(Topic ID: 99236)

Early Bally, can't get 4th flash from the MPU. U10 chip and socket replaced.

By mg81

9 years ago


Topic Heartbeat

Topic Stats

You

Linked Games

#1 9 years ago

The early Bally solid state pins are the ones I have collected the most over the years and I normally feel pretty confident in fixing them, but I could really use some more input on this one.

The pin is Flash Gordon and the MPU looks great, NO battery leak damage, none!!! This might be the only Bally I have owned that does not have any damage. It would figure that this would be the board that gives me the most trouble. Some of my other Bally's MPUs look awful and work just fine.

The problem:
-I can only get 3 flashes after the initial "flicker". So that should me the U10 chip or socket is bad.
-Thankfully I have plenty of working Bally pins to steal parts from and use as test fixtures.
-I have put in a known working U10 chip, No forth flash.
-I put installed a nice set of machine socket strips to replace the old socket. No 4th flash
-I put a Ohm meter on every chip leg on the working U10 chip and the other probe onto the solder pad of the new socket on the board. No resistance, all solder connections are good.
-Known good power supply.
-I don't see any damaged traces, this board looks great. (Though I have not "buzzed out" all of the traces on the board to check them all.)

What are my options?
-The only thing I see left is my old Clay's manual says the U20 chip. Sadly this chip is not socketed, so I can't easily steal one from a working machine and I don't have any spares.

Anyone have any other recommendations on what to do other than a parts order for a U20 chip?

#2 9 years ago

Check the solenoid fuse on the bottom of the playfield. I'm not sure if it's the fourth flash or not, but that will stop the MPU from booting.

#3 9 years ago

Um, no, the playfield coil fuse has nothing to do with the MPU booting. The solenoid power fuse will stop the last LED blink.

Swap U9.

If same, check for shorts to ground on U10 pins 2-9. This could be solder bridge or shorted cap.

If OK, the manual suggests using the AID2 test rig to check continuity for U10 pins 21-24, 26-33, 35 and 36. So you could beep those out to their respective destinations.

If U17 is socketed you might try that.

There's more in the F.O. manual but it looks like you have to use the AID2 rig.

#4 9 years ago
Quoted from cody_chunn:

The solenoid power fuse will stop the last LED blink.

I think that's what he meant.

#6 9 years ago

U9 chip was replaced with a known working chip.

I will check out the other items listed by cody_chunn and see what I get.

But everyone feel free to keep posting other possible ideas.

Thanks

5 years later
#7 4 years ago
Quoted from mg81:

U9 chip was replaced with a known working chip.
I will check out the other items listed by cody_chunn and see what I get.
But everyone feel free to keep posting other possible ideas.
Thanks

mg81 did you ever get this resolved? I am in the same place on my Eight Ball. No 4rth flash and did all the same things in your first post.

#8 4 years ago
Quoted from slghokie:

I am in the same place on my Eight Ball. No 4rth flash and did all the same things in your first post.

See post #3 by @cody_chunn with respect to a short on pins 2 to 9 of U10. With the machine off, measure the resistance on each of those pins with respect to ground on the MPU board. You should get the same resistance reading on all those pins. An external short on one of those pins will manifest as a U10 failure and cause no 4th LED flash on boot-up.

5 months later
#9 4 years ago

I have a similar problem.
Socket repaced, pia chip tested and found to be oke.
All traces verified.
No short on the address lines (2 thru 9) or any other pins.
Replaced U20, no help.
I'm scratching my head because I don't know what I've done wroung...

#10 4 years ago
Quoted from Inkochnito:

No short on the address lines (2 thru 9) or any other pins.

What resistance with respect to ground do you measure on each of these I/O pins 2 through 9?
Did you measure for shorts directly between these I/O pins 2 through 9?

#11 4 years ago
Quoted from Quench:

What resistance with respect to ground do you measure on each of these I/O pins 2 through 9?
Did you measure for shorts directly between these I/O pins 2 through 9?

Between ground and the I/O pins 2K8 each.
Between pins 3K9.

#12 4 years ago

There is a trace coming from the zero cross detector that passes along tight spaced to one of the PIAs solder pad row... i think its U10. More than once have I seen a PIA leg short to that trace and make the power on self test fail.

#13 4 years ago
Quoted from Inkochnito:

I have a similar problem.

What's the history of this board? Did it suddenly fail or did you receive it with this problem to fix?
How about battery corrosion?

Have you confirmed data, address, R/W, E and CS (chip select) activity to the U10 chip?

#14 4 years ago
Quoted from Quench:

What's the history of this board? Did it suddenly fail or did you receive it with this problem to fix?
How about battery corrosion?
Have you confirmed data, address, R/W, E and CS (chip select) activity to the U10 chip?

The history is unknown.
PIA's and rams checked with the Neoloch.
Battery corrosion is fixed by me.
The via's under U11 (in the corrosion zone) have a wire through now and all is clear and clean.
Is there a simple way (like the address lines) to check the data lines other than a scoop?
I do have a Picoscoop to connect to my computer.
I haven't set it up right now, but can do this next weekend.

#15 4 years ago
Quoted from Inkochnito:

Is there a simple way (like the address lines) to check the data lines other than a scoop?

Logic probe on each line d0-d7 just looking for activity would work. I doubt there's anything wrong with the data lines themselves because you wouldn't get as far as you do into the bootup if there were. (if they were shorted)

I think you're looking for activity on the suspect chips to make sure some data is getting there. Now, if it's the CORRECT data or not, would require a logic analyzer or a storage scope with enough lines to capture all of it.

#16 4 years ago

What slochar said.
A logic probe for starters just looking for activity on the signals I mentioned is what to check for. You need to power off and back on to check for activity on each signal because once the PIA test has failed the boot test, some of those signals will no longer change state until you reboot.

BTW do us a favor and post some clear pictures of the board.

#17 4 years ago
Quoted from barakandl:

More than once have I seen a PIA leg short to that trace and make the power on self test fail.

Well, this was the problem with my board....
The was a short between a data line going between address lines under the U10 socket.
Nearly impossible to see, just a little tin drop in the resin.
The board works perfectly now.

#19 4 years ago

I must ask - what kind of socket did you use?

#20 4 years ago
Quoted from oldschoolbob:

I must ask - what kind of socket did you use?

Single strips. Cut to size.

#21 4 years ago

Thanks Inkochnito, I've had problems before with those machined sockets - They seem to be prone to shorting to traces between pins. Never had that problem with twin leaf sockets.

Promoted items from Pinside Marketplace and Pinside Shops!
$ 7.00
Playfield - Decals
Pinball Haus
 
$ 8.00
Electronics
Third Coast Pinball
 
Wanted
Machine - Wanted
South Milwaukee, WI
$ 30.00
Lighting - Led
Pinballrom
 
$ 22.50
From: £ 135.00
Electronics
Retro Electro Designs
 
$ 179.00
$ 90.00
$ 99.00
$ 29.00
Boards
RoyGBev Pinball
 
$ 125.00
Electronics
Pinball Haus
 
From: £ 110.00
From: $ 130.00
Boards
Troxel Repair
 
$ 22.95
Eproms
Pinballrom
 
$ 69.00
Gameroom - Decorations
Pinball Pimp
 
From: £ 135.00
Electronics
Retro Electro Designs
 
$ 18.95
Eproms
Pinballrom
 
$ 29.00
Boards
RoyGBev Pinball
 
$ 10.00
Wanted
Machine - Wanted
Berkeley Springs, WV
Great pinball charity
Pinball Edu

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 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.