Bally MPU .. I only get 4 flashes, cycles 3 times and then..

[Guest]

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

This mpu had some acid damage. It's only flashed twice when I first got
it. Then I fixed the acid damage and replaced the hacked socket job on
the 5101 and got 3 flashes. Well I noticed the j4 connector was shot so
I replaced it and the header now I get 4 flashes, usualy cycles three
times with the flicker and 4 flashes then the led stays on. I replaced
the cpu socket and the u11 socket. I'll probably just replace the rest
of the sockets being used for good measure but I have a feeling it will
not make a difference. I am sure the cpu is working and pretty sure the
pia chips are good, and the ram chip as well. Anyone run into this?
I'll keep hacking on it but if there is something obvious I should look
at please let me know. I know I am getting very close.
Thanks!
~eric

 

[Guest]

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

Sounds like the reset circuit is damaged, or the +5V is not stable DC
(filter cap might be bad... on the solenoid/power drive board)

Don't go replacing connectors until you get the power stable. You can
measure with the meter on AC across the filer cap, if it's over a volt
or so you should replace it

 

[Guest]

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

after it does its cycle, try and short pins 39 and 40 on the 6821 u9..
see if it trys to boot. Also check the solder through points around u11
and also around the reset section. Could also try a new 6821 at u11.

 

[Guest]

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

Well u9 is the cpu and it does reset when these pins are shorted so I
guess it's the reset circuit. I don't know what it could be though
because most of the suspects have been replaced. I didn't replace vr1
yet though. I also think the sockets are pretty cheesy so I am going to
replace all the rom sockets just for good measure. already did the pia
sockets and the cpu. I had to replace the power connector becasue it
was falling apart. The board is getting correct voltages at the test
points. I guess I'll measure some voltages on the cpu and pia as
marvin's site suggests.
~eric

 

[Guest]

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

Eric I think I should have thought better on my last reply, if the led
is locked on and you short pins 39 and 40, and it then boots 100% (all
flashes) its the timer circuit (U15 and U16 If I remember correctly)
or the reset not syncing correctly with the 5v supply. I think your
reset circuit may actually be functioning properly. No 5th flash
usually means U11 or its socket is bad. I would definately replace the
socket at u11. Also pay very special attention to the solder through
holes around u11. Some of them are close to the bottom and are almost
always damaged from battery leakage. A good trick is to remove all the
solder from the through holes, gently sand and clean them (acetone and
a cue tip), place a piece of wire wrap through the hole (w/o insulation
of course) AND solder both sides. Looks a little hacky but it works and
wont be a connection that is affected by flexing. 90% of the MPU's I
fix (after rebuilding the reset section) are cause of through holes!

 

[Guest]

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

Problem solved!

I decided since I pretty much did everything to check my work on the
cmos area restoration. I checked it against my EBD mpu and found two
solder joints missing. The one that caused the false reporting of u11
being bad was between pins 12 and 13 on the cmos chip. So just
soldering those two together and the machine now boots up and plays but
I have display issues of course so I'll get to those. BTW This is an
Evel Knievel I picked up recently I had to replace one ic on the driver
board two tip102s two 330ohm resitors and the diodes next to them that
were cooked to all hell. Also replaced three burnt coils. It plays fine
now. Just need some minor work getting all the displays going. Well
I hope this helps someone, Iwas really spinning on it for a while.
thanks!
~eric

 

[Scott]

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

Are you referring to U8 as the CMOS chip (5101)?

Shouldn't it be Pins 9 & 10 soldered together AND Pins 13 & 14 AND
Pins 15 & 16?

I'm looking at one right now - getting ready to replace it and that's
how this board is setup (with original socket and solder).

Let me know.

Thanks

 

[Guest]

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

scott you are right, I just looked at one of my boards here. Those are
the ones connected together. I beleive eric was referring to the solder
through holes near the pins he described. I told ya Eric 90% of the
boards I repair are cause of solder through holes! especially when they
are near the battery, dont trust a damn one of them!

 

[Guest]

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

Oh yeah, that was my mista ke, 13 and 14 I also missed 9 and 10
junction but that had no effect 13 and 14 solved the problem, I should
have just looked at my other bally board when I was repairing the 5101
section and socket but I didn't bother. Well it's got all new sockets
and it needed it anyway. I'll be checking my work more often then
not.
Thanks everyone!!!
~eric