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Discussion Starter · #1 ·
Hey I got a couple questions about the mesa 50cal plus only had for since friday. When I dont have the lead pot pulled ( so on clean channel), there is alot of hum when the strings are muted or guitar volume turned off ; so whenever no notes are coming through speaker/not playing<<even at indoor playing volume.

Then when i pull the lead pot (go to channel 2) it goes dead silent lol. The hum is gone, and it all is normal sounding. Not a huge problem but im assuming the hum isnt normal.

Second issue and more scary issue. I understand the way that Mesa/Boogie made the controls to work together (ex. Treble set first; and it affects the mids and bass, and how the volumes must be set in correct ratio when going up in volume and they taper different) and have gotten solid feel for how that goes.
So that being said, here is the issue. There is sometimes a high pitch squealing sound that comes out when i use higher gain or volume or presence settings. Its not always there and comes at weird times with no pattern except the one above. It sometimes goes away for a few seconds if i jiggle one of the pots a little bit or if i play with it squealing for awhile it will go away. if i turn down the volume on the guitar while its happening the pitch of the squeal will actually get higher. Its limiting my possible tone improvement cuz i have to leave the controls in the max spots i can before the squealing starts. Sometimes it comes in loud, sometimes not that bad but there. I've been constantly trying new settings to get familiar with the amp so that why its sometimes never the same.
This problem is on both channels, and it isn't affected if the strings are muted and volume is on ; its not feedback or normal (or my guitar).

Also is the preamp/power amp housing sitting on springs lol. it jiggles a little when i move the amp and sounds like its sitting on little springs (to act like mini shocks possibly?)

Any Ideas? (possibly tubes?) I will call Mesa monday when they r open to get advice but would like to have some idea of what the problem is.
Thanks for reading all that crap lol!!!

Quotes from manual:
"And in order to do this its controls must be very powerful. When turning up the
Master and/or Lead Master and playing quite loudly, you should expect to reduce the Volume and
possibly the Treble and/or Presence"

"
But you cannot run both the Volume and the Masters wide open at the same time
without encountering feedback. There will always be an optimal point between the two controls that
balances preamp gain (Volume) against power amp loudness (via the Masters)"

"
MAINTENANCE Excessive noise, feedback, squealing or rattling sounds coming from the speaker
are almost always the result of a deteriorated 12AX7 preamp tube, usually the first ("V1") or the
second ("V2") tube on the right (as seen from the rear), nearest the input jack. Checking the preamp
tubes in a tube tester is almost useless. The best procedure is to substitute a tube that's known to be
good and noise-free in each possible tube location, one at a time. Here are some clues to speed up
the process: if the problem appears only in the Lead mode, then the culprit is probably V1, V2, or V3.
(V1 is the tube nearest the input jack; V2 is the "next one out"; etc.) If the problem is in the Rhythm
mode only, then V2 is usually the problem. If the reverb is noisy or has some other problem, replace
V4. (Unlike the other preamp stages, V4 requires a 12AT7-type tube.)
Sometimes the insides of the power tubes themselves can be heard rattling. If the power is weak and
your tone is flat, try replacing the larger power tubes, type 6L6GC. "
 

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Discussion Starter · #2 ·
bumpzor

I got to turn it up to about 7 on master today and it was fantastic reguarding the squealing... didnt have any at all... only at low volume. also switched the 6L6's spots (just different places not new tubes) didnt seem to help lol
 

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you have a bad tube. I would go with eurotubes. get a whole set of new tubes. Be sure to get the "high gain" set of output tubes. these give you more headroom on the dirty channel.

The reason channel one has hum is because of a bad preamp tube.

PS, if you have new tubes, then get some contact cleaner from radioshack. spray some on the tubes and push them in and out of the socket a few times. allow the tubes to dry adequately. then replace.
 

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Discussion Starter · #4 ·
thanks speedy appreciate it!

Think I need to replace all of the preamp tubes and both power ones?

Its my first tube amp ive actually owned so new to them other than the basics of
"how to not kill your amp" lol

Genius idea about contact cleaner. That should really clean her up and get rid of corrosion building since the 80s hah. Better conductivity
 

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Discussion Starter · #9 ·
yeah i will change all the tubes eventually for sure. But i have limited money at the moment lol and would like to just change whatever is causing the issues at the moment lol. (all preamp or all poweramp tubes whichever would be the culprit) THANKS
 
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