Can anyone provide (or point me to) a diagram and/or instructions for this mod on this pedal specifically? Ideally, I'd also like to change the LED from power status to effect status.
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EHX Bass Micro Synth - DIY True Bypass Mod
- Thread starter EricF
- Start date
[Invalid or Expired Link Removed]
The red 'from input jack' connects to the lug on the jack where the TIP of the plug connects with it.
The Purple 'to output jack connects to the lug on the jack where the TIP of the plug connects with it.
The orange 'to circuit input' is a little trickier. You're going to need to find out which wire running to the circuitboard is the input signal wire. It may run from the old switch. If you get confused with this part, take a picture of the guts and I can help you out.
The blue 'from circuit output' is the same exact thing as the input one, just that it's the output
Take the POWER LED and connect a 2.2k or so resistor to it's LONG lead (the positive lead) if it doesn't already have a resistor. If the long lead is already cut off, you're going to have to turn on the effect and figure out which side is which with a multimeter. Once you've located the positive lead, put the resistor on it and solder it to your power source (the AC jack). Use a wire if it's too short.
Take the SHORT lead (the negative lead) of the LED and connect it to where the neon green is on the diagram: That will disconnect the LED's circuit when the effect is off and turn it off.
Solder a wire to the dark green 'ground' section and lead it to the SLEEVE section of either the input or the output jack.
The 'purple' connection is actually just a wire soldered between those two points.
NOTE: With this diagram, your 3PDT switch should be oriented like this:
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- - -
- - -
not like this:
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If you're not familiar with the way a 3PDT switch works, it's like this. Imagine each column of lugs (in the top 'diagram' I just showed you) is like an independent switch. However, they're all being actuated by the same foot-button. When the switch is 'off', the middle lugs of each 'seperate switch' and the bottom lugs will be connected. See how that purple wire goes around the bottom. When your effect is off, the signal comes from the input jack, then travels through that purple wire and straight to the output jack. Voila. True Bypass. When the effect is ON, the middle lugs become connected with the top lugs, so the signal comes from the input jack, goes through the circuit, comes out of the circuit, and goes to the output jack.
Get it?
The LED switch works a different way. When the effect is OFF, the bottom lug and middle lug are connected. Therefore, the ground of the LED is disconnected, cutting the LED's 'circuit' and not allowing electricity to flow. When you turn the effect ON, the circuit is now complete because the LED's ground connected to something that's common with the rest of your effect...the 'master' ground point.
I'll post more in a bit, but in the meantime order a 3PDT switch. If you don't have any solder, a soldering iron, or wire, do that too. And make sure you can solder alright before you try to modify a $200+ pedal.
The red 'from input jack' connects to the lug on the jack where the TIP of the plug connects with it.
The Purple 'to output jack connects to the lug on the jack where the TIP of the plug connects with it.
The orange 'to circuit input' is a little trickier. You're going to need to find out which wire running to the circuitboard is the input signal wire. It may run from the old switch. If you get confused with this part, take a picture of the guts and I can help you out.
The blue 'from circuit output' is the same exact thing as the input one, just that it's the output
Take the POWER LED and connect a 2.2k or so resistor to it's LONG lead (the positive lead) if it doesn't already have a resistor. If the long lead is already cut off, you're going to have to turn on the effect and figure out which side is which with a multimeter. Once you've located the positive lead, put the resistor on it and solder it to your power source (the AC jack). Use a wire if it's too short.
Take the SHORT lead (the negative lead) of the LED and connect it to where the neon green is on the diagram: That will disconnect the LED's circuit when the effect is off and turn it off.
Solder a wire to the dark green 'ground' section and lead it to the SLEEVE section of either the input or the output jack.
The 'purple' connection is actually just a wire soldered between those two points.
NOTE: With this diagram, your 3PDT switch should be oriented like this:
- - -
- - -
- - -
not like this:
| | |
| | |
| | |
If you're not familiar with the way a 3PDT switch works, it's like this. Imagine each column of lugs (in the top 'diagram' I just showed you) is like an independent switch. However, they're all being actuated by the same foot-button. When the switch is 'off', the middle lugs of each 'seperate switch' and the bottom lugs will be connected. See how that purple wire goes around the bottom. When your effect is off, the signal comes from the input jack, then travels through that purple wire and straight to the output jack. Voila. True Bypass. When the effect is ON, the middle lugs become connected with the top lugs, so the signal comes from the input jack, goes through the circuit, comes out of the circuit, and goes to the output jack.
Get it?
The LED switch works a different way. When the effect is OFF, the bottom lug and middle lug are connected. Therefore, the ground of the LED is disconnected, cutting the LED's 'circuit' and not allowing electricity to flow. When you turn the effect ON, the circuit is now complete because the LED's ground connected to something that's common with the rest of your effect...the 'master' ground point.
I'll post more in a bit, but in the meantime order a 3PDT switch. If you don't have any solder, a soldering iron, or wire, do that too. And make sure you can solder alright before you try to modify a $200+ pedal.
You can even put in a blue LED for extra tone if you want 
Finding the circuit input will be interesting. If the jacks and switch are all board-mounted (soldered directly to the circuitboard) it will be pretty hard for you. If not, it will be a lot easier.
I imagine the current switch in your BMS is DPDT...that is, two 'independent' switches controlled by one foot-button. If it's not mounted to the board, you should see a few wires going to and from the board. If there's only two, those are your input and output wires. If you get confused, just take a pic and post it here and I'll see if I can't figure it out.
Figuring out LED polarity might also be hard (positive and negative leads).
[Invalid or Expired Link Removed]
In this picture, you can see that the LEDs have two leads...one is short, one is long. The long one should be connected to your power source (AC jack, make sure you know which lug on it is your positive/voltage). It's the + side. The short one is the ground, and should be connected as that neon green segment in the diagram I linked you to.
The problem is that most manufactures clip the leads so they don't waste space.
The solution: if the LED isn't board-mounted, you'll see that there are two wires going to it. One wire will probably run directly from the AC jack. In that case, you can leave that wire connected and simply disconnect the ground lead of the LED and reconnect it to your new switch. You won't have to worry about connecting a resistor in that case.
If it IS boardmounted, a lot of manufacturers label on their board which side is positive. Look on the board for a + marking next to the LED's solder point. That will be the positive side. And like I said, if that's the case you don't have to worry about reconnecting it, or putting a resistor on it. Just clip the ground (short) lead, pull it away from the board, solder a wire from it to your new switch.
If it is boardmounted and there's no marking, you could do two things.
a) You know how the actual bulb of the LED has a sort of rim around the bottom? Well, there's a spot on that rim that is sort of sanded flat, that makes it not so circular. If you look at the LED directly from the top, that flat spot on the rim lines up with the ground (short) lead of the LED.
b) Turn on the effect and take your multimeter to it. Connect the ground of the multimeter to the sleeve lug of your input jack, then measure the voltage at each pin. The one with voltage on it is your positive (long) lead.
Any questions?
Finding the circuit input will be interesting. If the jacks and switch are all board-mounted (soldered directly to the circuitboard) it will be pretty hard for you. If not, it will be a lot easier.
I imagine the current switch in your BMS is DPDT...that is, two 'independent' switches controlled by one foot-button. If it's not mounted to the board, you should see a few wires going to and from the board. If there's only two, those are your input and output wires. If you get confused, just take a pic and post it here and I'll see if I can't figure it out.
Figuring out LED polarity might also be hard (positive and negative leads).
[Invalid or Expired Link Removed]
In this picture, you can see that the LEDs have two leads...one is short, one is long. The long one should be connected to your power source (AC jack, make sure you know which lug on it is your positive/voltage). It's the + side. The short one is the ground, and should be connected as that neon green segment in the diagram I linked you to.
The problem is that most manufactures clip the leads so they don't waste space.
The solution: if the LED isn't board-mounted, you'll see that there are two wires going to it. One wire will probably run directly from the AC jack. In that case, you can leave that wire connected and simply disconnect the ground lead of the LED and reconnect it to your new switch. You won't have to worry about connecting a resistor in that case.
If it IS boardmounted, a lot of manufacturers label on their board which side is positive. Look on the board for a + marking next to the LED's solder point. That will be the positive side. And like I said, if that's the case you don't have to worry about reconnecting it, or putting a resistor on it. Just clip the ground (short) lead, pull it away from the board, solder a wire from it to your new switch.
If it is boardmounted and there's no marking, you could do two things.
a) You know how the actual bulb of the LED has a sort of rim around the bottom? Well, there's a spot on that rim that is sort of sanded flat, that makes it not so circular. If you look at the LED directly from the top, that flat spot on the rim lines up with the ground (short) lead of the LED.
b) Turn on the effect and take your multimeter to it. Connect the ground of the multimeter to the sleeve lug of your input jack, then measure the voltage at each pin. The one with voltage on it is your positive (long) lead.
Any questions?
343SB, dude, you're a plethora of knowledge! I'll definitely look you up when I bust this thing open if I come across something I can't figure out. Thanks for all the info. You actually have me thinking that I CAN do it.
You can. It's really cake. A few years ago, I knew NOTHING about electronics.
I'm a little DIY guy compared to Mark Hammer and everyone at DIYstompboxes.com. I know the simpler stuff.
I wouldn't suggest busting it open..there's screws, you know!
Anyhoo, definitely drop me a line, either by PM or just on this thread if you run into any issues.
I'm a little DIY guy compared to Mark Hammer and everyone at DIYstompboxes.com. I know the simpler stuff.
I wouldn't suggest busting it open..there's screws, you know!
Anyhoo, definitely drop me a line, either by PM or just on this thread if you run into any issues.
I wouldn't suggest busting it open..there's screws, you know!
Aw, man. If I gotta use tools, I ain't gonna do it. I figured I could just rip the wiring connections apart and tape them back together in the right places. I even had a special rock I was gonna use to bust the case open.
im looking to make my EHX BMS true bypass. any help?
the page that's linked above is gone. anyone have the instructions or another page to link to?
the page that's linked above is gone. anyone have the instructions or another page to link to?
Aw, man. If I gotta use tools, I ain't gonna do it. I figured I could just rip the wiring connections apart and tape them back together in the right places. I even had a special rock I was gonna use to bust the case open.
lmao
ug, thor want mod!
hey guys, I'm digging this thread out as I would like to do this mod, just bought a BMS (thanks michele 
)
I don't have a camera around so I did a leet smartdraw drawing of the inside. Here goes:
based on Link Removed, I assume that the top brown wire is the buffered output from the board, and the bottom green one is the affected fx output from the board. But he doesn't do his mod with a 3PDT so I'm not sure about the rest
So, if I'm correct, we should rewire the thing like this:
Is this correct? I am not sure at all about this. Can someone jump in and correct me if I'm wrong? Also I am not sure about the led wiring to have it as status, this is how I modded my q-tron for status led, but the q-tron ground was not connected to the chassis of the pedal...
)I don't have a camera around so I did a leet smartdraw drawing of the inside. Here goes:
based on Link Removed, I assume that the top brown wire is the buffered output from the board, and the bottom green one is the affected fx output from the board. But he doesn't do his mod with a 3PDT so I'm not sure about the rest
So, if I'm correct, we should rewire the thing like this:
Is this correct? I am not sure at all about this. Can someone jump in and correct me if I'm wrong? Also I am not sure about the led wiring to have it as status, this is how I modded my q-tron for status led, but the q-tron ground was not connected to the chassis of the pedal...
I believe this would work, if all your assumptions are correct. I should note, however, that I have never seen the inside of a BMS, let alone any kind of a schem.
Unrepresented
Something Borderline Offensive
I have nothing helpful to add to this thread, but did feel like offering up that I paid someone else to do this exact mod to my BMS. 3pdt switch converted to true bypass and LED changed over to status light instead of power.
BTW, anyone wanna speculate on why my BMS had a 3pdt switch already installed but had a reeeeally tone sucking bypass on it standard?
BTW, anyone wanna speculate on why my BMS had a 3pdt switch already installed but had a reeeeally tone sucking bypass on it standard?
Here's the mod I did on mine. The led is wired to turn on when the effects are on, and off when its being bypassed. (instead of power on= lighted up and power off = no light) which i find is quite pointless, cos who turns the power to their pedal off in the middle of playing?
The white wire goes to the hot of the input jack (its under the metal body and thus cant be seen in the pics.)
hope it helps!
The white wire goes to the hot of the input jack (its under the metal body and thus cant be seen in the pics.)
hope it helps!
All the newer ones are like that - I know mine was.
I think it's just for on/bypass level stability. Given the input gain circuit that it uses, perhaps they figured it'd be easier to buffer everything so that there wouldn't be any issues with dramatic volume differences.
Of course, they could've redesigned the whole circuit to work better with basses that cause problems (i.e., active basses, hot passive basses), but then it'd probably cost more.
Just a guess.
cool
post a pic too?
thanks for the other replies. I'll check em out tomorrow, I'm a bit in a hurry right now
Here's the mod I did on mine. The led is wired to turn on when the effects are on, and off when its being bypassed. (instead of power on= lighted up and power off = no light) which i find is quite pointless, cos who turns the power to their pedal off in the middle of playing?
The white wire goes to the hot of the input jack (its under the metal body and thus cant be seen in the pics.)
hope it helps!
hmm I don't like this, it's the opposite as what I am thinking to do if you look at the wire that is supposed to be the board fx output
oh, i was guessing that the effects output from the board was the brown wire and not the green. Was I wrong?
So do i just unsolder hte brown and tape it up, and solder hte green wire in there?
weird, it sounds fine to me by doing this, so i thought i had guessed correctly.
So do i just unsolder hte brown and tape it up, and solder hte green wire in there?
weird, it sounds fine to me by doing this, so i thought i had guessed correctly.
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