Friday, 5 July 2013

Phase 90 mods

In the summer on 2012 I was looking into a phase pedal. The obvious choice was the Phase 90 by MXR. Now they have a huge selection of phaser pedals. Sadly the one I wanted, script reissue with LED and DC power jack, was pretty expensive. The regular phase 90 was a lot less expensive compared to the script ones. I don't know how but I stumbled across this thing call the script mod. So I've heard of pedal mods before. But I never knew that it was that simple. The Script Mod was basically removing the R28 resistor from the circuit. All I had to do was cut off one of the legs of that resistor. I really like the idea of being able to have a more vintage sounding phaser, but what if I wanted to switch back to the original design if I didn't like it or if the song demanded it. This is where I got the idea of putting in a switch. I'm really glad I put in this switch. To this day I still switch between the stock and script switch to change up the sound. I did this mod last summer and since then I decided to do another mod to the Phase 90, but I'll get into that a little later. Currently my Phase 90 has 2 switches on it. One is the script mod and the other is a tremolo mod. Here are some pictures of my modded phase 90. I'll also give some tips I learned along the way with modding. 

So here it is in its beauty
The V represents vintage and that drawing is just to say what I have done with the circuit. I can switch between having the R28 resistor in or out.
Taking out the PCB isn't that difficult but putting it back in is
Here is the solder side of the PCB. Don't mind the two wires, thats for the tremolo mod
You have to take off all of the nuts before you can take out the board...
....even the jacks
So here I have two tightly fit switches between components
This I believe is a bias knob. DO NOT TURN IT. This will change the sweep and make it sound uneven
Here is the switch for the script mod. I put electrical tape around it to make sure it doesn't short circuit.
There is the placement of the R28. Just above the output jack.
As you can see I desoldered one leg of the resistor and lifted it up.
What you want to do is have a SPST switch. I had to just snap off one leg so when it's in that position the resistor is removed. Have one wire that goes from one lug to the empty whole. Have the next wire that is soldered to the second lug be soldered to the other end of the resistor. This diagram explains it pretty well...I think.

The placement of the switch is important. You want a space that has a low profile so the switch can fit without putting stress on the board.

Next you would want to drill a whole accordingly. 


This is the next mod I decided to do, it's called the Tremolo mod. I found this in the Wampler book of pedal modifications. It's a great book, thats where I found the mod for my Marshall Guv'nor. This mod does as it's supposed to do, tremolo. But in my experience, it has kinda like a univibe characteristic to it. It does phase but it also swells the volume like a tremolo. The one thing that makes this mod not perfect is that at the peak of volume it almost distorts a little. But I can't really tell in the moment.
The mod was to put a 0.1uf cap to touch these two points in the circuit.
For the switch, what I did was have the .1uf cap flush against it for minimal space occupied
As for the placement of the two wires, one wire is attached to one lug of the switch, the other wire is soldered to one leg of the cap, and the other leg of that cap is soldered to the other lug on the switch. I hope thats not confusing. So I have the switch itself on top and the solder on the back. 
 So I can very easily take the two wires and bend the around the corner place where there is room.
Then the switch rests in-between some transistors

A vey snug fit!
So this is my phase 90. I never thought that I could do two mods but look at it now. It's a very versatile pedal for only one knob!
If you have any questions or comments about these mods, please leave them in the comment section below. 

18 comments:

  1. Thank's man, it works great! I also did both of the two mods :D

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    1. No problem, I'm glad I could help someone out! Was this your first mod?

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  2. No, it wasn't. I mounted a switch on my Epiphone valve junior to choose between triode or pentode mode. I builded a Big muff clone with my own designed pcb layout and the new project is: to put the Park G10 combo's sound into a pedal. It was a cheap 10 watts combo with a strange dual gain preamp and with very nice overdrive sound. The pcb layout is already done, I'm gonna build it tomorrow :)

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    1. WOW! Nice! I only asked cause this was my first mod ever

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    2. You can check the pictures about my works if you confirm my friend request on facebook

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  3. What switches did you use? I know it's a SPST, but do you have a part number and/or source? I'm having trouble finding one with a low enough profile.

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  4. I went to me local electronics store to get the switches. In terms of part numbers I have no idea. Usually in the switches description will say like miniature or something like that. If your buying from online I could suggest this one http://www.mammothelectronics.com/4STS-1MS1T2B3M1QE-1MS1T2B3M1QE-p/810-1005.htm by Mammoth Electronics

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  5. is posible do the truebypass mod?

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    1. Hy! Yes, it is possible, but it's difficult because the footswitch is soldered on the main PCB. The only way if you solder out the original switch, after that you cut out it's mounting area from the PCB (to get place for the 3pdt switch). And finally you join the legs of the 3PDT switch with wires to the PCB's correct soldered joint points. I think it has too much chance to do it wrong. It could't worth for me.

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  6. Hi guys, do you know if there is a mod to regulate volume or intensity for this pedal?

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  7. thanks so much..i completed both mods and they work great..i enjoy modding and diy pedals these days..i linked to your blog once i posted pix of the mod i did using your instructions on one of my blogs..credit goes to you good sir

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    1. I'm glad you enjoyed it! Its funny, I haven't posted anything here a really long time, maybe even a year or so. I've been so caught up in school work I completely forgot I had this blog!

      But I'm super glad that I made this thing cause the internet helped me so much in this field of electronics and I wanted to give back. I'm stocked people are still visiting this site!

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    2. yes!..im actually surprised you saw my comment because i noticed it hadnt been responded to in a while,so i said what the heck,i want to comment anyway and show my thanks..i havent posted on my blog on quite a while either..again thanks for the great instructions!

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  8. This comment has been removed by the author.

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  9. Hi Dimitri, Just discovered this blog. Would you consider doing just the script mod on my logo phase 90?I'd be glad to prepay you. I don't trust myself trying it but I remember loving my old script one. wheelsgranata2gmail.com

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  10. Please help, I have just finished a PHASE 90 build with a script mod switch from (SABROTONE) And arm stuck on what switch I must use, is it a on-off-on or another kind. Sorry for this beginner Alert. Thanks Stu.

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