Re: TZ Ground Short Issue

On Mar 5, 11:52 am, "Tony @ GLM" <cl...@xxxxxxxxxxxxxxxxxxxxx> wrote:
On Mar 5, 1:04 pm, Metahugh <metah...@xxxxxxxxx> wrote:





On Mar 5, 2:20 am, "Tony @ GLM" <cl...@xxxxxxxxxxxxxxxxxxxxx> wrote:

On Mar 5, 12:21 am, Metahugh <metah...@xxxxxxxxx> wrote:

On Mar 5, 12:06 am, Taylor-VA <TaylorV...@xxxxxxxxx> wrote:

On Mar 4, 11:57 pm, "Tony @ GLM" <cl...@xxxxxxxxxxxxxxxxxxxxx> wrote:

On Mar 4, 11:14 pm, Metahugh <metah...@xxxxxxxxx> wrote:

On Mar 4, 7:54 pm, Metahugh <metah...@xxxxxxxxx> wrote:

On Mar 4, 7:25 pm, RonKZ...@xxxxxxx wrote:

On Mar 4, 5:14 pm, Metahugh <metah...@xxxxxxxxx> wrote:

On Mar 4, 5:27 pm, "Tony @ GLM" <cl...@xxxxxxxxxxxxxxxxxxxxx> wrote:

On Mar 4, 5:20 pm, Taylor-VA <TaylorV...@xxxxxxxxx> wrote:

You need to isolate the problem. I would unplug anything associated
with u20 and then plug stuff in until it blows.

The better way to deal with this is to unplug J206/207 and J212 and do
a continuity check on EACH wire against all of the power supply
voltages (+12V, +50V, etc) until the problem column line(s) are found
and you determine which voltage rail it's shorted to.  Then follow
that column wire back through the game until you uncover the source of
the short.

Tonywww.greatlakesmodular.com-Re-EngineeredPinballParts!

So if I understand properly I should unplug those connectors and check
each wire to see if I see voltages being displayed.  Depending on
whether or not it's +12v or +50v that will tell me generally where the
issue lies?  Like it could be either GI voltage or coil voltage that
is being shorted to it?

Should I measure the voltage on each wire against the cab ground
(ground braid)?  I still have to find out why my pin 1 on the opto
board is connected to the cabinet ground.  My other opto board is
unusable right now and of course I don't want to plug in my new board
and fry it :)

Hugh

I can't help, but will mention J5 pin 1 is ground. So continuity to
ground braid is normal.

Yeah I read the instructions wrong... DOH!  It says:

"With a continuity meter (DMM), test for continuity (shorting) from
the game's ground braid (located on both sides of the cabinet) to the
ground pin of J5 (pin1) wiring harness.  There should be NO continuity
from between the ground braid and the 10 opto board!"

The last two words of the first sentence, wiring harness, threw me off
(it's pretty easy lemme tell ya LOL).   I tested from pin 1 on the
harness itself to the ground braid and of course there was continuity.

I do NOT have continuity from pin 1 of J5 with the harness
disconnected.  I guess some have hacked wires to other connectors on
the opto board to ground and the only connection to ground to the main
cab should be on pin 1 of J5.

Okey dokie, now to put the kids to sleep and hopefully not fall asleep
myself so I can work on this some more :)

Hugh

Of course that should have ground.  I was thinking that J5 pin 1 was
ground to just the opto switches but no, that's the ground to the
game.

Hugh

Well i've found an interesting problem.  I installed my new opto board
and I was testing it.  I noticed that with the playfield up the center
metal ramp's opto pair wouldn't register.  I lowered it to continue
testing and I rested my arm on the siderail and put my finger between
the opto pair to see if it registered.  I touched something and WOW a
huge shock.  I'm thinking what in the world did I touch...  so stupid
me recreates the scenario and gets shocked again :)

Turns out that the center ramp is electrified!  With the game on I
touched my negative DMM lead to the siderail and the other to the
ramp.  72.1 volts!  I turned the game off immediately and started
looking for a short somewhere around that ramp.  I put the playfield
down and touched it again, and it is still electrified!  I completely
removed the game from power.  In a moment of humor I pulled out my
Fluke 80k/40 I use to discharge monitors to discharge the game :)

Somehow it seems the driver board is feeding electricity through the
entire game.  What should I check next?

Hugh

Ack!  70V is coil power.   Check the bridge diverter coil as that's
would be the one that's directly connected via metal to the center
ramp.

Tonywww.greatlakesmodular.com-Re-EngineeredPinballParts!

Hugh, in that thread you sent me earlier someone had mentioned a screw
coming loose on the diverter and shorting out U20(i think).
Coincidence?

I was thinking about that actually.  It's a metal t-nut installed in
the top of the playfield to help mount the diverter.  Whoever did this
mod should be shot!!  If somehow coil power was shorted to that I
could have been sending voltage anywhere on my playfield.  I plan on
getting the playfield restored and that mod reversed but I had hoped
to play the game a bit first.  Oh well :(

Hugh

Here's something from an old post you might want to check out:

"As Clive may remember, I had a similar problem and traced the short
to
the coil on the ramp bridge diverter. The coil was mounted upsidedown
causing one of the coil terminals to contact the bridge diverter
mount.
This charged the entire right ramp with coil voltage. The center clock
target would contact the ramp when hit hard and cause the 2803 to blow
the respective column causing all the corresponding switches to not
function.  Therefore check the mounts of all the coils."

Cheers,

Tonywww.greatlakesmodular.com-Re-EngineeredPinball Parts!

Thanks, I did look at this and I can't find a short on the diverter
but I can see how the power I am reading in my ramp could fry stuff.

You know what is super weird is after removing the driver board if I
check the power on the ramp I am getting minute readings with my DMM
in both AC and DC.  Since my driver board is removed I would suspect
to find only AC.  Hopefully I can tear into this some more tonight and
figure out what is going on.

Hugh

Minute amounts of voltage don't necessarily mean a whole lot.  You
could be getting that from any number of places and unless you
completely unplug the entire playfield from everything in the backbox,
I wouldn't worry about that so much as the 70V that's obviously going
somewhere it shouldn't.

I still suspect the diverter coil is the problem.  It could be
something you can't see such as a bad coil sleeve.  In any case, I
would disconnect the coil (unsolder the two wires) and re-test it.  If
that removes the 70V, then you've found the problem.  If not, then I'd
start looking at the clock target switch, which is about the only
other active electrical thing in proximity to the center metal ramp.
Most everything else is isolated from the metal either via wood or
plastic (such as the optos).

If it's the clock millions switch/column line, then start looking for
problems at the upper left flipper.  Most of the switches on that
column are tied to that side of the playfield (most being on the power
playfield).

Tonywww.greatlakesmodular.com- Re-Engineered Pinball Parts!- Hide quoted text -

- Show quoted text -

Also a high impedance meter, which is what basically all meters are,
may measure "ghost voltage". What this is that you measure voltage
that really isn't there due to no load. Some new meters have a low Z
setting for measuring presence of anwanted volts. The new Fluke 289
meter has a 3K ohm low impedance setting for checking power. You could
basically duplicate this feature by running a 3k ohm resistor from
ground to your ramp that has the volts you are measuring. Hook up all
your plugs and recheck volts from ground to the ramp. If volts are now
zero, you've been fooled by the ghosts. If volts are still 74 you've
got a major short to the ramp. It's not on the power board, or AC
power supply, lack of third prong, or anything else. It's a short
right on the ramp.
.

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