# Help with bass amp assessment



## Jeffery Young (Mar 5, 2019)

Gallien-Krueger MB150S-III for sale - "has a hum"





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I'm interested in this amp but have no knowledge on amp repair/assessment. Good price, but seller says it has "developed a hum and may need repair."

Any thoughts on potential issues and likelihood/cost of repair would be helpful. Is this a potentially good deal, or a hard pass?

Thanks,
Jeffery


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## Paul Running (Apr 12, 2020)

His description of the symptoms is rather vague. Hum problems are mainly improper grounding and or power supply filtering issues. Depending on your knowledge and abilities, it could be an inexpensive fix...we can help you. Try to obtain some greater detail of the hum. There is a service manual for this model, here it is:


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## Jeffery Young (Mar 5, 2019)

Paul Running said:


> His description of the symptoms is rather vague. Hum problems are mainly improper grounding and or power supply filtering issues. Depending on your knowledge and abilities, it could be an inexpensive fix...we can help you. Try to obtain some greater detail of the hum. There is a service manual for this model, here it is:


Thank you Paul. Any recommended questions I could send the buyer to better diagnose the potential issue? I have a sense that they are mostly interested in offloading the amp without much fuss, so I doubt I could get them to do anything too elaborate.


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## sulphur (Jun 2, 2011)

Jeffery Young said:


> Thank you Paul. Any recommended questions I could send the buyer to better diagnose the potential issue? I have a sense that they are mostly interested in offloading the amp without much fuss, so I doubt I could get them to do anything too elaborate.


I didn't notice a price in the ad. 

I have one of these amps and it's a great little grab and go, sounds quite good.
I've brought it to some jams with buddies and they were quite impressed.

I don't have a ton of hours on mine, but haven't had any issues.
It may be the wiring in the guys house for all we know. Sorry I'm not much help.


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## Jeffery Young (Mar 5, 2019)

sulphur said:


> I didn't notice a price in the ad.
> 
> I have one of these amps and it's a great little grab and go, sounds quite good.
> I've brought it to some jams with buddies and they were quite impressed.
> ...


It's posted for $100.

Yeah, I've rented one of these before and really liked it. Other forums seem to suggest these are getting a bit "outdated" but there's something about the tone that I enjoyed over some other modern options.

And yes, I hear you on the possibility that it could just be the house/guitar wiring causing the hum - I hope so!


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## Paul Running (Apr 12, 2020)

Jeffery Young said:


> Any recommended questions I could send the buyer to better diagnose the potential issue?


It would help to know if it was a sudden change from quiet noise to the hum problem. Is there certain conditions that the hum subsides or gets louder...was it ever quiet. Does the hum change when plugged into another receptacle. Questions that may isolate to an actual equipment issue...if may be a simple fault to rectify.


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## sulphur (Jun 2, 2011)

Jeffery Young said:


> It's posted for $100.
> 
> Yeah, I've rented one of these before and really liked it. Other forums seem to suggest these are getting a bit "outdated" but there's something about the tone that I enjoyed over some other modern options.
> 
> And yes, I hear you on the possibility that it could just be the house/guitar wiring causing the hum - I hope so!


$100 is a bargain and maybe worth the chance even if it needed repair.
I think that I paid around a grand new for mine.


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## Latole (Aug 11, 2020)

If you know a good and honest amp tech go ahead. Otherwise, don't buy it


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## nonreverb (Sep 19, 2006)

They're decent amps. I got a GK RB400 for $60 a few years ago that had power supply issues. I had it fixed in under half an hour. The issues don't sound too serious on this one.


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## Latole (Aug 11, 2020)

nonreverb said:


> They're decent amps. I got a GK RB400 for $60 a few years ago that had power supply issues. I had it fixed in under half an hour. The issues don't sound too serious on this one.


 Is the OP have your skill in electronics ? 
You can't tell about the issue until it is fix . It may cost few hours for tech .

It is like to play lotto.


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## nonreverb (Sep 19, 2006)

Latole said:


> Is the OP have your skill in electronics ?
> You can't tell about the issue until it is fix . It may cost few hours for tech .
> 
> It is like to play lotto.


It sounds like a fairly simple issue. I'd be confident that it could be repaired within an hour based on the problem description and the fact the amp seems to be fully operational otherwise. Anyone who's charging a "few hours" for a symptom like that on one of these amps, needs a new occupation. IMO


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## Latole (Aug 11, 2020)

nonreverb said:


> Anyone who's charging a "few hours" for a symptom like that, needs a new occupation. IMO


Will you refund OP if he pay too much ? 
Link for this tech ?


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## nonreverb (Sep 19, 2006)

Latole said:


> Will you refund OP if he pay too much ?
> Link for this tech ?


Dude....It's $100 to start with. Putting a $100 more into it is nothing. That said, if I estimated an hour's labour and it went over, I would always honor the hour. Having worked on several of these, I'd be confident in my estimate.
This begs the question of intent though. If a tech is out just to make as much money off the customer as they can, they'll gouge them for a simple problem. Conversely, if the tech is not experienced or dare I say, incompetent then yes a few hours might be required.


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## nonreverb (Sep 19, 2006)

Latole said:


> Will you refund OP if he pay too much ?
> Link for this tech ?


I should probably clarify this by stating that the estimate would be based on the hum only!
I would want to ascertain that there are no other issues besides the hum before committing to an estimate.
That's where things can get expensive depending on what the issues are.


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## Latole (Aug 11, 2020)

It is possible that you are right, but as it is not my money I prefer to consider the worst.


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