WPC 89 Pop Bumpers Making my HEAD HURT !

[Guest]

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

I am being driven slowly mad by my BSD ! If the RGPers cannot aid me in
my struggle, I will be forced to call in an exorcist. Perhaps the
spirit of Vlad the Impaler can be forced out of my game.

Problem: Left and bottom pop bumpers do not fire IN GAME PLAY OR IN
SOLENOID or SWITCH TEST.

Symptoms: Center bumper fires normally,L & R bumpers will SCORE pts
or register in switch edges tests. LEft and bottom will fire if the TIP
102 is jumpered to ground. 67vdc at each coil lead, 11.50vdc at the PF
switches. If PF switch is jumpered, coils do NOT fire, switch registers
on test.

Actions taken so far:
Continuity good between J207 & J209 and PF coils & switches.

Continuity good J-pins and 1st resistor and diode on CPU board.

LEFT TIP 102 was fried,replaced along with 2N5401,1N4004 and 2
resistors, RIGHT not touched.

LS374 replaced and strip sockets installed. I double checked and buzzed
out every trace.Bottom bumper stopped working after this, worked weakly
before replacing LS374.

Continuity good from LS 374 to J113 ribbon connector.

Ribbon cable checked for continuity to CPU.

Continuity good from J209 up to LM339 on CPU brd.

Since things got worse after I replaced the LS374, it would appear
this is the problem, but I double checked and buzzed out every trace
from the LS374 and all the way to the TIP 102. This action MIGHT have
made the bottom bumper stop, but the left didn't work before or after.

Questions: Where do I go from here? If the 74LS240 was bad on the CPU
board, wouldn't that necessarily cause more problems downstream than
just the bumpers? Does this chip go bad ?

When the TIP 102 is jumpered to ground, this forces(emulates) the low
drop, grounding the TIP, verifying that the wiring to the coil is
functional, right?

Scoring or registering in the SWITCH EDGES test, should mean that
the PF to CPU brd wiring is functional, correct ?

Eternal gratitude and periodic offerings to Cthulu(sp?) shall be made
in the name of the RGPer would aids me in my battle with the beast.

 

[Guest]

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

You can try quickly grounding the ouput pin of the 74LS374 IC going to
the predriver and driver of one of your non working coils. Same idea as
your previous test of grounding the tab on the TIP102. By grounding the
pin, voltage on your base of the predriver should drop to below 5v
turning on the predriver, applying 5v to the diode, through the diode
and resistor to the base of the TIP102 turning it on, dropping the
collector tab to ground. Doing this test will at least devide the
problem up to see if it's a driver problem or LS374 area problem. Just
ground it for short durations, no damage will be done.

 

[Guest]

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

I would use your meter to watch the signals on the known working
bumper, then trace back your signals on the non-working bumper and
find out where the signals stop.

Bill; Just to clarify, do you mean before the TIP 102 or after ? Please
explain in detail. Game reset prob has been eliminated, dead short in
new coil was the culprit.

Ron; If the coil fires while grounding the LS374, would that indicate
a problem with the CPU board, namely the 74LS240 or LM 339 chips ?

Thanks to you both for the input.
Pinball Bob

 

[Guest]

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

On 25 Jul 2005 13:14:28 -0700, kul4skool1@hotmail.com wrote:

>I am being driven slowly mad by my BSD ! If the RGPers cannot aid me in
>my struggle, I will be forced to call in an exorcist. Perhaps the
>spirit of Vlad the Impaler can be forced out of my game.
>
> Problem: Left and bottom pop bumpers do not fire IN GAME PLAY OR IN
>SOLENOID or SWITCH TEST.
>
> Since things got worse after I replaced the LS374, it would appear
>this is the problem, but I double checked and buzzed out every trace
>from the LS374 and all the way to the TIP 102. This action MIGHT have
>made the bottom bumper stop, but the left didn't work before or after.

I would use your meter to watch the signals on the known working
bumper, then trace back your signals on the non-working bumper and
find out where the signals stop.

> When the TIP 102 is jumpered to ground, this forces(emulates) the low
>drop, grounding the TIP, verifying that the wiring to the coil is
>functional, right?

Yes. You mentioned in a previous post that doing this caused the game
to reset? Has that problem been solved?

> Scoring or registering in the SWITCH EDGES test, should mean that
>the PF to CPU brd wiring is functional, correct ?

It means your switches are working fine. For the moment, that's not
the issue. If your coils don't work in test mode, then your problem
lies with the Power Driver Board.

--
+-- Bill Ung --- <http://www.ufopinball.com/> ------------+
| HÍGH SPÉÉD: "Dispatch this is 504, suspect got away." |
| ÉÁRTHSHÁKÉR: "Ooohhh, bitchin!!" |
| WHÍTÉWÁTÉR: "Dang, lost another one!" |
| ÉLVÍRÁ: "Let's Boooogie!!! ..... Thank you, Boys!" |
+---------------------------------------------------------+

 

[Guest]

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

What Bill is saying is to do a test on a working solenoid, your working
bumper for example, get your meter out and watch the voltage swings
when the solenoid is activated. The voltage on the output pin of the
74LS374 will drop to ground when the solenoid is activated, at the same
time the output of the predriver will go high, through the diode and
resistor to the base of the TIP102. High on base of TIP102 causes
collector tab to drop to ground turning on your solenoid. You need a
decent meter that can read quick voltage swings because the drop only
happens for about 30us in test. A scope is even better because you can
accurately see the whole event. Now after seeing how a working solenoid
acts, move over to the output pin of the 74LS374 for a nonworking one
and read the voltage swings. See if the output pin acts just like the
working one. If so procede further into the predriver and check there,
if OK there on to the TIP102. Just basically see what is different and
where it changes to get you in the aera of problem. If no voltage swing
on the 74LS374 continue looking around that chip and be sure all 8
input pins have data on them with a scope or logic probe.
What I was saying is by quicky grounding the output pin of the 74LS374
if your solenoid activates you have proven that the predriver and
driver string is working so time to check around the 74LS374 further. I
don't think is possible the 74LS240 could cause this problem because
the data outputs on it feed multiple 74LS374s so a bad 240 would cause
multiple 74LS374s to not work.

kul4skool1@hotmail.com wrote:
> I would use your meter to watch the signals on the known working
> bumper, then trace back your signals on the non-working bumper and
> find out where the signals stop.
>
> Bill; Just to clarify, do you mean before the TIP 102 or after ? Please
> explain in detail. Game reset prob has been eliminated, dead short in
> new coil was the culprit.
>
> Ron; If the coil fires while grounding the LS374, would that indicate
> a problem with the CPU board, namely the 74LS240 or LM 339 chips ?
>
> Thanks to you both for the input.
> Pinball Bob

 

[Guest]

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

Ron;
Thanks for the clarification. Your reasoning sounds good, so I will
try that procedure. I am getting a logic probe in a couple of days, so
I will use that on the 74LS374.

A new, possibly related problem has arisen. The crypt popper has
stopped working. It did work previously before I replaced the LS374, I
am uncertain if it worked after that. The opto works (checked with a
digital camera) switch registers in the switch test, coil does not
fire. 69vdc to coil. The only common denominator ? Goes through J209,
so I replaced all the plug pins, no go. Where does it end up ? At U19
on the CPU, a 74LS240, same one as the 2 bumpers. The plot thickens...

I will try the other diagnostic procedures you guys suggested first.

Pinball Bob

 

[Guest]

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

Another quick question. Could a chip like the 74LS374 or 74LS240 fail
ONLY on some internal connections, say, C1 to D1, but not on the
others, C2 to D2, or does the entire chip fail internally at all pin
connections ?

 

[Guest]

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

yes, it is relatively common for a couple of circuits on an IC to fail
and have the rest of the chip continue to work. (More common than the
whole chip failing, unless some kind of overvoltage was involved which
usually involves all the circuits)

 

[Guest]

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

Ron, Bill or Seymour,

Update:
I shorted to ground the pins at 74LS374 and the pop bumpers work. Am
I correct in believing the problem must be upstream in the CPU board
or connectors from CPU to Pwr Drv brd ?

I tried to measure the voltage difference at the working pop bumper
at the LS374 chip output pin, but my meter only showed a steady 4.74v
as the bumper cycled. I imagine it's not sensitive enough to detect the
flucuations. I am getting a logic probe soon, so I'll re-do the test.

Can I eliminate the pathway via the J209 connector and associated
LM339 chip circuits at the CPU, as a source of trouble ? As unlikely as
it seems, the 74LS240 is beginning to appear as a good suspect.

Pinball Bob

 

[Guest]

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

At this point you've eliminated the predrivers and drivers as the
problem, and since the switches are recognised, the CPU seems to be
working. So the 74LS374 area seems to be bad. One more thing to check
is that none of the 8 input pins reads shorted to any of the other
input pins on the 74LS374. Small solder bridges shorting pins together
can cause unusual problems.
kul4skool1@hotmail.com wrote:
> Ron, Bill or Seymour,
>
> Update:
> I shorted to ground the pins at 74LS374 and the pop bumpers work. Am
> I correct in believing the problem must be upstream in the CPU board
> or connectors from CPU to Pwr Drv brd ?
>
> I tried to measure the voltage difference at the working pop bumper
> at the LS374 chip output pin, but my meter only showed a steady 4.74v
> as the bumper cycled. I imagine it's not sensitive enough to detect the
> flucuations. I am getting a logic probe soon, so I'll re-do the test.
>
> Can I eliminate the pathway via the J209 connector and associated
> LM339 chip circuits at the CPU, as a source of trouble ? As unlikely as
> it seems, the 74LS240 is beginning to appear as a good suspect.
>
> Pinball Bob

 

[Guest]

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

Ron & Bill or Seymour;

OK, checked pins on 74LS374 and NO continuity between adjacent pins. I
now believe I have 2 different problems.

Left bumper: 74LS374, input-HIGH pulse, output-pulse. Testing on Q54
TIP102 left leg- LOW pulse, right leg-LOW pulse Coil does NOT fire, but
will if grounded with a jumper. This sounds to me like a bad connection
between leg of TIP 102 and connector J127. Is that right ? What's going
on ?

Bottom bumper & crypt popper- 74LS374 input-high, output-NULL NO
pulsing- Is this a bad feed from 74LS240? broken trace or bad chip ?
Jumper to ground fires bottom pop, did not try crypt because it is a
TIP36c. Can I ground the driver TIP102 for the TIP36c to fire the coil
?

I'm learning stuff everyday, it's just that it's making my brain
hurt !

Pinball Bob

 

[Guest]

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

OK, I think you're narrowing things down. The right leg of the TIP102
should be grounded, so on the one you're getting pulsing on both the
right and left legs it sounds like your ground is bad. Get your ohmeter
out and read the resistance from ground to the right leg. It should be
zero. If not invesigate the board to find why it is not.
If you're missing the pulsing on any input legs to the 74LS374, note
which legs are missing pulses then check the same pins on another
74LS374 in the game. All the 8 data lines go to all the 74LS374 IC
chips so in other words if other 74LS374 IC chips have pulsing on these
pins, this essentially eliminates the 74LS240 as the problem. In this
case follow the circuitry from the missing pulse pins to find where the
open circuit is between them and the other 74LS374s. It sounds like
open board on all accounts to me.

kul4skool1@hotmail.com wrote:
> Ron & Bill or Seymour;
>
> OK, checked pins on 74LS374 and NO continuity between adjacent pins. I
> now believe I have 2 different problems.
>
> Left bumper: 74LS374, input-HIGH pulse, output-pulse. Testing on Q54
> TIP102 left leg- LOW pulse, right leg-LOW pulse Coil does NOT fire, but
> will if grounded with a jumper. This sounds to me like a bad connection
> between leg of TIP 102 and connector J127. Is that right ? What's going
> on ?
>
> Bottom bumper & crypt popper- 74LS374 input-high, output-NULL NO
> pulsing- Is this a bad feed from 74LS240? broken trace or bad chip ?
> Jumper to ground fires bottom pop, did not try crypt because it is a
> TIP36c. Can I ground the driver TIP102 for the TIP36c to fire the coil
> ?
>
> I'm learning stuff everyday, it's just that it's making my brain
> hurt !
>
> Pinball Bob

 

[Guest]

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

SUCCESS ! Thanks to your advice Ron, I saw that the TIP102 right
leg had a lifted trace above it, keeping it from grounding. I soldered
a jumper wire from that leg to the ground plain on the solder side of
the board. Is this a reasonable way to fix this? The trace was burnt up
and tight in their, so I didn't try to repair it on the component side.
Also, I don't really know what I am doing.

There was NO continuity between pin 4 on the 74LS374 before the
replaced one and the new one, so it broke the train to the following
chip causing the crypt popper to fail. I soldered another jumper wire
solder side, to each pin and...

Voila, she works !!!!

Thanks very much to all who contributed their ideas & helped me. The
RGP is a great asset to anyone in this hobby.

Pinball Bob

 

[Guest]

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

Great job. Very nice to hear the results and that it's fixed.
Ron

kul4skool1@hotmail.com wrote:
> SUCCESS ! Thanks to your advice Ron, I saw that the TIP102 right
> leg had a lifted trace above it, keeping it from grounding. I soldered
> a jumper wire from that leg to the ground plain on the solder side of
> the board. Is this a reasonable way to fix this? The trace was burnt up
> and tight in their, so I didn't try to repair it on the component side.
> Also, I don't really know what I am doing.
>
> There was NO continuity between pin 4 on the 74LS374 before the
> replaced one and the new one, so it broke the train to the following
> chip causing the crypt popper to fail. I soldered another jumper wire
> solder side, to each pin and...
>
> Voila, she works !!!!
>
> Thanks very much to all who contributed their ideas & helped me. The
> RGP is a great asset to anyone in this hobby.
>
> Pinball Bob