I have a buzz, in the background, a distorted sound. My GK 1001RB 2x10 combo will still reach full volume...but that annoying buzz. I have 1) disconnected the 10's and hooked up another cabinet. 2) Tried different cables. 3) Tried a different bass. 4) Tried both the main input and also the effect return as an input(bypassing the preamp) Still the same buzzz in the background.(pedals taken out of the loop) I'll bring it into the shop if I have to, but I keep thinking its something simple. If anybody can help, then Thanks!..
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Oh yeah.. I've plugged into different outlets. It's not a polarity hum or anything like that. A fuzzy, distortion in the background along with fully amplified notes.
Buzz or is it hum?
Buzz is like hum but has more of an "edge" to it.
bzzzzzzzzzzz or hmmmmmmmm?
Distortion is your audio sounding like your audio only raspy or ragged.
The bass notes come through solid, but there's that underlying distortion, very ragged.
If the underlying noise is there when not playing, that is not what we normally call distortion.
With the bass and cable unplugged from the amp.
You have an undesireable noise that didn't use to be there.
The choices are at this point:
1. Hum mmmmmmmmmm
2. Buzz zzzzzzzzzzzzzzzzzz
and third possibility for an amp without audio running through it is,
3. Hiss sssssssssssssssssss
Pick witch one of the three best describes what you hear.
Distortion is only a consideration when playing at this point in the diagnostics.
We'll leave that out for now.
OK, now we're gettin somewhere.
Full volume doesn't really sound like a bad output transistor. Though depending on the output configuration, it is possible to be down a a db or 2 of 3 of 4 due to a bad transistor and you might not notice a volume difference.
But this happened with a different cab? So that kind of rules out speakers.
It's clean, no buzz or hum with bass and cable disconnected. Pretty well eliminates power supply or ground problems.
Not the cable, not the bass.
Set all your EQ to flat/mid range.
Does it make the same noise at all levels on the amp?
Same with all levels/eg. Can I test output transistors with a multimeter?
Yeah... no... you want to test them under load to be sure. You might find a short or an open. But if you have a leaky junction, that might not be very conclusive with a VOM. You are talking analog scale meter and not a DVM?
DVM are't very good at sorting out junction conductivity. I prefer a real live meter movement for that stuff.
You really want to be testing voltage drops around the transistors. It's more likely a coupling cap in the audio chain might be leaky and lettin' in some DC and upsetting the op voltages.
Please do not try any of this unless you are well experienced in electronic repair.
It's just transistors but it can still be dangerous.
And taking stuff apart if you don't know your way around... well you know.
Non-tech amp repair stoner guy says...
"Hey man, I think I found the problem."
"Your output transistors were leaking all of this white stuff."
I cleaned it all off of the heat sinks and put in new transistors."
"Funny thing dude, it didn't fix the problem."
"And dude... you should just get a good amp, cause this quit working after all that trouble and expense."
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Yeah... no... you want to test them under load to be sure. You might find a short or an open. but if you have a leaky junction, that might not be very conclusive with a VOM. You are talking analog scale meter and not a DVM?
DVM are't very good at sorting out junction conductivity. I prefer a real live meter movement for that stuff.
You really want to be testing voltage drops around the transistors. It's more likely a coupling cap in the audio chain might be leaky and lettin' in some DC and upsetting the op voltages.
Please do not try any of this unless you are well experienced in electronic repair.
It's just transistors but it can still be dangerous.
And taking stuff apart if you don't know your way around... well you know.
Non-tech amp repair stoner guy says...
"Hey man, I think I found the problem."
"Your output transistors were leaking all of this white stuff."
I cleaned it all off of the heat sinks and put in new transistors."
"Funny thing dude, it didn't fix the problem."
"And dude... you should just get a good amp, cause this quit working after all that trouble and expense."
Thank you! ..I'll bring it to the repair shop. Thanks for your help.. I'll have some insight to give them.. a thread to follow...
Hello Everyone. I was reading everyone's post to get answer with the issue on my MB210 1st gen combo. Lately, for some reason, the loudness was gone. Sound quality is still there and no farting sound, but even I'm at almost full volume and gain with the amp and almost full on my Bass, the sounds seems like its from a 10 watts.
If any of you encountered or experienced my issue, any advice for me to fix it will be greatly appreciated.
Many thanks.
xrz1616
If any of you encountered or experienced my issue, any advice for me to fix it will be greatly appreciated.
Many thanks.
xrz1616
Thanks for the advice.
I will try this process and see if it works.
Again, thank you much
xrz1616
Did you find a fix? Sounds like I have a similar problem on my 1001RB. Fine until it warms up then distortion on my signal but quiet otherwise.
Its really a guessing game on the internet.
The amp would need to be diagnosed with test equipment.
If it changes thermally it could be anything from bad connections that change from temperature.
like ribbon cables or solder connections. Or a actual faulty component like a semiconductor.
Anything from output devices or thermal tracking for bias.
Its basically a wild goose chase on the internet without measuring DC offset or seeing things on a scope.
The amp would need to be diagnosed with test equipment.
If it changes thermally it could be anything from bad connections that change from temperature.
like ribbon cables or solder connections. Or a actual faulty component like a semiconductor.
Anything from output devices or thermal tracking for bias.
Its basically a wild goose chase on the internet without measuring DC offset or seeing things on a scope.
