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BucketBucket Frets: 7751
I just plugged into my Mesa and it isn't working.

It turns on fine, and the lights come on but when I plugged the guitar cable in, which runs to my pedalboard, it seemed like there was a bit of an electrical issue - it sounded like it was crackling like a static shock, and the red light for the overdrive channel flickered on and off quickly as this shock noise happened. Once plugged in and off standby, no sound. An occasional pop or crackle when hitting the strings very hard, but nothing else.

It's plugged into the usual speaker cab and nothing has changed on it since I last plugged it in, and it worked perfectly.

What the fuck is going on?
- "I'm going to write a very stiff letter. A VERY stiff letter. On cardboard."
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  • BucketBucket Frets: 7751
    Also - once I unplugged the lead I got a bunch of hum that sounded like the noise from holding a cable against the input of a guitar.
    - "I'm going to write a very stiff letter. A VERY stiff letter. On cardboard."
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  • ICBMICBM Frets: 71959
    How comfortable are you about opening it up yourself?

    The flickering channel light being part of the problem suggests it's not valve-related, so there's little or no point in replacing any of those.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • BucketBucket Frets: 7751
    ICBM said:
    How comfortable are you about opening it up yourself?
    Not even slightly.

    What would you suggest needs doing?
    - "I'm going to write a very stiff letter. A VERY stiff letter. On cardboard."
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  • Drew_TNBDDrew_TNBD Frets: 22445
    Plug into the FX loop return and see if you get sound.
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  • BucketBucket Frets: 7751
    Plugged into the front but unplugged the cable for the footswitch this time - the red overdrive channel light came on but still no sound. Got a pop noise from unplugging the cable from the input, even on standby.

    Then plugged into the FX return. I got a clean sound but it was significantly more muffled and less trebly than it should have been, and the channel switch on the front didn't work. Again, got a pop from unplugging. When I plugged the footswitch cable back in, that didn't work either.
    - "I'm going to write a very stiff letter. A VERY stiff letter. On cardboard."
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  • Drew_TNBDDrew_TNBD Frets: 22445
    Okay, so that implies the power section is working fine. The tonal character is fine, when you're plugged directly into the FX loop you're not going through any preamp shaping, so what you're hearing is your RAW guitar through the poweramp and speaker.

    When you say the channel switch wasn't working, what do you mean exactly? The lights didn't switch or just that the sound didn't change? Plugged into the FX return, you shouldn't expect the distortion to change or anything. 
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  • BucketBucket Frets: 7751
    The sound didn't change, but the light did switch. When I plugged the footswitch back in, that did nothing at all.

    May be a bizarre question but I'm going to fire away anyway.

    I hired out my other amp - a 68RI Deluxe Reverb - to a mate this weekend for recording. During the load-in, it fell off a trolley and sustained some damage. As far as I can tell, it's only cosmetic. Some of the knobs are chipped and one of the pots is a bit stiffer than it used to be - slightly bent, I assume. I plugged it in and it still works fine and sounds wonderful, but is there any chance this accident has left it with some unseen gremlin in the circuit that has maybe knocked the Mesa somehow? The DRRI was on standby when I turned the Mark Five on. I'm wondering if there's some kind of change in the current draw or voltage or something that caused it to freak out.

    It sounds like the stupidest question in the world, but I only ask because the two amps were on at the same time, and the Mesa had no issues at all when I last played it, a couple of days ago.
    - "I'm going to write a very stiff letter. A VERY stiff letter. On cardboard."
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  • ICBMICBM Frets: 71959
    No, it's impossible that it's anything to do with the Fender.

    My guess based on experience of recent Mesas would be that one of the PCB jumper connectors is making a poor contact - however I wouldn't know which in a Mark V, since I've not been inside one of those yet. If you're not comfortable opening it up to check I would suggest taking it to a tech - it could also be something else, but whatever it is it's just an unfortunate coincidence.

    I hope your mate is going to pay for your Fender to be looked at too - it probably should be even if you can't find any serious damage. At best it will probably need a new pot.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • BucketBucket Frets: 7751
    ICBM said:
    I hope your mate is going to pay for your Fender to be looked at too - it probably should be even if you can't find any serious damage. At best it will probably need a new pot.
    Yes, he offered. And while I don't mind the "relic" look, I do want it to be fully functional.
    - "I'm going to write a very stiff letter. A VERY stiff letter. On cardboard."
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  • Drew_TNBDDrew_TNBD Frets: 22445
    Bucket said:
    The sound didn't change, but the light did switch. When I plugged the footswitch back in, that did nothing at all.
    Okay, so when you go into the FX return you're not going to hear the sound change when you switch channels. Coz you're skipping all the electronics that are part of the channels and just going straight into the power amp. My money is on a dicky preamp tube. Do you have any 12AX7's knocking around??
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  • BucketBucket Frets: 7751
    Drew_TNBD said:
    Bucket said:
    The sound didn't change, but the light did switch. When I plugged the footswitch back in, that did nothing at all.
    Okay, so when you go into the FX return you're not going to hear the sound change when you switch channels. Coz you're skipping all the electronics that are part of the channels and just going straight into the power amp. My money is on a dicky preamp tube. Do you have any 12AX7's knocking around??
    That makes sense.

    I don't, which is a bugger. I think I'm going to need to get it looked at - it could be a valve, but I want to make sure it's not something more sinister. Wouldn't I have seen/heard some warning signs if a valve was starting to go?
    - "I'm going to write a very stiff letter. A VERY stiff letter. On cardboard."
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  • Drew_TNBDDrew_TNBD Frets: 22445
    If you wanna bring it round mine and I'll take a look I'd be more than happy to. I'm no expert, but if it's just a preamp valve I can get you up and running quickly.
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  • BucketBucket Frets: 7751
    Drew_TNBD said:
    If you wanna bring it round mine and I'll take a look I'd be more than happy to. I'm no expert, but if it's just a preamp valve I can get you up and running quickly.
    Can I get back to you about that? I may have some help with it already from a friend of a friend but if not, it'd be appreciated!
    - "I'm going to write a very stiff letter. A VERY stiff letter. On cardboard."
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  • Drew_TNBDDrew_TNBD Frets: 22445
    Sure man!
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  • olafgartenolafgarten Frets: 1648
    Wow I just looked at the tube complement of the Mark V, it has 7 12AX7s! Finding the broken one will be fun! 
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  • BucketBucket Frets: 7751
    So I just took it round to a mate of my dad's, who knows a lot about amps. He planned to plug in the preamp stage into a different power amp (an Egnater Tweaker head) and vice versa, and see where the issue was.

    But first I plugged it in as normal - into an 8 ohm speaker cab, with the footswitch plugged in... flicked it off standby... and the fucking thing worked perfectly.

    We went through everything anyway, the whole process, testing the pre and power stages separately, then checking the footswitch was working, then the effects loop, etc etc etc, and everything was completely as it should have been, with no suggestion of anything being wrong.

    Utterly fucking bizarre.
    - "I'm going to write a very stiff letter. A VERY stiff letter. On cardboard."
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  • ICBMICBM Frets: 71959
    I still think that sounds like a loose PCB connector - which got disturbed and accidentally fixed by moving the amp. @BintyTwanger just had a similar fault with a Rectoverb that worked perfectly after going back to the shop. I've had similar not-showing-up-when-it-gets-to-the-shop faults with them too.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • BucketBucket Frets: 7751
    Plugged back in today - no issues, turned on fine and makes sound, but for whatever reason it now hums pretty loudly, when it didn't before. It's not audible when playing, but it's pretty loud when I'm not. It's quiet but audible on the clean channel, and louder on the dirty channel - I was using a guitar with humbuckers, and the volume of the hum was similar to a P-90. This happens regardless of the volume setting on the guitar, so I know it's the amp, and nothing else in my setup has changed.
    - "I'm going to write a very stiff letter. A VERY stiff letter. On cardboard."
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  • ICBMICBM Frets: 71959
    Is it affected by the reverb level?

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

    0reaction image LOL 0reaction image Wow! 0reaction image Wisdom
  • BucketBucket Frets: 7751
    I'll check tomorrow!
    - "I'm going to write a very stiff letter. A VERY stiff letter. On cardboard."
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