(Topic ID: 258717)

AS-2518-35 Continuously Rebooting


By JethroP

3 months ago



Topic Stats

  • 48 posts
  • 8 Pinsiders participating
  • Latest reply 85 days ago by JethroP
  • Topic is favorited by 1 Pinsider

You

Linked Games

Topic Gallery

There have been 32 images uploaded to this topic. (View topic image gallery).

Resistance Readings Rev 1.pdf (PDF preview)
Resistance Readings.pdf (PDF preview)
IMG_2911.JPG
IMG_2910.JPG
IMG_2909.JPG
MPU_U11_Socket_PinsA.jpg
IMG_2892.jpeg
IMG_2896.jpeg
IMG_2905.jpeg
IMG_2900.jpeg
IMG_2888.jpeg
IMG_2906.jpeg
MPU_Sockets 004a.jpg
IMG_2883.JPG
IMG_2882.JPG
IMG_2878.JPG

#1 3 months ago

LED flickers, then 1 flash, pause, then 6 more flashes. But then the sequence starts all over again but without the flicker. So it's like:
LED flickers, then 1 flash, pause, then 6 more flashes, then
1 flash, pause, then 6 more flashes, then
1 flash, pause, then 6 more flashes, then
1 flash, pause, then 6 more flashes, then
...etc.....

I took the MPU out and on the bench I get the 6 flashes. Then I temporarily short top of R17 and top of R23 and get the 7th flash, then the sequence starts over again.

I have replaced U7 through U11 with new. Any troubleshooting suggestions?

#2 3 months ago

When I have seen this, it is usually a problem with U7 or its socket/traces.

Remove U7 and then try to boot it. Same or does it stop after 1 flash?

#3 3 months ago

If it boots on the bench, it could very well be the sol. driver board. I've had this come up recently two times. Use one out of your other games to confirm.

#4 3 months ago
Quoted from jj44114:

Remove U7 and then try to boot it. Same or does it stop after 1 flash?

Stops after one flash.

Quoted from snyper2099:

Use one out of your other games to confirm.

Other MPUs in this game work fine, confirming the problem is with this MPU, not the solenoid driver board.

#5 3 months ago

Here's an interesting observation. On the bench after the 6th flash, I was going to short top of R17 to R23 to "trick" the 7th flash. What I noticed was that just touching one end of my jumper probe to the top of R17 (the other end not touching anything) that I got the 7th flash. I did this several times to confirm that I can force the 7th flash by just touching one of the jumper to R17 and the other end of the jumper floating free. Could this somehow be normal, or does this help diagnose the root cause of my problem?

#6 3 months ago

Oh, I see. I missed the part where it restarts consistently on your bench... Andrew may be able to help with better suggestions.

I have been able to trick the 7th flash buy standing barefoot near my bench and touching GND on the MPU. Sounds like that is what you were experiencing. It's normal behavior, from my experience.

#7 89 days ago

Attaching pictures of the board. The U8 socket repair is an ugly one, but I have performed the continuity checks shown for U8 in the pinwiki and all appear to check out correctly. I have also replaced U7 and U8 with known good chips.

IMG_2863 (resized).JPGIMG_2865 (resized).JPG
#8 88 days ago
Quoted from JethroP:

Here's an interesting observation. On the bench after the 6th flash, I was going to short top of R17 to R23 to "trick" the 7th flash. What I noticed was that just touching one end of my jumper probe to the top of R17 (the other end not touching anything) that I got the 7th flash.

I've seen the same thing. With the MPU board out of circuit it doesn't take much noise on that point to trigger the zero crossing detector.
Question is when you did this, does the board reboot after that 7th flash? Does the LED go dim?

Can you measure the frequency out of the 555 timer (pin 3 of U12)?

Essentially it sounds like you're getting stack overflow/corruption of the RAM at U7 either because of bad address line connections to it, or the display interrupt generator running at too high a speed causing the RAM stack to overflow after the 7th LED flash and the game begins initialisation.

FYI, the RAM test on power up only tests that data read was the same as data written. It does not test that data was written/read to/from the expected RAM address. So the RAM test can pass even with a disconnected address line at the RAM chip. U7 RAM is barely used until the 7th LED flash occurs after which the game populates RAM with system/game data and corruption can cause crash/reboot behavior.

#9 88 days ago
Quoted from Quench:

does the board reboot after that 7th flash? Does the LED go dim?

Yes, after the 7th flash the board reboots. The LED doesn't go dim, it just starts the reboot over (i.e., one flash, pause, then 5 more flashes, then after the 7th flash starts all over).

Quoted from Quench:

Can you measure the frequency out of the 555 timer (pin 3 of U12)?

No, I don't have a scope or frequency measuring DMM. I do have a new 555 I could install if that would be something to try.

#10 88 days ago
Quoted from JethroP:

Yes, after the 7th flash the board reboots. The LED doesn't go dim, it just starts the reboot over (i.e., one flash, pause, then 5 more flashes, then after the 7th flash starts all over).

Just confirming, this also happens when you fake the 7th LED flash with what you noticed in your "interesting observation" by just touching the top of R17

Quoted from JethroP:

I don't have a scope or frequency measuring DMM.

Get yourself one of those cheap $10 - $20 LCR testers from China or locally - look on ebay, there's hundreds of them. They're useful for testing all sorts of components (I use them to test ESR of capacitors and SCRs) and get one that includes frequency counter functionality.

I've got one of these - yes the plastic case is amateur but it does the job.

ebay.com link » Tft Gm328 Transistor Tester Diode Lcr Esr Meter Pwm Square Wave Voltmeter Ld Pl

These problems are nearly always related to the battery corrosion - possibly something around the U8 repair that's upsetting U7 maybe on the top side of the board under the socket.

Have you verified connections to the U7 RAM pins are ok.

With U7 removed, what do the pin receptors in the U7 socket look like?

The 555 area looks ok on your board, since you can't quickly test it I'd leave it for later.

#11 88 days ago
Quoted from Quench:

Just confirming, this also happens when you fake the 7th LED flash with what you noticed in your "interesting observation" by just touching the top of R17

Yes

Quoted from Quench:

Get yourself one of those cheap $10 - $20 LCR testers

I've actually been looking at those recently. I will order one today.

Quoted from Quench:

These problems are nearly always related to the battery corrosion - possibly something around the U8 repair that's upsetting U7 maybe on the top side of the board under the socket.

I've thought the same thing. I've hesitated to remove the U8 socket because I'll probably need to repair/jumper most of the connections as the traces are shot. What I have done is verify continuity from the chip legs on both U7 and U8 to the board connections, and confirmed there are do shorts from pin to adjacent pins. At lease I think I didn't miss anything. I believe this confirms that the chip to socket connections are solid.

#12 88 days ago
Quoted from JethroP:

I've hesitated to remove the U8 socket because I'll probably need to repair/jumper most of the connections as the traces are shot.

Yes, pulling that U8 socket out will become a major recovery.

Remove the U8 chip and shine a bright light from the back of the board - look carefully on the top side of the U8 socket pins at board level for any shorts between pins/traces.

You might want to carefully clean the flux from the U8 socket repair so you can get a better look - depends if you want to take the risk.

Quoted from JethroP:

What I have done is verify continuity from the chip legs on both U7 and U8 to the board connections, and confirmed there are do shorts from pin to adjacent pins.

Since there's traces running between pins, you actually need to test for shorts from pin to trace aswell - i.e. shorts won't always appear on adjacent pins.
I use an old fashioned analog multi-meter for doing this. Set the meter for low resistance mode. Meter lead on pin 1 of the chip. Other meter lead on pin 2 and slide that lead across all pins on the chip. When I see the meter needle swing faster than usual I know to recheck those pins for a short. If nothing turns up with pin 1 then move to pin 2, do the same with pin 3 and all other pins until you get to the last pin on the chip.
You can do it with a DMM, I just prefer an analog meter for this due to the instant feedback I get from the meter needle.

Note there are some pins on U8 that are connected together - go by the schematics.

#13 88 days ago
Quoted from JethroP:

Yes

I've actually been looking at those recently. I will order one today.

I've thought the same thing. I've hesitated to remove the U8 socket because I'll probably need to repair/jumper most of the connections as the traces are shot. What I have done is verify continuity from the chip legs on both U7 and U8 to the board connections, and confirmed there are do shorts from pin to adjacent pins. At lease I think I didn't miss anything. I believe this confirms that the chip to socket connections are solid.

check u8 connections back to the cpu chip and the enabling stuff. A lot of the connections at U8 go off in multiple directions. Even if it connects to u7 to may not connect to the cpu/roms/pia etc.

#14 88 days ago

So what’s up with this? For example, I look at the schematic and see nothing connected to pins 1-4 on U8. But the pinwiki shows connections to those pins, which I have confirmed on my board. Something missing on the schematic?

1D1F5E57-BA91-4D8D-A81E-D6D41026A68B (resized).jpeg82C7BEDF-8FB9-4A33-B1BE-C22808384CE1 (resized).jpeg
#15 88 days ago

That's an error on your schematic, there should be little lines connecting pins 1-4 to the address bus (which is the combined line there for pins 5-7 as well).

Busses should be shown on schematics as fat lines like the stern mpu200 one does to prevent this type of confusion.... gives me an idea to redraw the -35 schematc.....

#16 88 days ago

OK, I've spent most of the day looking for shorts and checking pin/addresses to the schematic. All pins/traces at U7 and U8. I have found no shorts between any of those traces and pins on U7 and U8, and all the connections check with the schematic. I don't think I missed anything, but I've been wrong before.

#17 88 days ago

Have you got an EPROM programmer?

#18 88 days ago
Quoted from Quench:

Have you got an EPROM programmer?

No.

#19 88 days ago

Besides the supply pins to U7 and U8, have you confirmed with a logic probe that you're getting activity on all other pins on those RAM chips?

Grab a jumper wire with alligator clips on both ends. Hook a clip to one side of capacitor C16 (near the 555 at U12). Power on the board. As soon as you see the 6th LED flash, clip the other alligator on the other leg of C16 to effectively short it out. This should stop the 555 display interrupt generator. Does the board reboot after the 7th LED flash?
You might need to try this exercise a few times to make sure you short C16 at the right time.

#20 87 days ago

I saved a totally trashed MPU (U8 pads and traces were all gone). This board is 100% rock solid now. I try to keep my stitching running at 90 degree turns, but sometimes it just isn't possible.

20191007_165048 (resized).jpg
#21 87 days ago
Quoted from Skidave:

I saved a totally trashed MPU (U8 pads and traces were all gone). This board is 100% rock solid now. I try to keep my stitching running at 90 degree turns, but sometimes it just isn't possible.[quoted image]

That took some patience!

It's a shame warpzonearcade.com's articles are gone, he had one in there about putting u8 in u1 and rerouting the signal there. It was a 6116 instead of a 5101 but in a situation where u8 is totally hosed, viable solution. I did it to one of my mpu200's I should find that board and document it in case someone else wants to do it that way. (Obviously you have to have the board jumpered for 2x2732 in this situation, as well)

#22 87 days ago
Quoted from Skidave:

I saved a totally trashed MPU (U8 pads and traces were all gone). This board is 100% rock solid now.

Let's see a pic of the other side!

#23 87 days ago
Quoted from slochar:

That took some patience!

Thanks, slochar. It's my Zen time. I no longer do this at work since I have my head buried in project management, networking and interfaces. I enjoy (most) board work. When everyone in the house heads to bed, I zone out on pinball.

Quench - here is the front.
20191121_214419 (resized).jpg

#24 87 days ago
Quoted from Quench:

Besides the supply pins to U7 and U8, have you confirmed with a logic probe that you're getting activity on all other pins on those RAM chips?

I am getting activity as follows:
U7: pins 2-9, 12-15, and 17-23
U8: pins 1-7, 9-16, and 20

Quoted from Quench:

Does the board reboot after the 7th LED flash?

Quoted from Quench:

clip the other alligator on the other leg of C16 to effectively short it out. This should stop the 555 display interrupt generator. Does the board reboot after the 7th LED flash?

Yes

#25 87 days ago
Quoted from Skidave:

Quench - here is the front.

Good to see you've dealt with the corrosion, it should last another 40 years!

Quoted from JethroP:

I am getting activity as follows:
U7: pins 2-9, 12-15, and 17-23
U8: pins 1-7, 9-16, and 20

What's the logic probe indicating on the below - hold the logic probe on the pins for the length of the 7 flashes MPU self test:
U7 pins: 10, 11, 16
U8 pins: 17, 18, 19, 21

Quoted from Quench:

This should stop the 555 display interrupt generator. Does the board reboot after the 7th LED flash?

Ok, so scratch the 555 timer as being the problem.

#26 87 days ago
Quoted from Quench:

What's the logic probe indicating on the below - hold the logic probe on the pins for the length of the 7 flashes MPU self test:
U7 pins: 10, 11, 16
U8 pins: 17, 18, 19, 21

All these pins show some level of activity during the 7 flashes.

#27 87 days ago

You got another set of game ROMs you can directly plug in?

#28 87 days ago
Quoted from Quench:

You got another set of game ROMs you can directly plug in?

No, but actually I took this set off of a working board.

#29 87 days ago

I need to see clearer detailed pictures of the board.
Please carefully clean the flux from the U8 socket repair and take photos of the board outdoors in daylight (but not direct sunlight). Full board pics front and back, plus closeups of the corrosion and RAM areas.

Make sure you select the "Original size (no rescaling)" option before uploading the pics so Pinside doesn't squash them.

Pinside_NoScaling.png

#30 87 days ago

ok..here ya go. If you say replace the U8 socket I guess I'm game. Otherwise, anything jump out at you?

IMG_2873.JPGIMG_2874.JPGIMG_2875.JPGIMG_2876.JPGIMG_2877.JPGIMG_2878.JPGIMG_2879.JPG
#31 87 days ago

I was going to remove U8 socket...got out the dremel tool and cut out the middle. Cleaned up what was exposed (which was pretty clean already) and decided to leave the remaining socket intact. See picture. Verified again there were no shorts from pins to traces and all U8 pins terminate to their proper locations.

I further removed U1, U2, U6, U7 and U8 and installed in another working board and verified I got a proper boot. So just to confirm the game ROM's are good, as are U7 and U8.

IMG_2882.JPGIMG_2883.JPG
#32 87 days ago

Look closely at the traces going between the machine pin sockets. I've had a case where the pin and the trace was shorted. It drove me crazy trying to find it.

#33 87 days ago
Quoted from JethroP:

ok..here ya go.

Thanks those are much clearer. I think we discussed it on your previous MPU board thread, carefully pop that plastic cover off the U7 socket and the U11 socket. Those Augut covers come off fairly easily. Lets see what condition the pin receptors in the sockets look like. You can put the covers back on later.

Also can you post pics of the U8 socket (both sides) like I've done below with a bright light behind the board?

MPU_Sockets 004a.jpg

#34 87 days ago

I don't have any sunlight here now...see if you like these with artificial light.

IMG_2888.jpegIMG_2892.jpegIMG_2896.jpegIMG_2900.jpegIMG_2905.jpegIMG_2906.jpeg
#35 87 days ago

On the first pic with the light under U8, try to scrape the crud away between the pins at board level using a pointy metal needle.
There's some bits of crud across the lower side of U7 socket traces - do the same there.

I can't tell from the pictures due to lighting; what is your opinion of the socket pin receptors? Any green corrosion and/or dark tarnished? Pin 1 of U11 doesn't look great. Take a close look at them.

In the picture below is it a piece of shrapnel from the plastic cover circled or something more sinister?

MPU_U11_Socket_PinsA.jpg

#36 87 days ago

I scraped between the pins. Don't see any problems there.
There is no green corrosion on any of the receptors. There is a little dark on pin 1....only pin 1. I cleaned it.
That was indeed a piece of metal shorting pin 15 to 26 on U11. I cleaned it and verified no more short.

I reinstalled the socket covers thinking problem solved...but to my dismay, it's doing the same thing. Could that short have caused any other problems? Now what?

#37 87 days ago

It always amazes me that they run those traces so close to the pins and they don't even have solder mask over them.

One thing about Quench, give him some good clear photos and he'll usually find the problem.

#38 86 days ago

See pictures. I also removed the socket covers for U9 and U10. The pins look new and I didn't see any shorts.
I reinstalled the covers and replaced U9, U10, and U11 chips with known good chips. Problem remains. Board continues to reboot after the 7th flash.

IMG_2909.JPGIMG_2910.JPGIMG_2911.JPG
#39 86 days ago
Quoted from oldschoolbob:

It always amazes me that they run those traces so close to the pins and they don't even have solder mask over them.

Yeah and somehow in the solder bath they didn't bridge.

Quoted from JethroP:

Could that short have caused any other problems?

Doubt it.

What voltage do you measure at the reset line of the CPU (pin 40)? Does it dip the moment it resets after the 7th LED flash?

Quoted from JethroP:

I reinstalled the covers and replaced U9, U10, and U11 chips with known good chips.

Have you replaced U7 and U8 with known good chips? Your U8 looks like a remark/fake with a date code of '50... All the Philips 5101 I get from China have original markings in white printing, newest date codes around '94.

BTW, if you have one of those small brass wire brushes, very carefully clean those tarnished legs on the ROMs both inner and outer sides. Also pop off their socket covers for a quick look.

Grab your multi-meter and set it on resistance mode. Connect the red meter lead to a ground point on the board. Using the black meter lead, measure the resistance on all the pins of U7 and U8 and report them back (or just compare them yourself with another board looking for any anomalies).

#40 86 days ago

A short between upper address bits at/near the CPU chip can cause the 7 flash reset. I had a MPU working OK when set to hot hand, change it to Kiss and it 7 flash crash. Inspecting around the CPU chip, which was a used pull, and it had a whisker of solder at the plastic package shorting two of the near upper most address pins together. That was a rare odd case tho.

Even tho U8 looks rough like the problem is probably around there, at this point I think I'd get some known good ROMs. Your original ROMs have legs that look really tarnished. The Bally POST checksum test is not fool proof too. Those single wipe IC sockets are not the best either.

#41 85 days ago
Quoted from Quench:

What voltage do you measure at the reset line of the CPU (pin 40)? Does it dip the moment it resets after the 7th LED flash?

Measure 5.2V. No, it does not dip.

Quoted from Quench:

Have you replaced U7 and U8 with known good chips?

Yes.

Quoted from Quench:

measure the resistance on all the pins of U7 and U8 and report them back

Spreadsheet attached. I measured the defective board and a known good board, however the good board did not have the game ROM's installed during the measurements. Not sure if that mattered, and not sure how significant the differences are....except for perhaps U8 pin 22. I double checked those measurements and my data is correct.

Quoted from barakandl:

I think I'd get some known good ROMs.

I have installed the existing 3 game ROM chips in another board and it boots fine, so I am assuming those chips are good.

Quoted from barakandl:

Inspecting around the CPU chip, which was a used pull, and it had a whisker of solder at the plastic package

I have installed two different CPU chips with the same result. These CPU chips work fine in my good board.

Resistance Readings.pdf
#42 85 days ago
Quoted from JethroP:

I measured the defective board and a known good board, ...
and not sure how significant the differences are....except for perhaps U8 pin 22.

Lucky you checked another board because my multi-meter gives very different resistance readings that we can't compare.

If you swap the U8 RAM between the boards, does the pin 22 resistance measurement follow the chip or the board?

#43 85 days ago

BTW, I should have mentioned to make sure there's no batteries connected to either board - batteries will invalidate the U8 pin 22 resistance reading.

If you have time it might be an idea to do the same resistance checks on the U9 CPU chip on both boards for comparison.

#44 85 days ago
Quoted from Quench:

If you swap the U8 RAM between the boards, does the pin 22 resistance measurement follow the chip or the board?

Follows the chip.

Quoted from Quench:

make sure there's no batteries connected to either board -

There are no batteries connected to the board.

Quoted from Quench:

If you have time it might be an idea to do the same resistance checks on the U9 CPU chip on both boards for comparison.

Done. Data attached. Highlighted anomalies. Maybe U9 pin 26 not so bad, but pin 4....??? I verified these values, and also swapped U9 chips, and these data points follow the board, not the chip!

Resistance Readings Rev 1.pdf
#45 85 days ago

Yay!!! Problem resolved!
Found high resistance from U9 pin 4 to board. Pulled the cover off U9 socket and found a slightly bent receptor at pin 4. Straightened and reinstalled cover. Tested for good resistance between pin and board. Got 7 flashes on the bench with no rebooting. Installed in game and booted fine! Thanks again for all the help!

#46 85 days ago

Good find. You guys all did a great job.

#47 85 days ago
Quoted from JethroP:

Yay!!! Problem resolved!
Found high resistance from U9 pin 4 to board. Pulled the cover off U9 socket and found a slightly bent receptor at pin 4.

Excellent work!
To be honest I was getting worried this wasn't going to get solved..

Ok, so looks like the interrupt request line on the CPU (pin 4) was defaulting to always active.
When the board is booting and running the self tests, the CPU has external interrupts disabled (it ignores the state of pin 4). After the board successfully passes the tests, it then enables external interrupts and begins to initialise the game and go into attract mode.
If an external interrupt comes in and the CPU can't determine where it came from, this is considered abnormal so the software is coded to simply reboot. That's the condition your board was in.

There are three valid sources of external interrupts to temporarily change the course of what the CPU is doing:
1) The self test button on the coin door
2) The Display Interrupt Generator (U12) - at 320 times per second it gets the CPU to refresh the display digits
3) Zero Crossing Detector - at 120 times per second it gets the CPU to update game timers (sounds, solenoids, etc), read the switch matrix, refresh the lamps and other system functions

#48 85 days ago
Quoted from Quench:

To be honest I was getting worried this wasn't going to get solved..

After 14 hours and not seeing a reply from you I was getting worried you weren't going to help me anymore! I was always confident with your help it would get solved! And it did.

Quoted from Quench:

There are three valid sources of external interrupts to temporarily change the course of what the CPU is doing:

I don't understand the logic workings, interrupts, code, processor, frequency stuff, etc.... nor do I want to strain my brain at my age to learn it. But I can follow directions and execute recommendations, use a DMM, take pictures, and solder....so I guess I have enough skill to do the repair with the help of experts. Thank you again.

Promoted items from the Pinside Marketplace
From: $ 140.00
From: $ 18.00
Apparel - Men
Pinside Shop
$ 21.00
$ 149.95
Boards
Allteksystems
$ 30.00
Electronics
Third Coast Pinball
$ 9.00
Electronics
Yorktown Arcade Supply
$ 9.00
Cabinet Parts
Third Coast Pinball
$ 149.00
Wanted
Machine - Wanted
Nashville, TENNESSEE
€ 3.95
Flipper Parts
Multigame

Hey there! Got a moment?

Great to see you're enjoying Pinside! Did you know Pinside is able to run thanks to donations from our visitors? Please donate to Pinside, support the site and get anext to your username to show for it! Donate to Pinside