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Trouble with G.K head unit going dead onstage

L

LTDVIPER333

Apr 18, 2009
120
2
Nelson, New Zealand
#1
Hi there people of the undertone!

Plugged in my much loved 2nd or possibly even 3rd hand purchased Gallien-Krueger 400RB which is older than me (manufactured in 1987-or possibly 1988) and it shorted out going completely quiet in the third song of our set.

I happened to be gigging with my band in our small, rustic, local hippie pub know world famously as the Mussle Inn. The 400RB was fine for two songs of the set, but went dead quiet on the third number, despite the red light still registering power.

Took it in to a local music store and the head unit amp was still not producing any sound what-so-ever, through an entirely different cabinet and lead. Bass + guitar lead were fine as I switched to a fender combo amp which proved ok.

Wondered if any one had any ideas whether this could be simply be a fuse gone awol or something more serious?

Cheers
:( :bassist: :bassist: :bassist:
 
#2
Have you tried bypassing the effects loop? If you did a search for GK and issues, that comes up a few times. Also you local amp tech could probably tell you whats wrong with it as it's a bit hard to troubleshoot your amp over a forum.
 
#6
WingKL said:
Have you tried bypassing the effects loop? If you did a search for GK and issues, that comes up a few times. Also you local amp tech could probably tell you whats wrong with it as it's a bit hard to troubleshoot your amp over a forum.
Click to expand...

I had recently purchased a Boss Multi-fx pedal unit, running it via two cables through the Send and Return jacks at the back of the amp. But during this particular performance I lent my leads to my guitarists, and simply plugged my bass straight into the Input jack in the front left hand corner of the amp.

I don't use any pre-amps, though my bass has an active pre-amp.
 
#8
BassmanPaul said:
What cabinets were you using with the amp at the time???

Did jumpering the send return jacks do anything??

Paul
Click to expand...

I was using my usual rig which consists of the G.K plugged into a 15'' Celestion loaded Laney cabnet worth NZ $600 which I usually use. Earlier in the day I plugged in a the Laney cab plus a 4x10 Peavey Cabinet.

I don't quiet get what you mean by jumpering? Usually just plug my effects unit from the Left and Right labled Output jacks on the Boss Effects Unit into the Send (Left) and Return (Right) jacks on the rear of the G.K 400 RB.

:bassist:
 
#9
WingKL said:
it's a bit hard to troubleshoot your amp over a forum.
Click to expand...

Au contraire mon ami!! All that needs to be done is fill out this little information form..........

Hi! I'm your friendly amp technician! I live perhaps thousands of miles outside the range of hearing and seeing your amp - even when it's turned up and working! So I've devised this handy questionnaire! In order to help me more efficiently diagnose and repair the problem with your amplifier please respond to the following points:


~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. Describe your problem:

2. Now, describe your problem accurately:

3. Speculate wildly based on faulty knowledge about almost everything
just what's the cause of your problem:

4. Please indicate the severity of your problem:
A. Minor___ B. Minor___ C. Minor___ D. Trivial___

5. Nature of problem:
A. Sounds bad___ B. Sounds really bad___ C. No sound___
D. Strange smell___ E. Smells really bad twice___

6. Was your amp plugged in?
Yes___ No___

7. Was it turned on?
Yes___ No___

8. Did you try to fix it yourself?
Yes___ No___

9. If so, did you make it worse?
Yes___ Yes___

10. Did you have a "friend" who "knows all about amps" try to fix it for you?
Yes___ No___

11. If so, did they make it worse?
Yes___

12. Have you read your manual?
No___ No___

13. Are you sure you've read the manual?
Maybe___ No___

14. Are you absolutely SURE you read the manual?
No___ I was going to...___

15. If you DID read the manual, do you think you UNDERSTOOD it?
Yes___ No___

16. If yes, explain why you can't fix the problem yourself:

17. What were you doing to your amplifier at the time the problem occurred?

18. If you answered "nothing", explain why you think there's a problem:

19. Are you sure you're not imagining the problem?
Yes___ No___

20. Does the clock on your DVD player always blink 12:00?
Yes___ That's a clock?___ What's a DVD?___

21. Do you have any electronic devices that DO work?
Yes___ No___

22. Do you have an independent witness to the problem?
(Does not include drummers)
Yes___ No___

23. Have you given the amplifier a good whack on top?
Yes___ No___

24. Did the amplifier catch fire?
Yes___ Not yet___

25. Do you have another amp you can use while you wait to take this one
to a repair shop like you should have done in the first place?
Yes___ No, I prefer to be out of commission longer___

26. Has the foam inside your speaker cabinet caught fire repeatedly?
Yes___ No___ What's a "cabinet"?___

27. Has the foam inside your speaker BOX caught fire repeatedly?
Yes___ No___

28. If so, did you replace it with an approved dampener?
No. Enough beer gets spilled in there to keep it safe___
No. The cat's always whizzing in there after a good scratch on the carpet anyway___
Yes___

28. Let me restate this: If so, did you replace it with an approved DAMPING material?
Yes___
No. My drummer used all the egg cartons inside his kick drum instead. ___

~~~~~~~~~~~~~~~~~~~~~~~~~~~
__________________
<-- greenboy ---<<<<
 
#10
:D Sorry, I just had to post that ...LOL!!

What he meant by jumpering is inserting a cord with plugs from the "effects send" to the "effects return", basically as a "jumper".
Sometimes those jacks develop an oxidization on the contact points from non-use. By patching a cable between them, you would be cleaning the contacts. Might work. Might not. Just a good first diagnosis step.

If you've been using something in the FX loop, it's probably not gonna help though.
 
#12
LTDVIPER333 said:
I was using my usual rig which consists of the G.K plugged into a 15'' Celestion loaded Laney cabnet worth NZ $600 which I usually use. Earlier in the day I plugged in a the Laney cab plus a 4x10 Peavey Cabinet.

:bassist:
Click to expand...

If using both cabinets brought your total load below 4&#937; then you could have blown your amps output stage. IIRC it's a 4&#937; minimum amp.

Paul
 
#13
lbwdog said:
Au contraire mon ami!! All that needs to be done is fill out this little information form..........

Hi! I'm your friendly amp technician! I live perhaps thousands of miles outside the range of hearing and seeing your amp - even when it's turned up and working! So I've devised this handy questionnaire! In order to help me more efficiently diagnose and repair the problem with your amplifier please respond to the following points:


~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. Describe your problem: Amp light showing its running power but absolutely no sound emitting from it

2. Now, describe your problem accurately: No sound emitting from amplifier apart from occasional crackling noises

3. Speculate wildly based on faulty knowledge about almost everything
just what's the cause of your problem: Blown fuse, Amp dead from age, power plug at the back of amp faulty, lose output and input jacks. Amp unable to handle being switched from multi-fx unit to having bass simply run into input jack. Amp unable to handle being plugged into more than one cabinet in practice before gig!

4. Please indicate the severity of your problem:
A. E. Serious!

5. Nature of problem:
C. No sound


6. Was your amp plugged in?
Yes

7. Was it turned on?
Yes

8. Did you try to fix it yourself?
No

9. If so, did you make it worse?

10. Did you have a "friend" who "knows all about amps" try to fix it for you?
No

11. If so, did they make it worse?


12. Have you read your manual?
Yes

13. Are you sure you've read the manuaL
YES

14. Are you absolutely SURE you read the manual?
YES

15. If you DID read the manual, do you think you UNDERSTOOD it?
Yes

16. If yes, explain why you can't fix the problem yourself: Because the particular manual I was given didn't have any pages on amp malfunctioning. Also amp simply wouldn't go and i established it wasn't the a,bass b. cable or c.cabinet, by plugging amp into independent bass cable and cabinet. Plus I'm useless with electronic devices!

17. What were you doing to your amplifier at the time the problem occurred? Playing a gig at a local pub, running the amp at low volume through a mic'd up Laney RB 1x15 8ohm cab that belongs to me.

18. If you answered "nothing", explain why you think there's a problem:

19. Are you sure you're not imagining the problem?
No

20. Does the clock on your DVD player always blink 12:00?
Yes

21. Do you have any electronic devices that DO work?
Yes

22. Do you have an independent witness to the problem?
(Does not include drummers)
Yes

23. Have you given the amplifier a good whack on top?
No

24. Did the amplifier catch fire?
Not yet

25. Do you have another amp you can use while you wait to take this one
to a repair shop like you should have done in the first place?
No, I have taken it to a repair shop!

26. Has the foam inside your speaker cabinet caught fire repeatedly?
No not at all
27. Has the foam inside your speaker BOX caught fire repeatedly?
No

28. If so, did you replace it with an approved dampener?
No. Enough beer gets spilled in there to keep it safe___
No. The cat's always whizzing in there after a good scratch on the carpet anyway___
Yes___

28. Let me restate this: If so, did you replace it with an approved DAMPING material?

No. My drummer used all the egg cartons inside his kick drum instead. ___

:mad:
~~~~~~~~~~~~~~~~~~~~~~~~~~~
__________________
:bassist: :bassist: :bassist: :ninja:
Click to expand...
 
#14
BassmanPaul said:
If using both cabinets brought your total load below 4&#937; then you could have blown your amps output stage. IIRC it's a 4&#937; minimum amp.

Paul
Click to expand...

I don't quite get what you mean by this symbol &#937; ?

If you mean Ohms the G.K 400 RB can run either one 4 ohm or two 8 ohm Cabinet's, though a single 8 ohm cabinet like my Laney RB 115 works fine without any hassle. The Peavy 4x10 stack I used during an earlier practice was also 8 ohms. I also had a go plugging my amp into a 15'' 8 ohm P.A speaker, running the two, during an earlier practice session.
 
#16
Just wanted to mention that the exact same thing happened to me at a gig last Friday; I use a very old 400RB that was bought secondhand. The first few songs went well, but the volume started to cut out about half way through our set. I had to go through the PA afterwards, which wasn't as terrible as I imagined it would be... I've since ordered a replacement.

I didn't think this amp would last too long, given its age and the fact that it was used. I still may get it fixed to keep as a backup though, since I really do like some of the sounds I can get from it.
 
#18
having had a 400rb ,I'm gonna guess a cracked circuit board or loose solder joint. As much of a tank as that amp is, there's a certain amount of wear and tear that takes place moving it as well as getting vibrated from sitting on your amp. Sad to say but the diagnosis that might help is the old tried and true "smack the amp with your hand while its plugged in" method. If you hear any static at all, you will know the problem. Finding where the problem is , thats another story. Hope that helps
 
#20
I had this happen to me. I took apart the amp and saw that two leads had come loose from the board. I soldered them back in and it fixed the problem. It took me longer to take the amp apart than it did for me to do the soldering. I hope this helps.
 

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