Discussion:
Tech: Game Plan CPU
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g***@yahoo.com
2022-03-02 12:01:34 UTC
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Flashes 4 times then stops. I have changed U17 and U4 as the repair guide states. I have tested continuity from all pins, I also went backward to U5 and changed that. Still, only 4 flashes. Any suggestions are appreciated.
John Robertson
2022-03-02 15:05:33 UTC
Permalink
Post by g***@yahoo.com
Flashes 4 times then stops. I have changed U17 and U4 as the repair guide states. I have tested continuity from all pins, I also went backward to U5 and changed that. Still, only 4 flashes. Any suggestions are appreciated.
You need a Logic Probe or Oscilloscope at this point.

Check inputs to U14 - pins 20 through 23 - they should all be pulsing.

If good then check U14 outputs pins 14 - 17 inclusive, again they should
be pulsing.

If bad, check U17 pins 37 through 40 inclusive, are they all pulsing? If
yes, then there is a connection problem between U17 and U14 pins. If no,
then do a continuity check to ground or Vcc on those four pins - any
shorted to ground or Vcc?

I have a Game Plan pinball support page (added the above to) here:

https://flippers.com/gameplanTips.html

John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
g***@yahoo.com
2022-03-03 11:35:25 UTC
Permalink
Post by John Robertson
Post by g***@yahoo.com
Flashes 4 times then stops. I have changed U17 and U4 as the repair guide states. I have tested continuity from all pins, I also went backward to U5 and changed that. Still, only 4 flashes. Any suggestions are appreciated.
You need a Logic Probe or Oscilloscope at this point.
Check inputs to U14 - pins 20 through 23 - they should all be pulsing.
If good then check U14 outputs pins 14 - 17 inclusive, again they should
be pulsing.
If bad, check U17 pins 37 through 40 inclusive, are they all pulsing? If
yes, then there is a connection problem between U17 and U14 pins. If no,
then do a continuity check to ground or Vcc on those four pins - any
shorted to ground or Vcc?
https://flippers.com/gameplanTips.html
John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
Hello John, Thank you for the suggestions.
Here is where I am at as of 11pm last night.
Everything you mentioned is good except, U14 pin 2 is being pulled to ground.
This does not happen on a known good board.
U14 pin 2 goes to U19 pin 12 and then to U21 pin 1.
At that point I went to bed.
I have to work on a car this morning and later I will get back to this.

Regards
George
g***@yahoo.com
2022-03-04 00:11:12 UTC
Permalink
Post by g***@yahoo.com
Post by John Robertson
Post by g***@yahoo.com
Flashes 4 times then stops. I have changed U17 and U4 as the repair guide states. I have tested continuity from all pins, I also went backward to U5 and changed that. Still, only 4 flashes. Any suggestions are appreciated.
You need a Logic Probe or Oscilloscope at this point.
Check inputs to U14 - pins 20 through 23 - they should all be pulsing.
If good then check U14 outputs pins 14 - 17 inclusive, again they should
be pulsing.
If bad, check U17 pins 37 through 40 inclusive, are they all pulsing? If
yes, then there is a connection problem between U17 and U14 pins. If no,
then do a continuity check to ground or Vcc on those four pins - any
shorted to ground or Vcc?
https://flippers.com/gameplanTips.html
John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
Hello John, Thank you for the suggestions.
Here is where I am at as of 11pm last night.
Everything you mentioned is good except, U14 pin 2 is being pulled to ground.
This does not happen on a known good board.
U14 pin 2 goes to U19 pin 12 and then to U21 pin 1.
At that point I went to bed.
I have to work on a car this morning and later I will get back to this.
Regards
George
7pm update.
U21 was bad which was causing pin 2 of U14 to go to ground.
Replaced it with a new 74LS379.
Still 4 flashes, but now the displays show a number 7 in all 5 displays.
John Robertson
2022-03-11 18:03:07 UTC
Permalink
Post by g***@yahoo.com
Post by g***@yahoo.com
Post by John Robertson
Post by g***@yahoo.com
Flashes 4 times then stops. I have changed U17 and U4 as the repair guide states. I have tested continuity from all pins, I also went backward to U5 and changed that. Still, only 4 flashes. Any suggestions are appreciated.
You need a Logic Probe or Oscilloscope at this point.
Check inputs to U14 - pins 20 through 23 - they should all be pulsing.
If good then check U14 outputs pins 14 - 17 inclusive, again they should
be pulsing.
If bad, check U17 pins 37 through 40 inclusive, are they all pulsing? If
yes, then there is a connection problem between U17 and U14 pins. If no,
then do a continuity check to ground or Vcc on those four pins - any
shorted to ground or Vcc?
https://flippers.com/gameplanTips.html
John :-#)#
--
Hello John, Thank you for the suggestions.
Here is where I am at as of 11pm last night.
Everything you mentioned is good except, U14 pin 2 is being pulled to ground.
This does not happen on a known good board.
U14 pin 2 goes to U19 pin 12 and then to U21 pin 1.
At that point I went to bed.
I have to work on a car this morning and later I will get back to this.
Regards
George
7pm update.
U21 was bad which was causing pin 2 of U14 to go to ground.
Replaced it with a new 74LS379.
Still 4 flashes, but now the displays show a number 7 in all 5 displays.
Hi George,

That is odd, normally displays do not come alive until the last flash.

Was there any corrosion on the motherboard? I'd be checking for traces
that have given up.

John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
g***@yahoo.com
2022-03-12 12:01:43 UTC
Permalink
Post by John Robertson
Post by g***@yahoo.com
Post by g***@yahoo.com
Post by John Robertson
Post by g***@yahoo.com
Flashes 4 times then stops. I have changed U17 and U4 as the repair guide states. I have tested continuity from all pins, I also went backward to U5 and changed that. Still, only 4 flashes. Any suggestions are appreciated.
You need a Logic Probe or Oscilloscope at this point.
Check inputs to U14 - pins 20 through 23 - they should all be pulsing.
If good then check U14 outputs pins 14 - 17 inclusive, again they should
be pulsing.
If bad, check U17 pins 37 through 40 inclusive, are they all pulsing? If
yes, then there is a connection problem between U17 and U14 pins. If no,
then do a continuity check to ground or Vcc on those four pins - any
shorted to ground or Vcc?
https://flippers.com/gameplanTips.html
John :-#)#
--
Hello John, Thank you for the suggestions.
Here is where I am at as of 11pm last night.
Everything you mentioned is good except, U14 pin 2 is being pulled to ground.
This does not happen on a known good board.
U14 pin 2 goes to U19 pin 12 and then to U21 pin 1.
At that point I went to bed.
I have to work on a car this morning and later I will get back to this.
Regards
George
7pm update.
U21 was bad which was causing pin 2 of U14 to go to ground.
Replaced it with a new 74LS379.
Still 4 flashes, but now the displays show a number 7 in all 5 displays.
Hi George,
That is odd, normally displays do not come alive until the last flash.
Was there any corrosion on the motherboard? I'd be checking for traces
that have given up.
John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
No corrosion at all, that is what bothers me.
Continuity, good everywhere I check.
One number 7 comes up in all displays.
Flashes 4 times then stops every time.
g***@yahoo.com
2022-03-19 11:17:49 UTC
Permalink
Post by g***@yahoo.com
Post by John Robertson
Post by g***@yahoo.com
Post by g***@yahoo.com
Post by John Robertson
Post by g***@yahoo.com
Flashes 4 times then stops. I have changed U17 and U4 as the repair guide states. I have tested continuity from all pins, I also went backward to U5 and changed that. Still, only 4 flashes. Any suggestions are appreciated.
You need a Logic Probe or Oscilloscope at this point.
Check inputs to U14 - pins 20 through 23 - they should all be pulsing.
If good then check U14 outputs pins 14 - 17 inclusive, again they should
be pulsing.
If bad, check U17 pins 37 through 40 inclusive, are they all pulsing? If
yes, then there is a connection problem between U17 and U14 pins. If no,
then do a continuity check to ground or Vcc on those four pins - any
shorted to ground or Vcc?
https://flippers.com/gameplanTips.html
John :-#)#
--
Hello John, Thank you for the suggestions.
Here is where I am at as of 11pm last night.
Everything you mentioned is good except, U14 pin 2 is being pulled to ground.
This does not happen on a known good board.
U14 pin 2 goes to U19 pin 12 and then to U21 pin 1.
At that point I went to bed.
I have to work on a car this morning and later I will get back to this.
Regards
George
7pm update.
U21 was bad which was causing pin 2 of U14 to go to ground.
Replaced it with a new 74LS379.
Still 4 flashes, but now the displays show a number 7 in all 5 displays.
Hi George,
That is odd, normally displays do not come alive until the last flash.
Was there any corrosion on the motherboard? I'd be checking for traces
that have given up.
John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
No corrosion at all, that is what bothers me.
Continuity, good everywhere I check.
One number 7 comes up in all displays.
Flashes 4 times then stops every time.
A bad 7417
John Robertson
2022-03-19 21:38:51 UTC
Permalink
Post by g***@yahoo.com
Post by g***@yahoo.com
Post by John Robertson
Post by g***@yahoo.com
Post by g***@yahoo.com
Post by John Robertson
Post by g***@yahoo.com
Flashes 4 times then stops. I have changed U17 and U4 as the repair guide states. I have tested continuity from all pins, I also went backward to U5 and changed that. Still, only 4 flashes. Any suggestions are appreciated.
You need a Logic Probe or Oscilloscope at this point.
Check inputs to U14 - pins 20 through 23 - they should all be pulsing.
If good then check U14 outputs pins 14 - 17 inclusive, again they should
be pulsing.
If bad, check U17 pins 37 through 40 inclusive, are they all pulsing? If
yes, then there is a connection problem between U17 and U14 pins. If no,
then do a continuity check to ground or Vcc on those four pins - any
shorted to ground or Vcc?
https://flippers.com/gameplanTips.html
John :-#)#
--
Hello John, Thank you for the suggestions.
Here is where I am at as of 11pm last night.
Everything you mentioned is good except, U14 pin 2 is being pulled to ground.
This does not happen on a known good board.
U14 pin 2 goes to U19 pin 12 and then to U21 pin 1.
At that point I went to bed.
I have to work on a car this morning and later I will get back to this.
Regards
George
7pm update.
U21 was bad which was causing pin 2 of U14 to go to ground.
Replaced it with a new 74LS379.
Still 4 flashes, but now the displays show a number 7 in all 5 displays.
Hi George,
That is odd, normally displays do not come alive until the last flash.
Was there any corrosion on the motherboard? I'd be checking for traces
that have given up.
John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
No corrosion at all, that is what bothers me.
Continuity, good everywhere I check.
One number 7 comes up in all displays.
Flashes 4 times then stops every time.
A bad 7417
Hi George,

Is that what you found? Which 7417 (if there is more than one that is...)

Sorry, I got busy and forgot to follow up...

John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
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