Triple Rec clean tone is very dirty and weak
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94Tremoverb
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Did it sound like that before you changed the power tubes? Sorry if that's a stupid question! But if it didn't, put the old power tubes back and see if it comes right again.
If it's not the new power tubes, it could certainly be a preamp tube. You can test the various positions by first switching the FX loop to Bypass - with the rotary switch on the back, not the footswitch - if that doesn't fix it, you know that the problem is most likely not V4 (which is only used when the loop is active), and you can use the V4 tube to check the other positions, one at a time.
If it's not the new power tubes, it could certainly be a preamp tube. You can test the various positions by first switching the FX loop to Bypass - with the rotary switch on the back, not the footswitch - if that doesn't fix it, you know that the problem is most likely not V4 (which is only used when the loop is active), and you can use the V4 tube to check the other positions, one at a time.
thanks for the response
well this is how things unfolded for me....i was at our weekly rehearsal and i noticed a crackling noise when i had my amp on and off standby ready to jam and you could hear terrible crackling..i looked into the electronics and noticed a burnt screen resistor for tube #6...i ordered all new power tubes and the new screen resistor...i cleaned all the tube sockets and check the ohms of the smaller resistors located beside the screen resistor...i fired it up and it has a very dirty clean tone and channels 2 and 3 are for sure not the rec it use to be...
well this is how things unfolded for me....i was at our weekly rehearsal and i noticed a crackling noise when i had my amp on and off standby ready to jam and you could hear terrible crackling..i looked into the electronics and noticed a burnt screen resistor for tube #6...i ordered all new power tubes and the new screen resistor...i cleaned all the tube sockets and check the ohms of the smaller resistors located beside the screen resistor...i fired it up and it has a very dirty clean tone and channels 2 and 3 are for sure not the rec it use to be...
94Tremoverb
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It sounds like a tube blew badly and you may have lost half the output section - this will give you a 'half-wave' output, which is quieter than normal and sounds distorted in a bad way. Here are some tests to do:
First set the amp to Spongy/Diode, which will keep the voltages down but not risk any damage to the rectifier tubes. Then remove all six power tubes, making a note of which went where. Now try them in the amp one at a time, in the socket that each came out of. In each case, test the amp - it should produce sound, which will be no good for playing but you actually only need to hear the typical background hiss when the amp is on to know it's working. If any tube/position does not make a sound, make a note of which. After you've done that, and if there are any dead tube/sockets, try one of the *good* tubes in the dead sockets. If they're still dead you know it's a problem with the sockets, not the tubes. If all the sockets work, the tubes you marked as not working are dead.
(Unfortunately, I'm expecting that up to three tube sockets may be dead, in the same half.)
If *all three* sockets on the same side are dead, it could be a blown phase inverter tube (V5). Try replacing it with either a spare 12AX7, or if you don't have one, temporarily pull the FX loop tube (V4) to use and bypass the loop.
If it's not that, it's some other fault causing half the output section to not work. The best case is a failed coupling cap or phase inverter plate resistor (or something very similar and related to it) and at worst it's the output transformer - if you're very unlucky, a blown tube can sometimes do this. If you're not familiar with troubleshooting and dangerous voltages, you may be best to leave it to a tech at this stage.
First set the amp to Spongy/Diode, which will keep the voltages down but not risk any damage to the rectifier tubes. Then remove all six power tubes, making a note of which went where. Now try them in the amp one at a time, in the socket that each came out of. In each case, test the amp - it should produce sound, which will be no good for playing but you actually only need to hear the typical background hiss when the amp is on to know it's working. If any tube/position does not make a sound, make a note of which. After you've done that, and if there are any dead tube/sockets, try one of the *good* tubes in the dead sockets. If they're still dead you know it's a problem with the sockets, not the tubes. If all the sockets work, the tubes you marked as not working are dead.
(Unfortunately, I'm expecting that up to three tube sockets may be dead, in the same half.)
If *all three* sockets on the same side are dead, it could be a blown phase inverter tube (V5). Try replacing it with either a spare 12AX7, or if you don't have one, temporarily pull the FX loop tube (V4) to use and bypass the loop.
If it's not that, it's some other fault causing half the output section to not work. The best case is a failed coupling cap or phase inverter plate resistor (or something very similar and related to it) and at worst it's the output transformer - if you're very unlucky, a blown tube can sometimes do this. If you're not familiar with troubleshooting and dangerous voltages, you may be best to leave it to a tech at this stage.
thanks for your help...after reading what you said about bypassing the fx loop...i tried that and that cleaned up everything completely...i have some spare mesa 12AX7A Russian 2's and tried them in V4, not able to get that great clean with the loop engaged
94Tremoverb
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That's great, I probably should have asked you to test that first before I wrote all that... 
If you need to use the loop or the Output and Solo controls, you will probably need to have it looked at. If a new tube doesn't cure it there's likely to be something wrong with the circuitry. Make sure you have the Send level set right though - not too high.
If you need to use the loop or the Output and Solo controls, you will probably need to have it looked at. If a new tube doesn't cure it there's likely to be something wrong with the circuitry. Make sure you have the Send level set right though - not too high.
....thought I had it fixed however problem still lurks....i just talk to a Mesa tech and he had said this is classic problem happening with the loop. He said to check the many FET J175's located around the circuit for failure..he said the middle leg should read about .5volts engaged...i am going to check this out this evening to see how many are leaking. he said this happens all the time and is the main thing he fixes on these amps...just wanted to give an update so other people could gain info to their issues if they are having them...
I am taking it to get repaired tomorrow and will post what he had to actually do...this may help someone else figure out their problem..
thanks again
bobby
I am taking it to get repaired tomorrow and will post what he had to actually do...this may help someone else figure out their problem..
thanks again
bobby
well I have my amp back from the repair shop...i had six bad FET J175' in the loop section..this took care of the crackle that I was hearing when my guitar was off standby and ready to jam...(the crackle sounded like a dirty knob when you turn it...real scratchy without touching anything) however my clean channel still sounds like crap when the loop is engaged..i have changed all preamp tubes, power tubes. seems to get worse the longer the amp is on..when I bypass the loop amp is 100%...anyone have any suggestions other than send it to Mesa?
