Phase 90 r28 mod story - strange

Discussion in 'Effects, Pedals, Strings & Things' started by SocraticTele, Dec 17, 2009.

  1. SocraticTele

    SocraticTele Member

    Aug 6, 2009
    Akron, OH
    I received my very first phase pedal last week – an MXR Phase 90 block. I’ve never really used a phase pedal before, but I’ve wanted one for a long time. To tell you the truth, I thought I’d only use it occasionally, so it wasn’t high on my list of pedals to acquire. But I managed to get one on a trade for a Sparkle Drive I wasn’t using anymore (I have an Ethos TLC on the way). Anyway, this little pedal has made a HUGE difference in my sound. Like I said, I thought I’d only be using it every now and then – maybe for spacey Floyd-esque type sounds, which I love, but don’t really use very often in a performance environment. However, I’m using it a lot, and I love what it adds to my sound, both for rhythm and lead. I play in a funk/fusion/r&b band, and the Phase90 kicks out the rhythm parts from them mix and adds the perfect, subtle texture. Add a bit of overdrive, and the leads sounds amazing too. I have it set at about 10 o’clock most of the time.

    So, I have a weird story about doing the R28 mod. that I thought I’d share. I had read up a lot about this mod before the pedal had arrived, and it had received high recommendations, so I decided to do it. Now, I’m by no means an electrical engineer, but I have built a number of BYOC pedals, and I make most of my own cabling, so I know how to use a soldering iron. The resistor was, as expected, difficult to get at just with snips, so I turned the board over, carefully marked where the appropriate solder point was, and unsoldered one of the resistor legs enough to pull it most of the way out of its hole. At that point it was easy to snip off both legs of the resistor from the top. Great, I thought – that seemed easy. But when I put the pedal together – disaster: the LED would come on when the pedal was engaged, but the pedal wouldn’t phase the signal. It would only pass a clean sound whether the pedal was off or on. So I took the Phase90 apart once again and closely looked it over to see if I had done something wrong. Did I pull the wrong resistor? Did I drop solder anywhere? Did I loosen something? Everything looked good, so that was weird. I next plugged the guitar into the board and then into the amp, just to see if maybe adjusting the trim pot would make a difference (you can only adjust the trim pot while playing if the pedal is out of its housing). Adjusting the trim pot made no difference at all, however. Still just an unphased, clean signal. I was just about to give up when I noticed something: when I picked the board up off of my knee to put it on my workbench, it suddenly started phasing for a second. I put the board back down on my knee, and the phasing stopped. I picked it up again, and once again got phasing though somewhat intermittently. I soon realized that I was getting the phasing whenever one of my fingers was making contact with a few of the solder points near the output jack. I would place the pad of my index finger on that group of solder points and would get phasing; I’d lift my finger, and the phasing would stop. I decided that I would get a small piece of wire and see if I could recreate the effect by locating the two pads that needed to be connected – perhaps they needed a jumper, I reasoned. So I put the board down to get the wire, but then I noticed something strange – now, even though I was no longer holding my finger against the solder side of the board, I could still hear the pedal phasing my 60 cycle hum from the guitar (I hadn’t turned down the volume on my Strat, serendipitously). The pedal was working again. I picked it up, touched my finger to the solder points, and it still worked. I removed my finger, and again it still worked. I shook it a little bit, and it still worked. So I shrugged my shoulders, put it back in its case, and put it on my board, where it has been residing, trouble-free, ever since. Go figure.
  2. Musikerochan

    Musikerochan Member

    Jan 7, 2009
    cool story bro.


    actually i have one, a P90 build from tonepad. a few weeks ago....

    long story short, i just desoldered r28 altogether. :D
  3. itkindaworks

    itkindaworks Member

    Apr 16, 2008
  4. paintbox

    paintbox Guest

    My version of the that story is I know jack about electronics, got instructions off the net, snipped the resistor in two seconds, put it back together and it did just what i had hoped- sounded much better. No issues at all.

    I have since acquired an actual Script 90 and kind of miss my r28 90.
  5. stinkfoot

    stinkfoot Member

    Jun 20, 2004
    Uppsala, Sweden
    This is why you should snip the resistor off, not desolder it. On the Phase 90 pcb, all holes are through-plated, so the solder will stick to the inside walls of the holes as well. This means that removing components can be real tricky, and it's easy to damage the through-plating if you don't get 100% of the solder out. And to make matters worse, one of the holes for R28 also acts as a through-point (carrying the track from one side of the board to the other), which means that if you damage it, you'll end up with a dead phaser (as you noticed).


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