# Vintage MXR Phase 90 Question. Again



## Adcandour (Apr 21, 2013)

I was at another forumite's place and he mentioned that what mkes a phaser great is when it's at unity gain and doesn't sound separate from the notes that you are playing. Below, in bold, is the mod he used to get his newer phase 90 to neet the requirement.

This is the issue I'm having with my vintage phaser. The only thing is that it's not the same circuit board. Does anyone have advice of what I need to change to make this happen? I may be able to take it to my guitar tech to perform the mod.

*Some time around when the EVH Phase 90 was brought to market, the orange reissue block
Phase 90′s (with the exception of the Script logo models) began being built using SMT 
components. 

This makes modifications a little tricky. From what I have seen, the component 
numbers are not the same as earlier conventional component models. This means that R28 on a
SMT board is not the same R28 on a non-SMT board. That being said, these mods apply only to
the non-SMT component models. At some point, the block Phase 90′s started
being built again with through-hole components so be sure to check yours before performing any mods. I had the chance to modify a current (2012) Phase 90 that belongs to a friend. Photos of the Rev F board
are below showing the locations of R28, C11 and C12.

Please note before continuing that these mods will NOT turn your reissue in to a script logo 
version. They will however, help improve the sound of the circuit.

The first, and most common mod, is to remove the feedback resistor, R28 (24K). This will make
it sound somewhat like the classic script version and pretty much eliminate the distorted mid-boost. If this is not enough, then remove C11 and C12, this mod will remove the pre and de-emphasis (noise filtering).
On the reissue board photos (below), C11is .01uf & C12 is 680pf. R7 (150k), which controls
output level, is directly above C12 in the photo. If you remove all three (R28, C11, and C12), 
lowering R7 to 130k gives unity gain in most setups. Re-adjusting the trimpot afterwards will
help too. Mark the trimpot first with an index line so you know what the original setting was


Here's some pics. Note they belong to some dude and I'm not the brains taking credit.
































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## sulphur (Jun 2, 2011)

@bduguay @mhammer 

Not much help to you, but I modded a block logo with the three mods and it did make a good bit of difference in that unit.
It seemed less harsh, smoother afterward.


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