It boots right in to the settings menu and "automatically runs through them" at high speed - in advance mode as far as I can tell - and just keeps running through them over and over again WEIRD!!! It's like you have your finger on the "advance" switch and never let go...

1) Changed processor - no difference
2) Changed ram - no difference
3) Checked inputs/outputs at 7402 at 1F (Nor gates from the test switches on the door). Inputs are all high and outputs low as expected. Pin 8&9 High and Pin10 Low.... Pin 5&6 High and Pin4 Low (all correct)

4) Game Rom - I have burned 2x new ROM's 27256 using the code from IPDB but neither will boot the board? Just hangs and crashes on boot. This confuses me! as the original ROM boots in to this issue so I really wanted to change the Game Rom. I'm using M27C256B. They burn and verify but just won't boot the board?? I loaded the IPDB code in to the buffer and "verified" the original game rom and it verified ok. So the IPDB code looks right... baffled

HELP?

Also - I do not have a "laser war" so for testing I am just connecting power and displays on the CPU on one of my DE Machines to see the fault

#2 3 years ago

GTX

gdonovan

Pinside member

7y 185K 13,208 70

OP
Quoted from crazi:
I'm trying to help someone out with their Laser Wars CPU.
It boots right in to the settings menu and "automatically runs through them" at high speed - in advance mode as far as I can tell - and just keeps running through them over and over again WEIRD!!! It's like you have your finger on the "advance" switch and never let go...
1) Changed processor - no difference
2) Changed ram - no difference
3) Checked inputs/outputs at 7402 at 1F (Nor gates from the test switches on the door). Inputs are all high and outputs low as expected. Pin 8&9 High and Pin10 Low.... Pin 5&6 High and Pin4 Low (all correct)
4) Game Rom - I have burned 2x new ROM's 27256 using the code from IPDB but neither will boot the board? Just hangs and crashes on boot. This confuses me! as the original ROM boots in to this issue so I really wanted to change the Game Rom. I'm using M27C256B. They burn and verify but just won't boot the board??
HELP?

Check that the two connectors of the left side have not been swapped.
20200529_110009 (resized).jpg

#3 3 years ago

237

slochar

Pinside member

7y 86,550 6,882

OP
Quoted from crazi:
3) Checked inputs/outputs at 7402 at 1F (Nor gates from the test switches on the door). Inputs are all high and outputs low as expected. Pin 8&9 High and Pin10 Low.... Pin 5&6 High and Pin4 Low (all correct)

Next component up is a PIA.... any corrosion around any of these traces?

#4 3 years ago

DAD

crazi

Pinside member

Coatbridge

15y 41,400 307 8 6

Connectors are good...and still does it with the connectors off

No battery corrosion...

Are you meaning the Displays PIA? What bothers me though is that the displays are working fine...

#5 3 years ago

237

slochar

Pinside member

7y 86,550 6,882

No, the outputs of the chips you measured go directly to a PIA's. Since you have the correct information coming in/out of the 7402s, the next component in the chain is a PIA. Those 7402's aren't connected directly the microprocessor.

#6 3 years ago

DAD

crazi

Pinside member

Coatbridge

15y 41,400 307 8 6

Yes the outputs go directly to the Display PIA CA1 & CB1 and the displays are working fine

#7 3 years ago

DAD

crazi

Pinside member

Coatbridge

15y 41,400 307 8 6

Any reason why a M27C256B EPROM would not work on Laser Wars?

As mentioned I have burned and verified 2x and both won't boot the board. I really want to swap the Game Rom to see if it fixes this issue...

#8 3 years ago

DAD

crazi

Pinside member

Coatbridge

15y 41,400 307 8 6

Video of the issue

https://drive.google.com/open?id=17W1QT6gafIrlef0FMW83ueMKGLVHFDBJ

Boots right in to the settings then runs through them continuously

#9 3 years ago

237

slochar

Pinside member

7y 86,550 6,882

If I read the schematics correctly the outputs of those 7402 go into *inputs* of the PIA. The displays working don't factor into that - different port. It's just the next item up.

If you have chips verifying as good I doubt it's going to be the eprom although that is not unprecedented - I had a sound eprom on pinbot that verified all day on 2 different brands of burners and it was still bad.

#10 3 years ago

DAD

crazi

Pinside member

Coatbridge

15y 41,400 307 8 6

You reckon I should change the PIA?

It's just very strange that it won't boot on multiple new eproms - only the original. I have that voice telling me the fault could be a game code glitch. Wanted to factor that out first by swapping the eprom before starting to change other components on the board

#11 3 years ago

DAD

crazi

Pinside member

Coatbridge

15y 41,400 307 8 6

Replaced the Display PIA 11b - no difference

Not sure where to next other than trying to get another eprom to boot the board...

Thoughts???

#12 3 years ago

DAD

crazi

Pinside member

Coatbridge

15y 41,400 307 8 6

Took 2x known working (test roms I have for a different game) and wiped them clean. Burned Laser War code Ver: 1 on to both of them. Both of them won't boot the board either yet the original eprom boots the board....WTF???

#13 3 years ago

AMS

barakandl

nvram.weebly.com

12y 132K 10,414

It is probably not the EPROM.

Williams 3-6 games use a similar diag button input system with a 7402. If those games its possible to have a fault with that chip that makes the audits scroll constantly. In those games it is usually from the nearby battery holder rotting out the path to ground for the chip. If you have a logic probe or even DMM should be able to see activity thru the 7402 when the test buttons are pushed held down.

#14 3 years ago

DAD

crazi

Pinside member

Coatbridge

15y 41,400 307 8 6

Thanks Andrew - will take a look

Couldn't get new 27256 eproms to work. So installed J5 (removed J4) and copied the code to a 27512 and doubled up the code. That boots! (still got the exact same scrolling issue though)

At least I know in theory it's not the Game eprom. So moving on. Will just change the 7402 even though it seems to measuring fine but out of options now.

Still scratching my head why the 27256's wouldn't work...

#15 3 years ago

DAD

crazi

Pinside member

Coatbridge

15y 41,400 307 8 6

Replaced the 7402 but no difference

Burned a test IC from Marco on a 27512. It's flashing away. The Lamp PIA Pin2-17 are constant 3.8v whereas the other PIA's are fluctuation 0v - 5v - 0v (excluding the switch PIA which is correct).

Am I right in thinking that Lamp PIA 11D seems dodgy??? and would/could that cause the scrolling issue on settings after boot?

#16 3 years ago

DAD

crazi

Pinside member

Coatbridge

15y 41,400 307 8 6

Replaced the lamp PIA and it's now in attract mode!!! WOOHOO

#17 3 years ago

AMS

barakandl

nvram.weebly.com

12y 132K 10,414

OP
Quoted from crazi:
Replaced the lamp PIA and it's now in attract mode!!! WOOHOO

nice!

that PIA is probably the one that diag buttons go back too.

Reply

Wanna join the discussion? Please sign in to reply to this topic.

Hey there! Welcome to Pinside!

Donate to Pinside

Great to see you're enjoying Pinside! Did you know Pinside is able to run without any 3rd-party banners or ads, thanks to the support from our visitors? Please consider a donation to Pinside and get anext to your username to show for it! Or better yet, subscribe to Pinside+!

This page was printed from https://pinside.com/pinball/forum/topic/laser-wars-boots-in-to-settings-and-automatically-runs-through-them- and we tried optimising it for printing. Some page elements may have been deliberately hidden.

Scan the QR code on the left to jump to the URL this document was printed from.