MXR Phase 90 mods help ?

HOTTUBES · September 04, 2011, 03:31:21 PM

I have a MXR PHASE 90 that i want to do the standard " R-28" mod to .

But the problem i'm having is identifying the board & its components , my board looks nothing like all other's
that i have seen on the net etc etc , its a strange looking affair with 3 op amps running up the middle of the board ,
and thy are a silver top TLO62CP ,it also has a white trim pot located in the upper left corner of the board.
This board is not labeled .....

i'm assuming this is an older version ........

Any help would be cool !!
Thanks

Govmnt_Lacky · September 04, 2011, 03:38:45 PM

Pictures help in situations like this

EDIT: I have seen one with that layout by doing a Google image search. Unfortunately, I cannot view Flickr images at work

Its there though. Still, a picture of yours would speed things up a lot!

HOTTUBES · September 04, 2011, 08:02:52 PM

Ok , so same general layout as this one .

Does anyone know how to mod this type of board ?

iccaros · September 04, 2011, 08:10:55 PM

I would look at the schematic http://www.geofex.com/FX_images/p180.gif and start with a DMM and trace it out.
Make a photocopy of the board and mark where connections match the schematic, and then plan your mod.

Joe Hart · September 04, 2011, 08:53:15 PM

Does your pedal have any "vintage" value and maybe shouldn't be altered? Just a thought...
-Joe Hart

HOTTUBES · September 04, 2011, 10:05:03 PM

No i don't think it has any vintage value , it has a LED , and its a block letter pedal ....

serial # H7-11780

I know nothing about this pedal in term's of its dating by serial #.

HOTTUBES · September 04, 2011, 10:08:47 PM

I also plan to put a newer style DC jack in this pedal , cause it has the older style Ibanez 1/8 th in plug .

zombiwoof · September 05, 2011, 02:28:07 PM

Quote from: HOTTUBES on September 04, 2011, 10:08:47 PM
I also plan to put a newer style DC jack in this pedal , cause it has the older style Ibanez 1/8 th in plug .

Instead of changing the DC jack, you can get a short adapter cord for around $4-5 that allows you to use a Boss-type adapter with a pedal that has the 1/8" jack on it. There are a couple of companies that make these. I use them for all of my old pedals with 1/8" jacks on them. Here's one:

http://www.ebay.com/itm/C35-1SPOT-ELECTRO-HARMONIX-IBANEZ-BOSS-MXR-DOD-KEELEY-/130539368627?pt=Guitar_Accessories&hash=item1e64c0b0b3

I had the same problem as you doing the mod, as I have an early Dunlop Phase 90 that has that type of board in it. There used to be a really good page on the net that showed all the different boards that the Phase 90 had over the years, with the components listed and marked, but I think the guy took it down. That's how I modded mine, using the directions in the Layouts Gallery here for the full Phase 90 Script mods (there's more than just changing the one resistor). Sorry I don't have the info anymore.

Al

HOTTUBES · September 05, 2011, 03:13:40 PM

bump !

HOTTUBES · September 05, 2011, 10:39:14 PM

Any help would be much appreciated !!

Thank you !

Govmnt_Lacky · September 06, 2011, 07:09:03 AM

If all you want to do is the R28 mod (which may be a different resistor number in this layout), all you need to do is trace the circuit according to the schematic and find where the resistor is. IIRC it is either 22K or 24K.

Use the Tonepad schematic here: http://www.tonepad.com/getFile.asp?id=42

HOTTUBES · September 06, 2011, 10:22:39 PM

Quote from: Govmnt_Lacky on September 06, 2011, 07:09:03 AM
If all you want to do is the R28 mod (which may be a different resistor number in this layout), all you need to do is trace the circuit according to the schematic and find where the resistor is. IIRC it is either 22K or 24K.

Use the Tonepad schematic here: http://www.tonepad.com/getFile.asp?id=42

Its looking like i may have too ...............
Wow , this must be a odd ball board / low production unit ....

zombiwoof · September 07, 2011, 02:18:54 PM

Quote from: HOTTUBES on September 06, 2011, 10:22:39 PM
Quote from: Govmnt_Lacky on September 06, 2011, 07:09:03 AM
If all you want to do is the R28 mod (which may be a different resistor number in this layout), all you need to do is trace the circuit according to the schematic and find where the resistor is. IIRC it is either 22K or 24K.

Use the Tonepad schematic here: http://www.tonepad.com/getFile.asp?id=42

Its looking like i may have too ...............
Wow , this must be a odd ball board / low production unit ....

Not really an oddball board, there were several changes in the board configuration over the years with the Phase 90. Too bad that page I mentioned that showed the different versions seems to be gone now, as it detailed the changes over time with the Phase 90.

Al

Güero · September 07, 2011, 02:27:18 PM

I think that this is the actual schematic for your Phase90....I saw a 25K trimpot in your board....I don't check the resistors. Sure that the 50n capacitors are the 47n in schematic.

HOTTUBES · September 08, 2011, 09:48:58 AM

Thank you !!!!!!!!!!!!!!!!!

zombiwoof · September 08, 2011, 12:35:03 PM

Quote from: Güero on September 07, 2011, 02:27:18 PM
I think that this is the actual schematic for your Phase90....I saw a 25K trimpot in your board....I don't check the resistors. Sure that the 50n capacitors are the 47n in schematic.

This is the schematic I used to mod my Phase 90. I did the ones listed under "Script Mod" but none of the ones under "Other Mods". Turned out really well. As I said, I had an early Dunlop Phase 90 with a board similar to the OP's (not the recent Dunlop board with board mounted jacks and switch).

Al

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MXR Phase 90 mods help ?