| Author |
Message |
    
Anonymous
| | Posted on Wednesday, October 02, 2002 - 04:58 pm: | |
Langley or any of you other helpful knowledgeable guys. My MM210-135 has what sounds like a slight hum mixed with hiss sound. Switching the ground switch has no effect, my buddy looked at the tubes and showed me one (of the large ones) has a blue glow, he says indicates "bad". What do you think?
We did tweak knobs to get a great "overdrive" slight fuzz effect with master at 5 and volume at 10-so still can play it OK-but would like to cure the hum/hiss.
Thanks,
Cannonball
p.s. I was the guy with the "low volume is a bad tube?" thread last summer. |
langley
| | Posted on Thursday, October 03, 2002 - 04:16 pm: | |
`Ola, Ann Nonomous!
Re. the 'blue tube glow', it's 'Red Plate Glow' that's really bad. A little blue glow ought to be visible in all the tubes. It's just a reaction of the tubes internal substrates to all those happy and focused electron emitions.
How 'used are the tubes?
Buy a matched set set of tubes. If they're beat you're gonna have to change them anyway. Don't forget to 'bias'. (BTW, if you get Groove tubes,
their strength numbering systems don't mean diddly in an amp with non-cathode biasing -
that is, once an amp is biased properly (non cathode) a GT strength 2 tube will sound just like a GT strength 9 tube.)
As far as the hum/hiss goes, does it occur on both channels? if it does, try a different cable. If it still happens with a new cable (just a cable, no stomp boxes or wireless stuff). Else try a different guitar - one that's well shielded
and gas good humbuckers - like a real Les Paul.
Maybe the input jacks are worn and/or dirty.
Try both channels low-gain input # 2.
Does it still hum/hiss? (Do you gig in or near nuclear facilities?)
Does the 'slight hum/hiss' occur when nothing is plugged into the amp,and all controls are zero?
If so, it's probably the start of 'cap time'.
I get the feeling that there's an impediment
in the signal path, since the amp is still working
and sounds good cranked. Something non-exotic.
Sounds like it just needs a little TLC - but hey,
'ya never know.
I hope that this non-technical 'common sense' approach helps you a out, some.
Any amp which doesn't respond to user-type repairs
is an excellent candidate for a pro's bench.
He's got a singal injector, an oscilloscope,
and hopefully the correct schematic.
(Chicks Love the Signal Injector, and you can
fool em into believeing that the oscilloscope
is a sonogram machine. Boy, you can have fun with that!)
Good Luck.
PS> Tube amps have internal voltags that are present even when the amp is OFF. This is dangerous. It can Kill, Throw you across a room
(happened to me), and do things to parts of your body that no hot or even marginal chick will ever tolerate (unless you got lots of cash).
SO STAY OUT OF THE AMP'S INNARDS. Please?
SEE A TECH!! |
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