Please HELP: Problem with GK-MB500 (hiss/flutter)

[shaudenfreude]

Hey guys, I am new here... thanks for all the info on the forums - really helpful. Couldn't find anything related to my problem, so posting, hoping to hear if anyone had experienced anything similar.

I started having an intermittent problem with my Gallien-Krueger MB500. The amp is less than a year old. I use the amp with CX115 cabinet. When the problem is reproduced, it persists when the amp is hooked up to any other cabinets and any other basses, so I narrowed it down to the amp.

Description of a problem:
when any note is plucked on a bass, the sound is accompanied by a very audible hiss that fades away slowly when you let the note ring, but it's prominent with every note. It's especially bad in the higher register, to the point where the sound is cut down half way with the hiss. Hiss resembles a speaker flutter, but the speaker is not fluttering during this.

The problem is intermittent and appears randomly, persisting for a period of time (10-15 minutes) and goes away just as randomly. Sometimes it doesn't come up for days but eventually reappears (again, randomly).

I was able to record the sound during the last occurrence - not sure how to post it here yet

Is there anything I can do to troubleshoot or diagnose this myself?
Would this be a known problem that can be easily repaired/worked around?

Any help is appreciated!
Thanks a lot

 

[eriky4003]

I'd write to GK to see what they can do for you. They may recommend you return to the store you purchased it from in case they are an authorized repair shop. The only other thing I would check is eliminating your bass-to-amp cable to see if that is causing the issue.

 

[shaudenfreude]

I'd write to GK to see what they can do for you. They may recommend you return to the store you purchased it from in case they are an authorized repair shop. The only other thing I would check is eliminating your bass-to-amp cable to see if that is causing the issue.

Thanks, man. Emailed GK techs - let's see if they reply. Yep, tried different cables, basses - all the same. The only good thing now is that the amp has gone into this state permanently - the intermittent thing bothered me the most now I don't need to worry about it crapping out at a gig, will just use a backup for now...

 

[BassmanPaul]

If the amp is less than a year old it should be still covered by warranty. Take it back and get them to sort it out.

 

[Red Planet]

Try a short patch cable in the FX loop (out of send and into return) and see if problem goes away.

 

[agedhorse]

Absolutely work with the manufacturer on this, that's exactly what your warranty is for and I'm sure GK will take care of you. Don't attempt to mess with it yourself.

 

[shaudenfreude]

Hey guys, thanks for all of your replies and suggestions!! GK got back to me with a reply to try out running the bass through the FX Return jack on the back, when the problem is present, and see if the sound has the same issue as when run through a regular input jack to isolate the source of the problem. I haven't had a chance to test the sound through the return jack yet, but I have some new information:

Last time the issue happened (before I got GK's reply), I lifted one side of the amp about one inch and let it go, and that gentle "drop" made the issue go away immediately !! This would mean that something could be loose inside (the whole thing sounds a bit dumb, I know, but it worked ... does any of this sound familiar to anyone? if yes, what could that be and can I possibly address it myself?

Thanks a lot!

P.S.
The problem with getting it serviced for me is that I live in Canada, and the closest authorized service center to me is a 75 miles away (Buffalo, NY), according to the GK site. I am comfortable with light electronic repairs, hence looking to see if it could be something simple that I can troubleshoot myself with someone's direction.

 

[agedhorse]

Do you have a scope and signal generator and know how to use them?

 

[kpc]

Hey guys, I am new here... thanks for all the info on the forums - really helpful. Couldn't find anything related to my problem, so posting, hoping to hear if anyone had experienced anything similar.

I started having an intermittent problem with my Gallien-Krueger MB500. The amp is less than a year old. I use the amp with CX115 cabinet. When the problem is reproduced, it persists when the amp is hooked up to any other cabinets and any other basses, so I narrowed it down to the amp.

Description of a problem:
when any note is plucked on a bass, the sound is accompanied by a very audible hiss that fades away slowly when you let the note ring, but it's prominent with every note. It's especially bad in the higher register, to the point where the sound is cut down half way with the hiss. Hiss resembles a speaker flutter, but the speaker is not fluttering during this.

The problem is intermittent and appears randomly, persisting for a period of time (10-15 minutes) and goes away just as randomly. Sometimes it doesn't come up for days but eventually reappears (again, randomly).

I was able to record the sound during the last occurrence - not sure how to post it here yet
I would send it to a tech.
Is there anything I can do to troubleshoot or diagnose this myself?
Would this be a known problem that can be easily repaired/worked around?

Any help is appreciated!
Thanks a lot

 

[darwin-bass]

Cold solder joint or a loose ribbon cable is my guess. Send it in for service.

 

[shaudenfreude]

Do you have a scope and signal generator and know how to use them?

Nope, don't own any, unfortunately...

 

[agedhorse]

Without a lot of experience and the tools, I wouldn't even know where to point you to start.

It might be best to find a qualified service tech to properly troubleshoot your amp. Once he identifies the cause of the problem, the solution will be MUCH simpler and more effective than just guessing.

 

[eriky4003]

Shaudenfraude, doesn't Long & McQuade service GK? I thought I had a problem with my MB500 which they looked into back in 2012-2013.

 

[shaudenfreude]

Hey guys, a quick update on this for the sake of sharing the info for anyone with the same problem in the future:

GK tech got back to me in response to my description of my "drop" test (see my earlier write-up about it on this thread). His conclusion is that it's the wire harness that causing the problem and it will require replacement.

He also indicated that Yorkville Canada (in Pickering, Ontario) is an authorized service center for GK products in Canada. Yay! I contacted Yorkville, they confirmed, and got I it lined up for a warranty repair with them. Just need to bring it in now.

Thanks a lot to everyone for their help so far. Will post another update once I get it repaired with Yokville.

 

[Red Planet]

Hey guys, a quick update on this for the sake of sharing the info for anyone with the same problem in the future:

GK tech got back to me in response to my description of my "drop" test (see my earlier write-up about it on this thread). His conclusion is that it's the wire harness that causing the problem and it will require replacement.

He also indicated that Yorkville Canada (in Pickering, Ontario) is an authorized service center for GK products in Canada. Yay! I contacted Yorkville, they confirmed, and got I it lined up for a warranty repair with them. Just need to bring it in now.

Thanks a lot to everyone for their help so far. Will post another update once I get it repaired with Yokville.

Excellent please report back!

 

[1bassplayinfool]

Long time GK user here... CS is 2nd to none. I'm sure you will get all sorted out.

 

[Fishheadjoe]

Those Yorkie guys will have you up and running in no time!
Fishheadjoe

 

[heynorm]

Sounds similar to an issue I had about four years ago. Same “drop test” also worked. Dealer fixed. I don’t recall the exact problem but it has been fine since then.

 

[And I]

Drop test, otherwise known as "percussive maintenance". Quite popular in TV repair prior to flat-panel TVs.

 

[shaudenfreude]

Hey guys, a quick update on this for the sake of sharing the info for anyone with the same problem in the future:

GK tech got back to me in response to my description of my "drop" test (see my earlier write-up about it on this thread). His conclusion is that it's the wire harness that causing the problem and it will require replacement.

He also indicated that Yorkville Canada (in Pickering, Ontario) is an authorized service center for GK products in Canada. Yay! I contacted Yorkville, they confirmed, and got I it lined up for a warranty repair with them. Just need to bring it in now.

Thanks a lot to everyone for their help so far. Will post another update once I get it repaired with Yokville.

Hey guys, a quick update: finally made it to Yorkville (in Pickering, ON) to bring the amp in for warranty repairs. It turns out that Yorkville only does warranty repairs for GK products purchased in Canada. Since I bough my amp in the US (as per my bill of sale), I am SOL with Yorkville as far as warranty repairs go. They offered to estimate the repair cost - waiting for that...

I emailed GK to see what my options are here, but I suspect it would come to a choice between paying for repairs at Yorkville or paying for shipping it in to GK in Cali and back to get it repaired under warranty.

If anyone has been in a similar situation, please share some thoughts. Appreciate any info.

Thanks in advance!