MXR Phase 100

lowell · 01-05-2009, 06:40 PM

I have an MXR Phase 100 that I've been working on. It came to me completely broken, but I got the phase effect to work. The problem is it is distorted. I have done the diode check on all the transistors and checked voltage on all the op amps, and nothing comes out abnormal. Could anybody offer some advice as to what I might look for next?

Mark Hammer · 01-06-2009, 03:11 PM

Under what circumstances is it distorted, and could you perhaps describe the nature of the distortion a bit more?

Note that since the P100 uses optoisolators instead of FETs like the P90, there should be no distortion resulting from things like misbiased FETs. As well, since it does not use JFET switching like a great many other commercial phasers, there should be no distortion from that source either.

lowell · 01-15-2009, 07:33 PM

It is distorted when the effect is on. The effect works but there is a buzzy distortion the whole time.

lowell · 06-19-2009, 10:42 PM

I've gone through and replaced all the opamps, transistors, and optos in this thing. The effect works but is still very distorted. The distortion is of a screechy sort. Sounds awful. What would I be looking for here?

lowell · 06-22-2009, 08:59 PM

Ok I got a schem and layout for this pedal on General Guitar Gadgets and they do not match. The schem shows that R53 is grounded but in fact the layout shows it is connected to the 9V supply

Anyone know which is correct? I've filled out their contact form but no reply yet.

olddawg · 06-25-2009, 08:27 AM

Are you using a battery or a power supply? I have an old 70's Phase 100. There are several versions though. There are lots pf gut shots on Google Images.

lowell · 06-25-2009, 09:26 AM

hey i was over on diystomboxes.com w/ this one... forgot I posted here. I figured it out... after many days of pulling my hair out, it happened to be a tiny hair sized piece of teflon wire shorting something.

01-05-2009, 06:40 PM	#1
lowell Senior Member Join Date: Jun 2007 Posts: 1,120	MXR Phase 100 I have an MXR Phase 100 that I've been working on. It came to me completely broken, but I got the phase effect to work. The problem is it is distorted. I have done the diode check on all the transistors and checked voltage on all the op amps, and nothing comes out abnormal. Could anybody offer some advice as to what I might look for next?

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01-06-2009, 03:11 PM	#2
Mark Hammer Senior Member Join Date: May 2006 Posts: 1,116	Under what circumstances is it distorted, and could you perhaps describe the nature of the distortion a bit more? Note that since the P100 uses optoisolators instead of FETs like the P90, there should be no distortion resulting from things like misbiased FETs. As well, since it does not use JFET switching like a great many other commercial phasers, there should be no distortion from that source either.

01-15-2009, 07:33 PM	#3
lowell Senior Member Join Date: Jun 2007 Posts: 1,120	It is distorted when the effect is on. The effect works but there is a buzzy distortion the whole time.

06-19-2009, 10:42 PM	#4
lowell Senior Member Join Date: Jun 2007 Posts: 1,120	I've gone through and replaced all the opamps, transistors, and optos in this thing. The effect works but is still very distorted. The distortion is of a screechy sort. Sounds awful. What would I be looking for here?

06-25-2009, 08:27 AM	#6
olddawg Senior Member Join Date: Dec 2007 Posts: 492	Are you using a battery or a power supply? I have an old 70's Phase 100. There are several versions though. There are lots pf gut shots on Google Images.

06-25-2009, 09:26 AM	#7
lowell Senior Member Join Date: Jun 2007 Posts: 1,120	hey i was over on diystomboxes.com w/ this one... forgot I posted here. I figured it out... after many days of pulling my hair out, it happened to be a tiny hair sized piece of teflon wire shorting something.

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