Power supply problem
  • Hello everybody,

    i wanna build togehter the smr4 mk II v0.1 filterboard and at step 5 "power supply testing" i have 0,28 V on the red point and 0,08 V on the green probe point.
    Can anybody help me.

  • What is the voltage on the wire jumper labelled “SW” (ie, what is the voltage delivered by your power supply?).

    Looks like your supply is AC, badly polarized, or has a voltage too low for the regulators to operate correctly.

  • I didn´t found a wire jumper in the kit. But in the picture i saw a littel wire (self made), like a bridge. This is what i made too.
    The power supply delivering 9 V.
  • I have a 3-12 V VDC 600mA

    And if i probe this, there 9 V.
  • Picture 1
  • Backside
  • You will have to bridge these two MS Pads….. i can’t see from the Pic if you really did.

  • Could you please post the voltage read at the pads labelled I / O and + (-) of the 7805 and the 7905?

  • There is no bridge in the first picture...so what can i take for this?
  • Use a resistor leg (or any component leg) from something you cut.

  • 7905 = -0,03
    7805 = 0
  • black probe at + and red probe a -.

    sorry...i´m a really beginner.
  • Its really easy: if you don’t bridge the two Pads labeled MS (= Master Switch) it is exactly the same as if you had a Switch and set this to the OFF Position.

    In General most Synths work better with Electricity.

    BTW, the Black Probe always goes to Ground (GND) and you measure with the red one.

  • Ok...the MS is bridged.

    7905 = -0,3
    7805 = 0
  • Voltages are always measured with respect to a reference. You need to put the black probe of the meter on what you want to be your reference, and the red probe on the point whose voltage, respective to the chosen reference, had to be measured.

    In this case, I want to know the voltages at pins, I, O, + of the 7905 and I, O, – of the 7805. These are 6 voltages to measure, all of them relative to the GND pad.

  • Measure of DC Connector 8,93 V and at the MS bridge 8,93.

    I continue to be something as a while ago.
  • ok...i understand.

    7905 I = -0,3
    7905 O = 0
    7905 + = 0

    7805 I = -0,2
    7805 O = -0,2
    7805 - = 0

    in reference to gnd
  • oh...i see now i have changed the 7905 to 7805 and the 7805 to 7905..shit.
    i thought they are both the same.
  • Must be a reason they are labeled different….. ;-)

    Everybody that never swapped a Part raise Hands! None?.....

  • yeah...at the digiboard are beautiful red circles und numbers on the picture... :-)

    but i think nothing is lost...only more work. :-)
  • Have fun desoldering them, they’re possibly the worst things to get out :)

  • Oy ve! I got off easily since I thought I know this after having built lots. My first Shruthi worked fine, but I mixed up some capacitors even though I was being careful and measured everything before soldering. Or so I thought…

    Good thing you spotted it. Have fun!

  • they are out...and now they are in, but the hole was close. I soldered it above but the measure is the same.

    Is it damaged now???

    So there must be a new filterboard and the few parts...i think positive...the board and the parts are cheap.
  • The hole was closed? the hole in the board? you need to use a solder sucker or some wick (sucker is usually best) to clear out the holes.

    Sometimes you need to add a bit more solder to the joint to get it to clear easily.

  • If there’s no sucker and wick won’t help: put the PCB in one hand, soldering iron in another. Melt the solder with iron and quickly hit the board flat side on the edge of the table. Solder will fly out of the hole.

  • yes, the hole in the board (6 holes).
    I have a solder sucker...but i don´t know if it works.

    Now the 7905 and 7805 are on the right place (not during the holes but above the closed holes, works it?)...but the same measure.
  • which measure should be at this six points?
  • I´m from frankfurt if anybody from germany too.
  • *handheb

    YOu can also use the neddel from a syringe to push the melted Solder out of the Hole. The Solder won’t stick on the stainless steel needle.

  • das geht alles...aber die löcher sind dann zu klein um die dicken Stäbe der Teile wieder rein zu bekommen.
  • yo gate, you can eMail me anytime in German but here we strictly stick to english else BAAAAD THINGS ARE GONNA HAPPEN!!!

    I always have 0,5mm, 0,8mm and 1,2mm needles on stock – the girl in the Pharmacy every time looks like if i was a junkie until i recently showed her my arms ;-)

  • > which measure should be at this six points?

    O: -5V
    I: -9V (might change depending on your power supply, but should be in the -12 .. -7 V range)
    +: 0V (grounded)

    O: 5V
    I: 9V (might change depending on your power supply, but should be in the 7 .. 12 V range)
    -: 0V (grounded)

  • @fcd72
    Haha! When i buying lye and acetone clerk at hardware store looks at me same manner =)

  • Oh sorry!

    I write you an email.

    And thank you all for the support.
  • if there other measures...where is the mistake?
    How can i find out?
  • Have you check for shorts between adjacents pins of the regulators? You should at least see I: 9V on the 7805, because it’s directly hooked to the power supply.

    Which voltage do you have on the “I” pin of the 7805?

  • 7805 I = 0
  • So 9V at SW?, but nothing at I? Maybe you have soldered the protection diode backwards?

  • The white stripe is correct. Where the white strip is are 0 V and on the other side close to the DC connector, however, are 9 volts.
  • Is there a way for you to change the polarity of the power supply? Maybe you are measuring backwards and the power supply has the wrong polarity?

  • i can change between 3 till 12 V.

    I thought i need 9 V, not?
  • 9V, yes, but what about the polarity?

  • The polarity is + o -
  • http://www.conrad.de/ce/de/product/518370/VOLTCRAFT-USPS-600-STECKER-SCHALTNETZT/SHOP_AREA_17455&promotionareaSearchDetail=005
  • If you put the black probe on outside of the barrel connector from the power supply and the red on the inside, does it say +9V or -9V?

  • it say - 8,92 V
  • Ah, then you have negative centre. See what happens if you remove the round barrel connector (hohlstecker) from the flat-ish power supply cord connector, rotate it 180 and put it back on the cord connector.

  • ok...now i have 4,56 V on the protection diode and 3,45 V on the 7805 I....and it was getting very hot so i had to pull the supply off.
  • oh...i see there two connectors of the 7805 soldered.
    the reason of getting hot?
  • embarrassing!
  • IT WORKS...all measures (- 5 at green und + 5 at red points) corect.

    Thank you for walking this way with me!

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