true bypassing a Phase 90

[Joe Hart]

How do I know if I have a reissue? It's just a Phase 90 that I bought from Musician's Friend in 2004. But it didn't specifically say "reissue" anywhere.

Also, what is the LED change that people talk about? All I can find is that people change the LED to blue. I can only guess that this is for purely aesthetic purposes? But I don't know.
-Joe Hart

[Fret Wire]

The Dunlops (which you bought) are the reissue's. The pcb, jacks, switch, and pot are all pcb mounted on the reissues. The last true MXR Phase 90's were made in the early 80's. They had  separate panel mounted DPDT switch, jacks, pot, and led. The ckt board was separate, loose, and wrapped in foam to prevent shorting out on the box. They are easy to true bypass.

Changing the LED is for asthetic reasons only. I've stuck orange led's in them to match the paint job. Looks better to me than blue. Besides, on a dim lit stage, it better that all your fx don't have the same color leds. If you stick a high bright blue in a reissue, you'll also have to change the led resistor to a higher value. Otherwise, it will be too bright.

Opposed to the R28, C11, and C12 mods, which can be removed by just cutting the leads, changing the led/led resistor involves desoldering, which isn't fun on these pcb's with their plated thru holes. Braid actually works better than the solder sucker pumps do. That's another reason I'd stick with a regular, standard solid color led such as orange. It requires no resistor change, one less part to desolder.

[vanhansen]

Joe, you have a reissue.   Mine is from the late 90's but I had an 80's one when I was in college and ended up selling it.  :cry: If it was made by Dunlop, it's a reissue.

As Fret Wire said, yes there is some tone sucking with the reissue but I don't see hacking it up to make it TB as being worth it IMO.  It's much easier to make a TB box which can be of greater benefit with other pedals being in the same chain.

[Fret Wire]

As Fret Wire said, yes there is some tone sucking with the reissue

Before anyone gets confused, let's point out that all phase 90's, whether of MXR or Dunlop manufacture, are not true bypass, and will suck tone to a degree. The original script model used a Carling single pole switch, the original block logo LED models used the double pole switch. They only require either a DPDT switch (non-led models), or a 3PDT switch (led models), plus rewiring to make them true bypass. Much less work, and far more reward.

Plus, mod nomenclature such as "R28", etc. don't apply to the originals, the boards aren't labeled. You have to describe those components by their actual ckt function. Or trace out the board to find them.

[dadude]

I agree 192.34% with the anti-true bypassing by way of gutting. But if you want to do it this might help.

http://photobucket.com/albums/y229/stompboxsteve2112/Phase%2090/

[tone_crafter]

Hey dadude is that an ordinary phase 90 because it looks different to the other pic on here. Which trace do I need to cut? I can't see it in the pic is it on the top?

Also I want to change the LED. Which resistor to I need to change. Is the resistor soldered on the bottom for the LED?

I also want to true bypass a super comp so I'm hoping the layout isn't too differnt.

[tripp2k]

Hi...newby here and frankly not adventurous enough to take on electronically adjusting a new P90 I have ordered.  Please don't shoot me for being a wimp.  So some questions to the experts:

1) For the purists who know the script sound, would it be better to mod a P90 reissue or are there designers who have achieved a purer "copy" through gutting and replacing all components internally?
2) I am interested in true bypass so in either of the cases in #1, which is the preferred path?
3) Are there any companies or individuals who will make the appropriate mods or replace the guts of my P90 so I can have a purist script P90 with TB? I've seen FXDoctor, but are there others?

Thanks. It's been a pleasure reading through your posts on this topic. tripp.payne@comcast.net

[Dirk_Hendrik]

I did a TB job on RI MXR's a couple (as on customer order) of times with the original switch. (so without sawing a piece out of the board. It does require:
- Your soldering skils up to the max and preferaby a little bit more.
- Full insight in the electronics goinfg to that switch
- A Millennium or similar type approach for the LED
- A dremel for cutting PCB traces
- A multimeter in resistance position

Or, ore specifically, Youll need to desolder the swich without pulling the pads out of the double sided board, cut all PCB traces going to that switch, using a multimeter to verify ther're isolated, including the ones that connect to ground, then resolder the switch and add TB in the Millennium principle.

If any of the 5 points above aren't in your arsenal just don't do it or you'll end up with nothing but trouble. Or, honestly, True bypass is too overrated to apply to these pedals considering the trouble.

[jaysg]

Sounds like some of you might be better off building the BYOC ScriptPhaser.

I do have a question -- anyone know what the year was when MXR changed from Script to Block?  I had a P90 that must have been a Script.  I tried a '79 once and couldn't stand it.

[tripp2k]

BYOC for the Scripter has been ordered and I look forward to it.  I was hoping to keep the MXR box and may see if I can gut and retrofit once I have nice sounding guts. If anyone has done this, please chime in with advise or if you are willing to do it yourself (no offense to our friends across the pond) here in the US with US shipping costs, let me know what you charge. Again, I appreciate the information here and the folks who offer it up.