freestompboxes.org

I have a friend coming to town with his Boss PH-1R, which needs fixing. He's going to be here too short a time for me to reverse it and still drink beer with him.

Does anyone have the schematic for the PH-1R? I have most Boss schematics, but not that one.

hi rg,

i have the ph1 schematic and layout, please send me a p.m. with your email-adress!


regards, ksui

R.G. wrote:I have a friend coming to town with his Boss PH-1R, which needs fixing. He's going to be here too short a time for me to reverse it and still drink beer with him.

What ? Drinking beer instead of reversing ?

at least you could take some photos for later reversing, since...

Does anyone have the schematic for the PH-1R?

sorry, I have only the schematic of the PH-1 a traced one and an original.

I have most Boss schematics, but not that one.

You are not alone....I think all of the world is waiting since years to see a schematic of the PH-1R.

analogguru

Hey RG, found a HC msg from you, I'll hunt this one out for you.

alteredsounds wrote:Hey RG, found a HC msg from you, I'll hunt this one out for you.

Thanks, I appreciate it.

I turned up top and bottom pics but not a schemo yet.

I'm not going to be able to get many of the component values from the photos I have, but I can tell a few things from the pictures now.

One is that the PH-1r uses the drain-feedback style of voltage variable resistor JFET; this is like the MXR Phase 45 circuit instead of the Phase 90.

Apart from the feedback resistors to linearize JFETs, probably THE other most important aspect is HOW the regeneration pot is connected, i.e. from output of the fourth stage to .........

If anyone knows please fill in the blank

estragon wrote:Apart from the feedback resistors to linearize JFETs, probably THE other most important aspect is HOW the regeneration pot is connected, i.e. from output of the fourth stage to .........

... the inverting side of the first opamp.

are these built with obsolete parts? can one build a clone?

R.G. wrote:

estragon wrote:Apart from the feedback resistors to linearize JFETs, probably THE other most important aspect is HOW the regeneration pot is connected, i.e. from output of the fourth stage to .........

... the inverting side of the first opamp.

Thanks, R.G.

At least the PH-1R is different from other phasers. I checked Ibanez PT-90, Pearl Phaser and Korg PHS-1 schems, and feedback goes from 4th phaser output to the minus input of the SECOND phase stage instead.

I don't have an MXR P-90 schem at hand, but IIRC it is just like I just mentioned as well.

With Ry's help, I've completed tracing out the PH-1r from the picture links he posted.

I'll get it posted to GEO as soon as I've gotten most of the sticks, pebbles and bugs combed out of it.

Notable things about the PH-1r compared to other phasers.
1. They divide the incoming signal down by half to get a lower signal level into the phase line. It's later amplified back up in the final mixer. This approach makes it a bit more prone to noise, but kills some distortion. I have seen phasers that compand around the phase line. That would probably help, at the expense of another chip.
2. They use drain feedback to linearize the phase FETs, as in the P45 but not the P90.
3. They do a really odd connection of their power adapter jack that floats the - side of the power adapter jack one diode plus the drop on a 100R resistor below signal ground. This is not a mistake in my tracing, as I initially thought it was. The factory PH-1 schemo has the same thing. What that means is that these pedals may not work and play all that well with other pedals when they are all daisy chained onto a single large DC power supply. I'm still mulling over what if anything needs done to that.

The parts are garden variety, easy to obtain as long as you can match JFETs (see the matcher at GEO).

On the regen point, I told you wrong. It goes to the noninverting input of the first opamp. The input goes to the inverting input after a transistor buffer.