Roland Jet Phase incoming!

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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chicago_mike
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Post by chicago_mike »

I have a Roland JetPhase AP-7 coming in the mail today. Does anybody need any measurements or anything from it?
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Post by aionios »

I would love to get the specs of the matched JFETs! Vgs(10k), Vgs(off) and Idss if you’re able. I’m curious to see how the voltages match up with something more common
    like the Phase 90. I saw some taken from a unit awhile ago that were in the 0.7-0.8v range, which seemed really low to me - so I’m wondering if that was an anomaly or pretty standard.
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    Post by modman »

    We have a thread on the Roland Jet Phaser here: viewtopic.php?f=1&t=589
    Links to service notes etc...most of the links to guts are dead though...
    Please, support freestompboxes.org on Patreon for just 1 pcb per year! Or donate directly through PayPal

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    Post by chicago_mike »

    aionios wrote:I would love to get the specs of the matched JFETs! Vgs(10k), Vgs(off) and Idss if you’re able. I’m curious to see how the voltages match up with something more common
      like the Phase 90. I saw some taken from a unit awhile ago that were in the 0.7-0.8v range, which seemed really low to me - so I’m wondering if that was an anomaly or pretty standard.
      Im cool with helping out!! Whats the easiest way to measure the fets ?
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      Post by aionios »

      The Vgs(10k) measurement is the most important one for phasers - there's a super simple circuit here that could be breadboarded:
      http://www.geofex.com/article_folders/f ... tmatch.htm

      Vgs(off) (which is basically the same as Vp) and Idss can be taken with another circuit:
      https://tagboardeffects.blogspot.com/201 ... tcher.html
      (The 2nd one on this page is much simpler and should work the same)
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      Post by chicago_mike »

      Cool.

      I should test ALL fets in the phase section yes? Not just like 2 - 4 ?
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      Post by aionios »

      chicago_mike wrote:I should test ALL fets in the phase section yes? Not just like 2 - 4 ?
      Yep. An average Vgs is helpful, but also knowing the spread of lowest to highest, to know what Roland considered to be matched well enough for the circuit.

      MXR was satisfied with up to 0.1V for the Phase 90, which is pretty wide, but matching 8 JFETs instead of 4 is even trickier so I’m curious if it’s tighter or broader than that.
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      Post by chicago_mike »

      breadboarding an Arduino fet tester for this. Should have the jets testedasap!
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      Post by aionios »

      chicago_mike wrote:breadboarding an Arduino fet tester for this. Should have the jets testedasap!
      Oh awesome! Which one is it?
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      Post by chicago_mike »

      this one:

      https://create.arduino.cc/projecthub/pl ... ter-dbafb4


      I didnt really know there were others :hmmm:
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      Post by chicago_mike »

      Okay I posted my initial FET measurements. Only for the 8 phasing FETS right now.

      When I get more time, I take measurements of the other fets
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