Bally Rapid Fire pinball help

Zinfer

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Recently picked up a bally Rapid Fire pin that has a few issues. Namely, the MPU LED does not flicker or flash at all. Does anyone repair these or have some helpful advice? I looked up the symptoms in the manual and the most it offered was to replace the MPU.
I turn on the machine and just hear the whirring of the fan. That's it. No game play, no attract mode. Checking fuses. There is some acid damage on the edges of the board. I used to get speaker pop, but not getting that anymore. No digits on the led readouts. Seems pretty dead.
This is my first pinball, so I'm learning alot from it.
 
The MPU is an AS-2518-35 and I'm fairly sure the problem is related to acid damage. Still looking into it.
 
Replaced a 2N3904 transistor near the LED indicator on the MPU. One of the legs had seperated from acid damage. No change in behavior unfortunately. I could spring for a CPU replacement kit, but at this point I think it's smarter I try and find someone to repair this MPU rather than shotgunning.
 
Replaced a 2N3904 transistor near the LED indicator on the MPU. One of the legs had seperated from acid damage. No change in behavior unfortunately. I could spring for a CPU replacement kit, but at this point I think it's smarter I try and find someone to repair this MPU rather than shotgunning.

If there's acid damage the first step will be to repair it. If you suspect a problem with the reset circuit and LED driver circuit you can do a manual reset by shorting pin 39 to pin 40 on the CPU (U9) and put a logic probe on pin 39 U11 to check the flashes right at the PIA. Either way it sounds like you've got some corrosion repairs ahead of you.
 
Thanks Lindsey,
I manually reset by shorting 39/40 of U9 and checked it with the logic probe on U11 P39. No reset at all. The LED has never flashed. I used TP3 and GND of the MPU board with the logic probe. I'm thinking of buying that deluxe MPU processor kit from Big Daddy http://http://www.bigdaddy-enterprises.com/repairkits/bally_kits.htm#b-mpubut I'm a bit leary of losing pads from the acid damage. I'm terrible when it comes to lifting pads.

If there's acid damage the first step will be to repair it. If you suspect a problem with the reset circuit and LED driver circuit you can do a manual reset by shorting pin 39 to pin 40 on the CPU (U9) and put a logic probe on pin 39 U11 to check the flashes right at the PIA. Either way it sounds like you've got some corrosion repairs ahead of you.
 
Thanks Lindsey,
I manually reset by shorting 39/40 of U9 and checked it with the logic probe on U11 P39. No reset at all. The LED has never flashed. I used TP3 and GND of the MPU board with the logic probe. I'm thinking of buying that deluxe MPU processor kit from Big Daddy http://http://www.bigdaddy-enterprises.com/repairkits/bally_kits.htm#b-mpubut I'm a bit leary of losing pads from the acid damage. I'm terrible when it comes to lifting pads.

I wouldn't buy that kit at this stage. Could very well be totally unnecessary. Like I said I would start by repairing the corrosion damage. Then from there I would remove all socketed chips, ensure the reset (should go low briefly, then high) and clock are working then install the CPU and a test ROM and go through the rest of the board from there a section at a time (ROM, RAM, Zero Cross, display interrupt generator, etc...). If you want to post a picture of the MPU we can give you a better idea of what corrosion repairs might be needed.

You would want to use TP4 (GND) and TP5 (+5VDC) for the logic probe. TP3 will be around 22VDC and could damage your probe.
 
Initially I took a small toothbrush and a vinegar solution. I then went over it with the toothbrush and a solution of 91% isopropyl alcohol. This evening I then reflowed a few resistors and replaced a corroded 2N3904 just below the LED. Is there something I'm missing as far as repairing corrosion damage? Here's some shots I took tonight of the MPU.
I ran these at much higher resolutions but the max size filters got me so I had to reduce the resolution substantially. I reupped the images on photobucket. http://s269.photobucket.com/albums/jj63/rmassman/


I wouldn't buy that kit at this stage. Could very well be totally unnecessary. Like I said I would start by repairing the corrosion damage. Then from there I would remove all socketed chips, ensure the reset (should go low briefly, then high) and clock are working then install the CPU and a test ROM and go through the rest of the board from there a section at a time (ROM, RAM, Zero Cross, display interrupt generator, etc...). If you want to post a picture of the MPU we can give you a better idea of what corrosion repairs might be needed.

You would want to use TP4 (GND) and TP5 (+5VDC) for the logic probe. TP3 will be around 22VDC and could damage your probe.
 

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No, not a stupid question. I did run some voltage checks but I still need to find what voltages I should be getting on what taps to compare them with.
As some sidenotes, this is my very first pinball repair project so I'm just running into it blindly with the majority of my experience in video cabinets.
I know that when i picked it up, initially I was getting a speaker pop. The LED score display was acting flaky- gibberish, not alot of it. But now I know what to look for, as far as the LED flashes from the MPU. All I hear now is the internal fan, perhaps 2 objects lit on the playfield. I checked all fuses in transformer and power board. I initially made darn sure all those pinballs were not laying around all over the insides of the cabinet. I'll be running some more measurements tonight to ensure I'm getting +5v for my logic probe from tap 5 and using tap 4 for ground.
 
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No, not a stupid question. I did run some voltage checks but I still need to find what voltages I should be getting on what taps to compare them with.
As some sidenotes, this is my very first pinball repair project so I'm just running into it blindly with the majority of my experience in video cabinets.
I know that when i picked it up, initially I was getting a speaker pop. The LED score display was acting flaky- gibberish, not alot of it. But now I know what to look for, as far as the LED flashes from the MPU. All I hear now is the internal fan, perhaps 2 objects lit on the playfield. I checked all fuses in transformer and power board. I initially made darn sure all those pinballs were not laying around all over the insides of the cabinet. I'll be running some more measurements tonight to ensure I'm getting +5v for my logic probe from tap 5 and using tap 4 for ground.

These should be the voltages:

TP4 = GND
TP5 = +5VDC
TP2 = +12VDC
TP3 = +22VDC (unfiltered)

Start by removing all connectors on the MPU but J4. That will isolate it as much as possible for testing. If it boots you know you've probably got a bad display causing the issue. If not, it's time to pull it out of the game and start testing it on a bench. Like I said above, start with the reset and clock circuits and build out from there.
 
Initially I took a small toothbrush and a vinegar solution. I then went over it with the toothbrush and a solution of 91% isopropyl alcohol. This evening I then reflowed a few resistors and replaced a corroded 2N3904 just below the LED. Is there something I'm missing as far as repairing corrosion damage?

You'll need to remove all of the components from the effected areas and sand off the corrosion. That's the only way to really remove it but that corrosion doesn't look that bad. You really need to get the MPU on a bench and see what you're working with. I suspect that you can get it booting without going crazy on more corrosion repairs at this stage. It still needs to be done but I would probably look at it like a preventative maintenance effort after you fix the main problem causing the MPU to not boot.
 
Some pretty wildly different measurements here. With just J4 plugged in, and using TP4 as GND for the meter I get:
TP5=+77VDC
TP2=+69VDC
TP3= +22.62VDC
So I'm very concerned with those major deviations in TP5 and TP2.
I pulled all socketed chips and retested. Essentially same voltages.

These should be the voltages:

TP4 = GND
TP5 = +5VDC
TP2 = +12VDC
TP3 = +22VDC (unfiltered)

Start by removing all connectors on the MPU but J4. That will isolate it as much as possible for testing. If it boots you know you've probably got a bad display causing the issue. If not, it's time to pull it out of the game and start testing it on a bench. Like I said above, start with the reset and clock circuits and build out from there.
 
Some pretty wildly different measurements here. With just J4 plugged in, and using TP4 as GND for the meter I get:
TP5=+77VDC
TP2=+69VDC
TP3= +22.62VDC
So I'm very concerned with those major deviations in TP5 and TP2.
I pulled all socketed chips and retested. Essentially same voltages.

Something is probably funky with your meter. Maybe check/replace the batteries. If those are correct readings you have serious problems.
 
Now that's really strange. I took an old AT power supply on the bench, directly connected the +5v to TP5, +12v to TP2 and a grd to TP4 and I'm getting the same wild readings of 60-80vdc and no flickering or flashing.
 
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Ok, well apparently it was just a bad ground I'd used from the AT PS to TP4.
I hooked up a good ground wire to TP4. The LED is dim now. But no flickering or flashing. The reset button does not work. Shorting pins 39 and 40 of the CPU reset it and I tried shorting the right side of R1 resistor and that resets it also.
I get 6 flashes. Can't get a 7th with the AT PS.
However, when the board first is powered, the LED is always on. It's looking like my ground may have a problem in the cabinet? I know my meters good. It's always been a reliable meter.
I'm going to try throwing the MPU back in the cabinet once more and manually reset it again.
 
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Same thing. Only difference is going from the cabinet I'm completely reliant on J4 for all power. Going to look at the pinouts for J4 I think. The board worked fine on the bench, but I didn't go through J4 at all on the bench.
 
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Ok, well apparently it was just a bad ground I'd used from the AT PS to TP4.
I hooked up a good ground wire to TP4. The LED is dim now. But no flickering or flashing. The reset button does not work. Shorting pins 39 and 40 of the CPU reset it and I tried shorting the right side of R1 resistor and that resets it also.
I get 6 flashes. Can't get a 7th with the AT PS.
However, when the board first is powered, the LED is always on. It's looking like my ground may have a problem in the cabinet? I know my meters good. It's always been a reliable meter.
I'm going to try throwing the MPU back in the cabinet once more and manually reset it again.

Are you getting 6 flashes only with manual reset? If so you've obviously got a problem with the reset circuit which isn't a huge surprise as it's right in the corrosion zone. Time to repair the corrosion and consider a DS1811 reset circuit conversion.

The readings you're seeing in the game can't be correct because all of the ICs would be destroyed by applying that kind of voltage to the +5VDC bus.
 
Same thing. Only difference is going from the cabinet I'm completely reliant on J4 for all power. Going to look at the pinouts for J4 I think. The board worked fine on the bench, but I didn't go through J4 at all on the bench.

If the MPU boots fine on a bench with no manual reset but won't boot in the machine there's definitely a power supply or connector problem. I'm working on a Big Game machine today that had a couple of broken pins in J4 on the MPU. In this case it caused problems with the solenoids but something like that could cause the MPU to not boot. Could also be that the filter cap for the +5VDC is old and crusty.
 
yea, it really strikes me that I had the very same problem on the bench with a bad ground as I did with the MPU in the backbox.
After I connected everything up on the bench the LED was stuck high or on. Then I would short 39 and 40 on the CPU and that would reset it. It would flash 6 times and go out. I'll have to look up this DS1811 reset circuit conversion.
No those readings can't be right. Going to mess with it some more here.

Are you getting 6 flashes only with manual reset? If so you've obviously got a problem with the reset circuit which isn't a huge surprise as it's right in the corrosion zone. Time to repair the corrosion and consider a DS1811 reset circuit conversion.

The readings you're seeing in the game can't be correct because all of the ICs would be destroyed by applying that kind of voltage to the +5VDC bus.
 
Well, I was doing some reading about that. And in my case, if +12v is not present then the LED will be off all the time. I thought it was something like Pin 9 of J4 that held the +12v. Where does that +12 come from? hmm. Filter cap. Are the +12v and +5v coming from the transformer under the cabinet or from the PS to the right in the backbox? It's actually quite difficult with the hinge where it is, to try and get a reading off of J4 connector. Going to go piddle some more.
Thanks for your wealth of information and help. If it keeps up at this pace I might even have this running by tonight. Just depends on what's going on with the +12v and +5v.

If the MPU boots fine on a bench with no manual reset but won't boot in the machine there's definitely a power supply or connector problem. I'm working on a Big Game machine today that had a couple of broken pins in J4 on the MPU. In this case it caused problems with the solenoids but something like that could cause the MPU to not boot. Could also be that the filter cap for the +5VDC is old and crusty.
 
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