Tech: Stern F2K +5V logic fuse blow

Archived from groups: rec.games.pinball (More info?)

OK, I wanted to keep this short but provide enough details, so please bear
with me. First, all boards (MPU, SDU, Power Supply) have been rebuilt and
ground mods done. Voltages on all test points are accurate as per Marvin's
site. Sound board is not hooked on, but the speech board works. Problem:
I'm blowing fuse F3 on the power supply board that supplies the +5V logic to
the MPU when the left upper solenoid switch is activated. The easiest way
to isolate and cause the problem:

1. All connectors are hooked up to the power supply and MPU
2. Disconnect J2 from the SDU to prevent power going to the solenoids
3. Disconnect J4 from the SDU to prevent solenoid logic from getting into
the SDU
4. Starting it up, works fine. Switches cause no errors
5. Now, shutdown and plug in J4 to start the solenoid bank logic going to
the SDU
6. Everything works again, but as SOON as I trip the switch for the left top
kicker, F3 on the power supply blows and I lose the +5V

This is one of the continuous solenoids. I have replaced all major parts in
this line on the SDU board (U2, U4, TIP102, 1N4004) - same results. The
resistors all test out as expected, and the ceramic cap by the TIP102 tests
good as well, so there aren't any other parts I can see to replace.

The diode and capacitor on the switch itself have been replaced as well. I
also swapped U10 and U11 on the MPU in case one of them was bad - same
results. When I previously had all the solenoids hooked up, the playfield
fuse would eventually blow as well and the solenoid would be locked on
(unplugging the pin obviously prevented the lock).

Any ideas on what to check next? Could it be something on the MPU causing
this surge? Something on the power supply? Under the playfield? Any ideas
anyone has would be most welcome at this point - I'm fresh out. Thanks.

- Sean
9 answers Last reply
More about tech stern logic fuse blow
  1. Archived from groups: rec.games.pinball (More info?)

    Does it fire the solenoid/start to fire it before the fuse blows? So
    it only blows the +5 fuse when it goes to fire the solenoid? Do you
    have the diode on backwards, is the coil good? Also, what happens if
    you ground the solenoid manually with a ground wire, do you still lose
    the +5? If you do, the diode is backwards or bad or miswired. (Or the
    coil itself is bad). If you don't, take a look at the work on the
    power supply board. Did it work before the power supply board was
    modified? (I only do about 1/2 the mods Clay suggests for the stern
    version of the power supply board, I don't think some of the back to
    front work is necessary as the stern version has beefier traces vs. the
    bally board)

    Do you have any other boards you can try in the machine, (Solenoid
    driver/power board)?
  2. Archived from groups: rec.games.pinball (More info?)

    The fuse blows before it even fires the solenoid. The fuse is blown
    when the switch is activated - solenoid is never fired. The playfield
    solenoids aren't even hooked up (by removal of J4 on SDU), and prior to
    that I swapped the lines on two different solenoids, results being the
    "bad" one working and the good one not working. So, I've ruled out a
    solenoid related problem.

    The machine never worked - the power supply was completely blown out
    and there were even wires run from the power supply test points
    directly to the SDU. Only spare boards I have are sound and speech.
    I'll double check the work on the power supply.

    seymour-shabow@excite.com wrote:
    > Does it fire the solenoid/start to fire it before the fuse blows? So
    > it only blows the +5 fuse when it goes to fire the solenoid? Do you
    > have the diode on backwards, is the coil good? Also, what happens if
    > you ground the solenoid manually with a ground wire, do you still lose
    > the +5? If you do, the diode is backwards or bad or miswired. (Or the
    > coil itself is bad). If you don't, take a look at the work on the
    > power supply board. Did it work before the power supply board was
    > modified? (I only do about 1/2 the mods Clay suggests for the stern
    > version of the power supply board, I don't think some of the back to
    > front work is necessary as the stern version has beefier traces vs. the
    > bally board)
    >
    > Do you have any other boards you can try in the machine, (Solenoid
    > driver/power board)?
  3. Archived from groups: rec.games.pinball (More info?)

    Correction - J2 to the solenoids on the SDU isn't hooked up. J4 logic
    line is hooked up.

    sean wrote:
    > The fuse blows before it even fires the solenoid. The fuse is blown
    > when the switch is activated - solenoid is never fired. The playfield
    > solenoids aren't even hooked up (by removal of J4 on SDU), and prior to
    > that I swapped the lines on two different solenoids, results being the
    > "bad" one working and the good one not working. So, I've ruled out a
    > solenoid related problem.
    >
    > The machine never worked - the power supply was completely blown out
    > and there were even wires run from the power supply test points
    > directly to the SDU. Only spare boards I have are sound and speech.
    > I'll double check the work on the power supply.
    >
    > seymour-shabow@excite.com wrote:
    > > Does it fire the solenoid/start to fire it before the fuse blows? So
    > > it only blows the +5 fuse when it goes to fire the solenoid? Do you
    > > have the diode on backwards, is the coil good? Also, what happens if
    > > you ground the solenoid manually with a ground wire, do you still lose
    > > the +5? If you do, the diode is backwards or bad or miswired. (Or the
    > > coil itself is bad). If you don't, take a look at the work on the
    > > power supply board. Did it work before the power supply board was
    > > modified? (I only do about 1/2 the mods Clay suggests for the stern
    > > version of the power supply board, I don't think some of the back to
    > > front work is necessary as the stern version has beefier traces vs. the
    > > bally board)
    > >
    > > Do you have any other boards you can try in the machine, (Solenoid
    > > driver/power board)?
  4. Archived from groups: rec.games.pinball (More info?)

    F3 on the power supply board is blowing - the one supplying the 12vdc
    unregulated. I removed the header from the SDU that supplies the coil
    pulldown from the transistors so they're not being energized at all.
    If you can catch the start of the tread, there's some additional info
    in there that may help pinpoint something more specific. Thanks Ray!

    - Sean
  5. Archived from groups: rec.games.pinball (More info?)

    Possible the coil in question has a shorted diode, or is dead shorted
    internally, and when the circuit board activates the transistor to fire this
    coil (switch it to ground), the excessive current due to the short fries the
    fuse (should be solenoid fuse F4 on fuse/rect board or the 1a slo-blow fuse
    under the playfield).

    I missed the start of this thread so not sure exactly which fuse you have
    blowing- there's really no such thing as a "5v logic fuse" in these games.
    There are 5 on the fuse/rectifier board- displays, switched lamps, 12vdc
    unreg. for 5vdc regulator input, solenoid main power, and line voltage.
    (F1-F5 respectively). Which one exactly is blowing?

    Ray J.
    --
    Action Pinball & Amusement, LLC
    Salt Lake City, Utah USA
    Web: www.actionpinball.com

    We're serious about pinball. Anything else is just for fun!


    "sean" <sspindler@ameritech.net> wrote in message
    news:1123162649.303077.106430@g44g2000cwa.googlegroups.com...
    > Correction - J2 to the solenoids on the SDU isn't hooked up. J4 logic
    > line is hooked up.
    >
    > sean wrote:
    > > The fuse blows before it even fires the solenoid. The fuse is blown
    > > when the switch is activated - solenoid is never fired. The playfield
    > > solenoids aren't even hooked up (by removal of J4 on SDU), and prior to
    > > that I swapped the lines on two different solenoids, results being the
    > > "bad" one working and the good one not working. So, I've ruled out a
    > > solenoid related problem.
    > >
    > > The machine never worked - the power supply was completely blown out
    > > and there were even wires run from the power supply test points
    > > directly to the SDU. Only spare boards I have are sound and speech.
    > > I'll double check the work on the power supply.
    > >
    > > seymour-shabow@excite.com wrote:
    > > > Does it fire the solenoid/start to fire it before the fuse blows? So
    > > > it only blows the +5 fuse when it goes to fire the solenoid? Do you
    > > > have the diode on backwards, is the coil good? Also, what happens if
    > > > you ground the solenoid manually with a ground wire, do you still lose
    > > > the +5? If you do, the diode is backwards or bad or miswired. (Or the
    > > > coil itself is bad). If you don't, take a look at the work on the
    > > > power supply board. Did it work before the power supply board was
    > > > modified? (I only do about 1/2 the mods Clay suggests for the stern
    > > > version of the power supply board, I don't think some of the back to
    > > > front work is necessary as the stern version has beefier traces vs.
    the
    > > > bally board)
    > > >
    > > > Do you have any other boards you can try in the machine, (Solenoid
    > > > driver/power board)?
    >
  6. Archived from groups: rec.games.pinball (More info?)

    No shorts that I could find on the board. I ran the mod grounding and
    +5V wires suggested on Marvin's site and everything else appeared
    alright. I unfortunately don't have another SDU board to swap in.
    I'll check the mounting brackets as well.

    - Sean
  7. Archived from groups: rec.games.pinball (More info?)

    Truly bizarre. Have you checked the back of the solenoid board for shorts
    to ground, other wires, or to the mounting brackets? Possibly swapped the
    board with another known-working one? That would quickly tell you if you
    should continue focusing on the solenoid board or look elsewhere....

    Weird!

    Ray J.
    --
    Action Pinball & Amusement, LLC
    Salt Lake City, Utah USA
    Web: www.actionpinball.com

    We're serious about pinball. Anything else is just for fun!


    "sean" <sspindler@ameritech.net> wrote in message
    news:1123188013.599918.57800@o13g2000cwo.googlegroups.com...
    > F3 on the power supply board is blowing - the one supplying the 12vdc
    > unregulated. I removed the header from the SDU that supplies the coil
    > pulldown from the transistors so they're not being energized at all.
    > If you can catch the start of the tread, there's some additional info
    > in there that may help pinpoint something more specific. Thanks Ray!
    >
    > - Sean
    >
  8. Archived from groups: rec.games.pinball (More info?)

    Double check that ground to the main filter capacitor. Make sure you didn't
    accidently go to the wrong lead.

    -- Ed

    "sean" <sspindler@ameritech.net> wrote in message
    news:1123191523.124150.13240@f14g2000cwb.googlegroups.com...
    > No shorts that I could find on the board. I ran the mod grounding and
    > +5V wires suggested on Marvin's site and everything else appeared
    > alright. I unfortunately don't have another SDU board to swap in.
    > I'll check the mounting brackets as well.
    >
    > - Sean
    >
  9. Archived from groups: rec.games.pinball (More info?)

    Figured it out! Went through all the boards with no luck, but found on
    the SDU that "Sol 18" had two pins - of which only ONE was supposed to
    be used. Found that on J3, pin9 was being used in the connector and
    labelled as N/U in the schematics!! Went through all the pins on this
    header, and moved it to pin13 as it should have been. Bingo! Machine
    works beautifully (well...except for the sound but that'll be another
    day).

    Thanks to all who replied. Today's lesson: check all connectors to
    make sure wires are in their right spots before replacing a bunch of
    chips!

    - Sean

    seymour-shabow@excite.com wrote:
    > Does it fire the solenoid/start to fire it before the fuse blows? So
    > it only blows the +5 fuse when it goes to fire the solenoid? Do you
    > have the diode on backwards, is the coil good? Also, what happens if
    > you ground the solenoid manually with a ground wire, do you still lose
    > the +5? If you do, the diode is backwards or bad or miswired. (Or the
    > coil itself is bad). If you don't, take a look at the work on the
    > power supply board. Did it work before the power supply board was
    > modified? (I only do about 1/2 the mods Clay suggests for the stern
    > version of the power supply board, I don't think some of the back to
    > front work is necessary as the stern version has beefier traces vs. the
    > bally board)
    >
    > Do you have any other boards you can try in the machine, (Solenoid
    > driver/power board)?
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