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Author Topic: Mesa 50/50 lo power issue  (Read 1376 times)

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Soloist

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Mesa 50/50 lo power issue
« on: Time Format »

Hey all,
since I re-configured my rig I thought I would give the 50/50 another shot. First off it sounds great, way better than before. I simplified my rack a bit so the gain staging is much easier. The issue I am having is on lo power it sounds like a blown speaker on one side. I swapped the speakers leads and it moved to the other cab. Ok the speaker isn't the issue. It doesn't do it on hi power, so what do I need to do to fix the lo power setting?
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Live Rig:
Preamps -ADA MP1-ADA MP2-Marshall JMP1-Digitech GSP1101
Post Effects -TC Electronic G Major2-TC Electronics G Force-BBE 482i
Pre Effects -Boss NS 2-Boss GE 7-Radial Engineering Hot British-Ibanez TS9-MXR M108-Boss SD1
Mixing/Switching -Alesis Multimix8-Voodoo Lab GCP-Voodoo Lab Amp Selector- Radial Engineering Big Shot I/O v2
Power - ADA MT200-Mesa 50/50-Voodoo Lab ISO5 Pedal Power-Furman RP8-Livewire PC1100
Axes - Charvel So Cal Pro Mod-Jackson DK2MQ Pro-Jackson USA Soloist-Ibanez RG3XXV
Cabs -4 2x12 ADA Split Stacks

Systematic Chaos

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Re: Mesa 50/50 lo power issue
« Reply #1 on: Time Format »

I’ll send you the orig Boogie service schematics when I get home. I had the same issue with my old 50/50 in 2009 and the culprit was a faulty resistor in the fixed bias circuit.

*edit* here’s the doc: https://www.dropbox.com/s/tieq9t4izk4dz3c/5050%2BMod.pdf?dl=0
« Last Edit: Time Format by Systematic Chaos »
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Mesa Boogie MkIVb short head, ADA MP-1 v2, Fractal AxeFX II, Rocktron Velocity 150; Digitech GSP1101, DigiTech 2120Artist, Carvin Tube 100, Yamaha MFC10//
Ibanez RG550RF, Ibanez 540S-LPF DY, Ibanez RGR620TKS, Ibanez RGR620TPS, Ibanez RG550Ltd BK, Ibanez RG7620MSOL, Ibanez RGR465MCA, Ibanez RGR765RCB, Ibanez RG620QMSP, Ibanez RG1420FBHB, Ibanez RGT42MDX, 90s ESP M-II Dlx //
DiMarzio CrunchLab/ToneZone/Gravity Storm/Liquifire/AirNorton/PAF Pro/HfH/ibzUSA F Series pups

Soloist

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Re: Mesa 50/50 lo power issue
« Reply #2 on: Time Format »

Thanks SC!  I figured you or MJMP would know. Had a feeling it was a resistor I just didn't know where. :bow:
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Live Rig:
Preamps -ADA MP1-ADA MP2-Marshall JMP1-Digitech GSP1101
Post Effects -TC Electronic G Major2-TC Electronics G Force-BBE 482i
Pre Effects -Boss NS 2-Boss GE 7-Radial Engineering Hot British-Ibanez TS9-MXR M108-Boss SD1
Mixing/Switching -Alesis Multimix8-Voodoo Lab GCP-Voodoo Lab Amp Selector- Radial Engineering Big Shot I/O v2
Power - ADA MT200-Mesa 50/50-Voodoo Lab ISO5 Pedal Power-Furman RP8-Livewire PC1100
Axes - Charvel So Cal Pro Mod-Jackson DK2MQ Pro-Jackson USA Soloist-Ibanez RG3XXV
Cabs -4 2x12 ADA Split Stacks

Soloist

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Re: Mesa 50/50 lo power issue
« Reply #3 on: Time Format »

Ok SC, after looking over the schematic I see 4 resistors in the fixed bias circuit.
R322
R201 10k
R241 47k
R242 68k
Any idea which one I need to replace? I was hoping that you remembered which you replaced.
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Live Rig:
Preamps -ADA MP1-ADA MP2-Marshall JMP1-Digitech GSP1101
Post Effects -TC Electronic G Major2-TC Electronics G Force-BBE 482i
Pre Effects -Boss NS 2-Boss GE 7-Radial Engineering Hot British-Ibanez TS9-MXR M108-Boss SD1
Mixing/Switching -Alesis Multimix8-Voodoo Lab GCP-Voodoo Lab Amp Selector- Radial Engineering Big Shot I/O v2
Power - ADA MT200-Mesa 50/50-Voodoo Lab ISO5 Pedal Power-Furman RP8-Livewire PC1100
Axes - Charvel So Cal Pro Mod-Jackson DK2MQ Pro-Jackson USA Soloist-Ibanez RG3XXV
Cabs -4 2x12 ADA Split Stacks

Systematic Chaos

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Re: Mesa 50/50 lo power issue
« Reply #4 on: Time Format »

IIRC it was R242 on mine. If I were you I take a MultiMeter and measure them all. Also measure R229 (220k, parallel to the Hi/Lo Pwr Switch).
Since I had my PCB out back then I ended up replacing all component with new and higher qual/spec ones ;-)
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Mesa Boogie MkIVb short head, ADA MP-1 v2, Fractal AxeFX II, Rocktron Velocity 150; Digitech GSP1101, DigiTech 2120Artist, Carvin Tube 100, Yamaha MFC10//
Ibanez RG550RF, Ibanez 540S-LPF DY, Ibanez RGR620TKS, Ibanez RGR620TPS, Ibanez RG550Ltd BK, Ibanez RG7620MSOL, Ibanez RGR465MCA, Ibanez RGR765RCB, Ibanez RG620QMSP, Ibanez RG1420FBHB, Ibanez RGT42MDX, 90s ESP M-II Dlx //
DiMarzio CrunchLab/ToneZone/Gravity Storm/Liquifire/AirNorton/PAF Pro/HfH/ibzUSA F Series pups

MarshallJMP

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Re: Mesa 50/50 lo power issue
« Reply #5 on: Time Format »

From what I can see, the hi/lo switch doesn't change anything to the bias circuit, or am I missing something? It just seems to lower the voltage to the phase inverter.
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Systematic Chaos

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Re: Mesa 50/50 lo power issue
« Reply #6 on: Time Format »

Mine made a crackling sound on one channel when switched to LoPwr. Everything was fine on HiPwr. After I replaced R242 (which was failing) everything was sweet again....
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Mesa Boogie MkIVb short head, ADA MP-1 v2, Fractal AxeFX II, Rocktron Velocity 150; Digitech GSP1101, DigiTech 2120Artist, Carvin Tube 100, Yamaha MFC10//
Ibanez RG550RF, Ibanez 540S-LPF DY, Ibanez RGR620TKS, Ibanez RGR620TPS, Ibanez RG550Ltd BK, Ibanez RG7620MSOL, Ibanez RGR465MCA, Ibanez RGR765RCB, Ibanez RG620QMSP, Ibanez RG1420FBHB, Ibanez RGT42MDX, 90s ESP M-II Dlx //
DiMarzio CrunchLab/ToneZone/Gravity Storm/Liquifire/AirNorton/PAF Pro/HfH/ibzUSA F Series pups

MarshallJMP

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Re: Mesa 50/50 lo power issue
« Reply #7 on: Time Format »

Mmm strange  :o
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Systematic Chaos

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Re: Mesa 50/50 lo power issue
« Reply #8 on: Time Format »

Here's a doc I compiled with some more how-to info including pics on the modification (see attached
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Mesa Boogie MkIVb short head, ADA MP-1 v2, Fractal AxeFX II, Rocktron Velocity 150; Digitech GSP1101, DigiTech 2120Artist, Carvin Tube 100, Yamaha MFC10//
Ibanez RG550RF, Ibanez 540S-LPF DY, Ibanez RGR620TKS, Ibanez RGR620TPS, Ibanez RG550Ltd BK, Ibanez RG7620MSOL, Ibanez RGR465MCA, Ibanez RGR765RCB, Ibanez RG620QMSP, Ibanez RG1420FBHB, Ibanez RGT42MDX, 90s ESP M-II Dlx //
DiMarzio CrunchLab/ToneZone/Gravity Storm/Liquifire/AirNorton/PAF Pro/HfH/ibzUSA F Series pups

Soloist

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Re: Mesa 50/50 lo power issue
« Reply #9 on: Time Format »

Ok, just got my 50/50 back from the shop here was the problem:
Blown grid resistor in channel A, which caused the 3 remaining grid resistors values to stretch out of spec to 500 ohms.
Replaced all 4 grid resistors with 470 ohm , 5w carbon composite resistors.
Now that it is properly fixed, need to tweak all my patches,  since they were made with the mesa being f#&$ed up. Thanks for the assistance guys :thumb-up:
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Live Rig:
Preamps -ADA MP1-ADA MP2-Marshall JMP1-Digitech GSP1101
Post Effects -TC Electronic G Major2-TC Electronics G Force-BBE 482i
Pre Effects -Boss NS 2-Boss GE 7-Radial Engineering Hot British-Ibanez TS9-MXR M108-Boss SD1
Mixing/Switching -Alesis Multimix8-Voodoo Lab GCP-Voodoo Lab Amp Selector- Radial Engineering Big Shot I/O v2
Power - ADA MT200-Mesa 50/50-Voodoo Lab ISO5 Pedal Power-Furman RP8-Livewire PC1100
Axes - Charvel So Cal Pro Mod-Jackson DK2MQ Pro-Jackson USA Soloist-Ibanez RG3XXV
Cabs -4 2x12 ADA Split Stacks

Soloist

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Re: Mesa 50/50 lo power issue
« Reply #10 on: Time Format »

....and a big thanks to SC. I had the deep mod installed while it was in the shop. :headbanger:
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Live Rig:
Preamps -ADA MP1-ADA MP2-Marshall JMP1-Digitech GSP1101
Post Effects -TC Electronic G Major2-TC Electronics G Force-BBE 482i
Pre Effects -Boss NS 2-Boss GE 7-Radial Engineering Hot British-Ibanez TS9-MXR M108-Boss SD1
Mixing/Switching -Alesis Multimix8-Voodoo Lab GCP-Voodoo Lab Amp Selector- Radial Engineering Big Shot I/O v2
Power - ADA MT200-Mesa 50/50-Voodoo Lab ISO5 Pedal Power-Furman RP8-Livewire PC1100
Axes - Charvel So Cal Pro Mod-Jackson DK2MQ Pro-Jackson USA Soloist-Ibanez RG3XXV
Cabs -4 2x12 ADA Split Stacks

Systematic Chaos

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Re: Mesa 50/50 lo power issue
« Reply #11 on: Time Format »

Yeah, the old 50/50 with the Mesa Deep Mod sounds boss :thumb-up:
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Mesa Boogie MkIVb short head, ADA MP-1 v2, Fractal AxeFX II, Rocktron Velocity 150; Digitech GSP1101, DigiTech 2120Artist, Carvin Tube 100, Yamaha MFC10//
Ibanez RG550RF, Ibanez 540S-LPF DY, Ibanez RGR620TKS, Ibanez RGR620TPS, Ibanez RG550Ltd BK, Ibanez RG7620MSOL, Ibanez RGR465MCA, Ibanez RGR765RCB, Ibanez RG620QMSP, Ibanez RG1420FBHB, Ibanez RGT42MDX, 90s ESP M-II Dlx //
DiMarzio CrunchLab/ToneZone/Gravity Storm/Liquifire/AirNorton/PAF Pro/HfH/ibzUSA F Series pups
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