp. The amp does
have a grounding plug and it is plugged into a surge protector that is
in turn plugged into a three-prong wall outlet. The surge protector's
"protected" light is on, which would lead me to think that it is
grounded properly. No? Hmm... I think perhaps there is a "grounded"
light on the surge protector as well. If so, I don't recall whether
is is lit. Or maybe it's a "fault" light. I can't remember.
I'm not a home right now unfortunately, so I can't give more
specifics. I will clarify further as soon as I can. Do you have any
more insight based on just this info?
|
Request for Question Clarification by
sublime1-ga
on
04 Dec 2003 16:57 PST
lazytiger...
The biggest problem with unplugging an instrument while
the amp is turned on/up is the possibility of blowing
the speakers. I doubt that it would account for a sudden
'ungrounding'. As for researchone-ga's comment, I've never
known dimmers to cause a problem with hum *unless* the
amp is ungrounded. Grounding should eliminate all problems.
What strikes me is that you included the fact that you
just moved into a new house. It isn't all that uncommon
for the wiring to be reversed in a house, which would
cause what you're talking about. I don't know the
procedure, but an inspector that specializes in checking
out houses before they're bought, or a wiring contractor
should have an instrument that allows them to check the
polarity of the wiring to see if it's up to code.
I'd suggest looking into this. A simple test you can do
prior to that is to take the amp to another house,
preferably one where you know that amps do, or have,
worked correctly. If it doesn't hum there, your house
wiring is the problem.
Let me know if this helps.
sublime1-ga
|
Clarification of Question by
lazytiger-ga
on
04 Dec 2003 21:10 PST
OK, I moved the amp to a different outlet and the buzzing/humming
problem stopped. The surge protector I'm using has a "grounded"
light, and I walked around and plugged it in to a bunch of differnt
outlets in the basement (it's a finished basement). On some outlets,
the light didn't light up at all. On others (like the one I
originally had the amp plugged in to), it lit up only dimly. On still
others (like the one I have the amp plugged in to now), it lights up
fully. So that's one mystery solved - the wiring in this house isn't
great.
There's still one more problem, though. There's a bad popping noise
when you touch metal parts on the bass (it did this before too, but it
seemed a more minor problem when the buzzing was happening). Now
though, it seems to be very particular to touching the pick guard
screws. Is this still just an electrical problem? Do you think
there's really anything wrong with the amp? Should I be calling an
electrician for the house rather than lugging the amp to the repair
shop?
|
Request for Question Clarification by
sgtcory-ga
on
05 Dec 2003 06:03 PST
Hello,
It's still seems like a grounding problem.
I probably don't need to tell you that it's hard to troubleshoot
anything without having the item in front of you. Here is what I
suggest :
1) Take the amp to your local music store.
2) Plug it into a floor model amp. Tell the guys you want to see what
'your' bass sounds like through the amp you are interested in. I
always do this before buying an amp.
3) If you still get the popping noise, then you may want to look into
the grounding of the pickups, or the jack on the amp itself.
4) Only after you have eliminated the bass and the amp would I
consider calling an electrician. (Save yourself money! ;-)
If you can do the above, or have access to a friends bass, let us know
the outcome. This will help narrow down the problem considerably.
SgtCory
|
Clarification of Question by
lazytiger-ga
on
05 Dec 2003 07:10 PST
That sounds like a good suggestion. I will have to try the amp
somewhere outside the house, perhaps a store. You guys have helped as
much as you can through Google Answers. No one's actually answered
the question yet, though! Somebody should get the $10.
|
Request for Question Clarification by
sublime1-ga
on
05 Dec 2003 16:54 PST
lazytiger...
"No one's actually answered the question yet, though!
Somebody should get the $10."
I think we've been waiting for your feedback to see
who was on the right track. Since my response about
the house wiring has led you to some experimentation
which seems to have resolved the humming/buzzing
problem, which was the original topic of this
question, I'd be delighted to step up to the plate
and post an official answer to this question.
If you're inclined to reward sgtcory-ga, the only other
official researcher on this question who can accept
payment, you could open a new question, with his name
in the 'subject' field, for whatever amount you feel is
fair.
Let us know your wishes.
sublime1-ga
|
Clarification of Question by
lazytiger-ga
on
05 Dec 2003 19:34 PST
Both of you helped out. To be fair, I'm splitting the $10. sublime1,
you can answer this question and take the $5. sgtcory, I'm opening a
new "question" with a $5 price that you can claim.
Thanks guys. Sorry my method was a little convoluted. This is the
first time I've actually posted a question on GA. This was really
sort of a forum problem by nature rather than a simple Q&A. I'll try
not to do that again!
Thanks again.
|
lazytiger...
I'll repost here what I said which resulted in the
resolution of the hum/buzz problem with your amplifier:
The biggest problem with unplugging an instrument while
the amp is turned on/up is the possibility of blowing
the speakers. I doubt that it would account for a sudden
'ungrounding'. As for researchone-ga's comment, I've never
known dimmers to cause a problem with hum *unless* the
amp is ungrounded. Grounding should eliminate all problems.
What strikes me is that you included the fact that you
just moved into a new house. It isn't all that uncommon
for the wiring to be reversed in a house, which would
cause what you're talking about. I don't know the
procedure, but an inspector that specializes in checking
out houses before they're bought, or a wiring contractor
should have an instrument that allows them to check the
polarity of the wiring to see if it's up to code.
I'd suggest looking into this. A simple test you can do
prior to that is to take the amp to another house,
preferably one where you know that amps do, or have,
worked correctly. If it doesn't hum there, your house
wiring is the problem.
In regard to your method of resolving payment, it was
fine, even for an experienced user. Computer problems
often present a similar situation, in the course of
which several researchers will pitch in, hesitant to
post an answer with confidence that their solution is
sure to resolve the problem. Troubleshooting at a
distance, by its nature, requires some trial and error.
It's been my privelege to work with you, and I look
forward to your next question.
sublime1-ga |
