My Mesa blew up my EQ?

Discussion in 'The Workbench' started by Deftone, Sep 25, 2021.

  1. Deftone

    Deftone Well-Known Member

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    I just scored a Mesa Single Rec Solo 50 head. Sounds amazing, super stoked on it.

    So I set up my pedal board as usual, EFX send > MXR 10 band eq > Guyatone DD3 delay > BBE Sonic Maximiser > return. Everything sounds good except the MXR makes a loud pop when I click it on. Sounds like shit so I click it off. Another loud pop. I try it again, same thing. Amp seems fine when I play it with no efx.

    So I run my efx board through another amp. Now the MXR volume and gain lights are blinking, and when I click it on (no loud pop) there's almost no sound out of the amp. Turn it off (No loud pop) and the amp sounds fine again.

    Anyone have any idea WTF happened? I'm fucking bummed, I love that EQ.
     
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  2. ricksdisconnected

    ricksdisconnected Well-Known Member

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    i cant imagine the 2 are related
     
  3. TheToneDig

    TheToneDig Well-Known Member

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    Make sure you are using 18v to power the MXR. While I have not used the split cable method on that pedal I have on others. 2 x 9v outlets going to one 18v in on the pedal. Sometimes people get away with using 9v on 12-18v pedals without knowing it and then suddenly a problem appears.

    Your pedalboard stuff can't damage your amp and the amp can't really damage your pedalboard stuff. It is just a weak electromagnetic signal between the two down the guitar cable. The culprit is more than likely the powering of the pedal or the pedal has failed. Aren't flashing lights supposed to mean your gain and volume is too high on the pedal?

    Check the power and the 18v connection again maybe?

    You might need one of these. 18v split cable, 18v Y-cable, 9v doubler. They have a few names and come with different connections so make sure you get the one with the right connections for your power supply and pedal.

    [​IMG]
     
    Last edited: Sep 26, 2021
  4. PelliX

    PelliX Well-Known Member

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    Is the FX loop on the Mesa line level, and does the MXR accept that if so?
     
  5. Deftone

    Deftone Well-Known Member

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    Using 18v and have been for years. Lights just blink constantly now.

    Not sure about this. There is an adjustment knob for the FX Loop, it was set at 50%.

    Back panel.JPG
     
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  6. PelliX

    PelliX Well-Known Member

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    Seems to be line level from what I gather from the manual, the MXR is clearly intended for instrument level input. Assuming that all 'simple faults' like cables, knobs, etc have been ruled out, you're either dealing with a damaged input on the MXR or its power supply has gone south as @TheToneDig sort of suggested. Check the output voltage of the supply to rule that out. Assuming that's fine, why not post a gut shot of the MXR, I honestly have no idea what they look like inside. :)
     
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  7. ricksdisconnected

    ricksdisconnected Well-Known Member

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    hell try it on a different amp.
     
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  8. PelliX

    PelliX Well-Known Member

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    I think he did;

    Also, after googling a little, it looks like the MXR might be fully SMD inside - not the most fun to fix, in my opinion. That is, if it is broken...
     
    Last edited: Sep 26, 2021
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  9. tmingle

    tmingle Well-Known Member

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    Your 18V supply may have taken a dive. The wall warts are not always that great.
    Also, the FX mix on the Mesa suggests that it may be a parallel FX loop.
     
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  10. Deftone

    Deftone Well-Known Member

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    It's a Voodoo Lab Pedal Power 2+
     
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  11. Old Punker

    Old Punker Well-Known Member

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    Hi @Deftone I've got the same Mesa head, mine's Series 2 as well. If your amp hasn't been modded, then that is definitely a parallel FX loop you have. You probably want to check the manual closely for that section...that Mix knob is usually kept pretty low. I keep mine around 15% - 35%. If memory serves me correctly, you're supposed to keep the blend knobs on your time based effects cranked. If you have multiple time based effects in series it gets more complicated and there are websites that deal with dialing in parallel loops. I've read that these heads were designed to work with rack gear so regular pedals don't always work as expected. It took me a while to get used to dealing with the FX loop but I've kind of adapted to it.

    Hey what kind of cab/speakers are you using with it? I've been looking into getting the Mesa 2x12 Recto horizontal cab. Right now I have two 1x12's hooked up, one is closed back (ported) and the other is 1/2 open.
     
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  12. TheToneDig

    TheToneDig Well-Known Member

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    I found using a Y-splitter on that exact same power supply was the way to power my 18v stuff, not the other 12v outlets. Are you doing this with it? See the splitter next to the plectrum? (ignore the third 9v above the splitter. It is was just for another pedal outside of the image). All I can think of if that isn't it is your MXR EQ has seen better days.

    2x8vDiezel.jpg
     
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  13. PelliX

    PelliX Well-Known Member

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    The very best equipment fails eventually, you know. No harm in running a multimeter over the output. If that's it - easy fix.
     
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  14. Deftone

    Deftone Well-Known Member

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    Thanks for all the responses, very much appreciated. Unbelievably helpful group.

    Checked the power supply and it seems working fine, I'm searching for an 18v wall wart to double check the MXR but I think its toast. I was using a 4 way splitter with the Voodoo. One end was not connected. I checked with a multi meter and was getting 9.3 Volts output. (if I was doing it correctly) Set the multi meter at 20v DCV, red sensor inside the tip, black sensor on the outside? My pop was an Electrical Engineer, missing his advice right now.

    I don't know what a parallel loop is, so that's one issue. I'll research today. (should be fun side project to keep me amused at work)

    @Old Punker The head came with the Halfback 4x12. I always wanted this rig so when I saw them together for a reasonable price I decided to jump on it. Here's the thread: https://www.marshallforum.com/threads/jcm900-4500-or-mesa-solo-rectifier.122793/

    20210925_074728a.jpg
     
    Last edited: Sep 27, 2021
  15. PelliX

    PelliX Well-Known Member

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    Yes, some of the folks here are great!

    Well, using the Y-cable setup you should see ~18 - 20V-ish, single lead should be 9-10V-ish (voltage is often a little higher without a load). Positive and negative (red and black) don't matter here on a digital multimeter - if you do it the wrong way around you get the right number, just negative. No worries.

    Well, it 'mixes' the wet signal (FX you have in the loop) with the dry (original) signal. In series you only get the wet signal returned. In parallel the dry and the wet both reach the output stage. Very simply put.
     
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  16. Deftone

    Deftone Well-Known Member

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    Wow, you guys are making this interesting and fun.

    So maybe that was my issue, as @TheToneDig stated: insufficient voltage to the MXR. I thought the 4 way set up worked as it seemed to worked ok on my other (Phaez) amps. It was acting weird with the 2205 though. I was seeing the flashing (overloaded) lights occasionally with that amp as well.

    BTW, yes digital multimeter and I was seeing a neg. number.
     
  17. Deftone

    Deftone Well-Known Member

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  18. PelliX

    PelliX Well-Known Member

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    Most power supplies have the center pin as positive, it's pretty much the industry standard for DC barrel jacks. Guitar pedals and such are an exception to that rule, so your red probe (positive) would go on the outside. Still, as you noticed - the reading is valid, just inverted. Digital multimeters are forgiving in that respect... :)

    However, try the MXR on 18V and let us know how it went.
     
  19. Deftone

    Deftone Well-Known Member

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    Could not find my 18v power supply so I had to order a new "Y" cable and it finally arrived. Plugged it into my VL PP2 and measured voltage and it's putting out +18v. Plugged it into my MXR 10 and nothing. No lights, nothing. So I plugged a 9v lead into the MXR and it lights up again. Blinking lights. I guess it's toast.
     
  20. PelliX

    PelliX Well-Known Member

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    So the MXR 'fires up' on 9V but stays dead on 18V? That's odd. Sure you got the polarity right on the 18V? Again, gutshots might provide a clue as to what you're dealing with inside.
     
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