SLAM BANG! Turning on my System-1

(Topic ID: 231019)

SLAM BANG! Turning on my System-1


By JethroP

12 days ago



Topic Stats

  • 37 posts
  • 9 Pinsiders participating
  • Latest reply 9 days ago by JethroP
  • Topic is favorited by 1 Pinsider

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#1 12 days ago

My Gottlieb Close Encounters is playing perfectly, but makes a heck of a racket at power up. If the power has been off for more than about 3 minutes, then when I turn the power on SLAM BANG all the solenoids fire at once, the game goes into tilt, and the credit button doesn't do anything. If I turn the power off and back on it boots normally (and quietly), and everything is fine. If I turn the power off for less than 2 minutes, then when I power it back on everything is normal. It only does this crazy thing if the power has been off for more than about 3 minutes.

This game already had the battery removed from the Control Board when I bought it. I wanted to install the RAM backup battery for high score memory, etc., so I added a remote 3-AAA battery pack (with blocking diode). This SLAM BANG issue didn't start until I hooked up the batteries. I did some experimenting...

If I only install 2 batteries (approx. 3V) the same thing happens.
If I only install 1 battery (approx. 1.5V) everything seems to work fine. What's going on? Is this the solution to the problem? The literature shows the battery is supposed to be 3.6V.

The slam switches are closed as required.
The power supply has all new caps and voltages are correct.
All grounding mods have been done.
Diodes (7) have been added in harness between Control Board and Driver Board.

#2 12 days ago

The batteries should be in series so installing only one or two shouldn't work at all. Can you show your wiring?

#3 12 days ago

Yes, when I used 2 or 3 batteries they were in series. Picture shows where I hooked up the batteries. Schematic shows what I tried. You say if I use one or two batteries that will not work. I am here to tell you that when I used 2 or 3 batteries it did not work. It only works with I use one battery. I can live with this as a permanent solution because it is working, but I don't understand why?

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#4 12 days ago

You might want to try replacing C31 and C32 or possibly Z2. The caps are related to these two one shot timers. They make up the power up reset circuit and the chip is actually powered by the battery power VAB. Try the caps first. I recall fixing a few boards with flaky power up delays by working on that circuit.

Also, don't forget there is typically a 0.7 voltage drop across your diode so the 1.5 becomes 0.8VDC.

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#5 12 days ago
Quoted from JethroP:

If I only install 2 batteries (approx. 3V) the same thing happens.
If I only install 1 battery (approx. 1.5V) everything seems to work fine.

If you are getting any voltage at all when other than three batteries are installed you have a short. Removing any battery should be creating a break in the circuit and provide zero volts.

#6 12 days ago
Quoted from YeOldPinPlayer:

If you are getting any voltage at all when other than three batteries are installed you have a short. Removing any battery should be creating a break in the circuit and provide zero volts.

Look at my pictorial schematic. Not sure how to show how I wired up the batteries any simpler than that.

#7 12 days ago
Quoted from CactusJack:

You might want to try replacing C31 and C32 or possibly Z2. The caps are related to these two one shot timers. They make up the power up reset circuit and the chip is actually powered by the battery power VAB. Try the caps first. I recall fixing a few boards with flaky power up delays by working on that circuit.
Also, don't forget there is typically a 0.7 voltage drop across your diode so the 1.5 becomes 0.8VDC.
[quoted image]

That's worth a try. I'll change the caps.

#8 11 days ago

Changing the caps often helps in reset problems.

In a battery-backed up CMOS RAM, the current is so low that the usually stated 0.7V drop across a diode is actually much less, about 0.2V even in silicon diodes. Anyway you should be able to use three batteries.

#9 11 days ago

I haven't changed any caps on the control board (yet). I have one battery w/ blocking diode (1N4004) hooked up to the board and EVERYTHING works fine. RAM is saving high scores and audits, and at power on everything is quiet....just like it's supposed to be. I measured the voltage drop as follows:
Power off, voltage at battery (before diode) 1.6V
Power off, voltage at control board, 1.36V
Power on, voltage at battery, 1.6V (the diode is working).
Power on, voltage at control board, 4.36V
So there is 0.240V drop across the diode, and the 4.36V with power on looks right (I'm assuming).

Again, if I hook up 2 or 3 batteries, the power on event is scary.

I don't know, I'm inclined to just leave all alone and use one battery rather than chase an unknown. I guess I'm looking for some definitive answer to what is going on.

#10 11 days ago

It's working through luck more than anything. If you've got a Philips brand 5101 RAM, their spec says data retention voltage can be as low as 1 volt. Most other 5101 spec for retention is down to 2V only.
You've likely got a problem in that reset circuitry cactusjack posted above. The CMOS 4528 chip at Z2 will work down to a voltage around 3V (2 batteries). Lower voltage than this and it's off/unstable.
Looks like Z2 is used to pulse the reset line to the CPU on startup and my guess with Z2 having proper battery power is that it's not getting triggered or it's pulsing too quickly. Capacitors C31 and C32 affect the pulse period.
Diodes CR37, CR38 and transistor Q5 are used to sense valid power on startup and trigger Z2 so it holds the CPU in reset until power is stable.
This is my best guess.

#11 11 days ago

Quench, that's all very interesting. So what would be your repair recommendation? Thanks for your input.

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#12 11 days ago

With the game on, what voltages do you measure across diode CR37, zener diode CR38, all legs of transistor Q5 and pins 4 and 11 of Z2?

#13 11 days ago

Across CR37, 0.6V
Across CR38, 3.45V
Q5, E=4.3, C=4.25, B=3.49
Z2 pin 4 and 11 both 4.25V

#14 11 days ago

Those readings look ok to me.
Have you got a logic probe?
With the problem, are the solenoids momentarily thunking on power-up or are they locking on?
Sorry, I've got to head off. Maybe someone else will follow up and/or you could try replacing C31 and C32 as cactusjack suggested.

#15 11 days ago

I do have a logic probe. The solenoids do not lock on. It is momentary.

#16 11 days ago

Hook up the three batteries again to the MPU board.
Connect the logic probe across the batteries so it has power with the game off.
Set the Logic probe switches to CMOS and Pulse and put the probe on pin 6 of Z2.
Power on the game, does the logic probe briefly indicate any change on pin 6 when you power on? If you don't notice anything, power off, keep the logic probe on pin 6 and change the logic probe switch to MEM (memory) and power back on. If there was a change the logic probe will remember it.

If you're not getting any change, Z2 is suspect. If you are getting change the pin 6 pulse could be happening too quickly; C31 and C32 could be suspect.
Good luck.

#17 11 days ago

I just finished changing out C31 and C32. No change.

#18 11 days ago

I don't think my probe has a memory function. Before I touch the probe to the pin 6 the green and amber LEDs are on. When I touch pin 6 the green LED on the probe goes out, the pulse amber stays on steady. When I power on the game nothing on the probe changes.

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#19 11 days ago

LATCH switch position on your logic-probe is the same as MEM position I mentioned.
Take it off latch and see if the probe indicators briefly change/flicker at pin 6 when you power on the game and also when you power off. Do the same on the three other output pins of Z2 being pins 7, 10 and 9.
From what I can gather of the circuit:
Output pins 6 should pulse high and 7 should pulse low on power-up
Output pins 10 should pulse high and 9 should pulse low on power-down

Is there battery corrosion on this MPU board around Z2?

#20 11 days ago

There was a modification for the reset circuit in an old Gottlieb service bulletin. You can find the description in
http://tuukan.fliput.net/sys1_en.html#viat

#21 10 days ago

Results: I checked the Z2 output pins when the game starts up with the bang. And I checked them before my 2 minute wait, so I would have a normal boot up. Checked with latch on and with latch off. Pin 6 does not flicker or show pulse at power up/down under any circumstance. Same with pins 7 or 9. No change of state upon power up/down. Pin 10 flicker pulse at power on, sometimes. These results are the same with or without a normal boot.

There is no corrosion around Z2.

I looked at the reset circuit mods provided by Tuukka. It appears I have the newer board, however I checked the resistors (did not remove from the board) and one of them (R159) isn't according to the mod literature. In the circuit I have 2.7M which is what I measured. The mod calls for 3.9M.
I measured as follows:
R159 = 2.7M
R160 is missing
R161 = 43k
R162 = 2.0k
R163 = 6.7k

I'm going to guess the recommendation is replace Z2 because there appears to be no activity at the outputs as expected, right? If this is the case, I have a question. Why does there also appear no activity when I get a normal boot? Should I replace R159 with 3.9M?

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#22 10 days ago

Make sure the trim pot on the power board is ok.

I have a memory of my buck rogers would lock on solenoids when the wiper pin of the (5v adj?? if i remember right) went open.

#23 10 days ago
Quoted from JethroP:

Pin 6 does not flicker or show pulse at power up/down. Same with pins 7 or 9. No change of state upon power up/down. Pin 10 flicker pulse at power on, sometimes.

Can you tell us what the logic probe indicates when you touch ground (pin 8 of Z2) and also what it indicates when you touch power at Z2 (pin 16)? Your logic probe is an old type with indicators I'm not quite familiar with. Just want to understand if green LED off means low and on means high or if orange LED on means low and red LED on means high.

Can you also tell us what your logic probe is indicating at those four output pins of Z2?
Pin 7 should be the inverse of pin 6, and pin 9 should be the inverse of pin 10.

#24 10 days ago

Looks like you have a later revision board that already has the modified reset circuitry. Next step would be to replace Z2, and also check transistors Q5 and Q6.

One common cause for all solenoids on is bad or missing -12V from power supply. So if your power still has the original electrolytic capacitors, they should be replaced, at least C1 and C4.

#25 10 days ago

I appreciate all the help and comments. I hope I'm answering/doing the logic probe correctly.

The 5V trimpot on the power supply was causing a problems early on. I cleaned it, as well as replaced all the electrolytic caps early on. Also replaced a few other parts on the power supply. I have all correct voltages to and from the power supply. That was last week. After all that, I was able to boot up the game for the first time. When I connected the 3 batteries for the board memory functions, that's when I first noticed this BANG on power up. Without the batteries, everything is normal, except I don't have my high score, audits, etc. If I only use one battery, everything is normal too (have all memory functions)...except that it's only one battery!

Probe to pin 8, both amber (pulse) and green (level) LED's go out.
Probe to pin 16, the green is on, and the amber is off.

Probing with power turned off:
Pin 6 green LED off
Pin 7 green LED on
Pin 9 green LED on
pin 10 green LED off.

When the game is powered on, all the outputs are the same except pin 9. It has changed to off.

#26 10 days ago
Quoted from JethroP:

Probe to pin 8, both amber (pulse) and green (level) LED's go out.
Probe to pin 16, the green is on, and the amber is off.

Ok, so green LED off means your probing a logic "low" level and when the green LED is on you're probing a logic "high" level.

Quoted from JethroP:

When the game is powered on, all the outputs are the same except pin 9. It has changed to off.

You mean the green LED is off (logic low) at both pins 9 and 10 when the game is on? If yes, Z2 is very suspect. These two pins should not indicate the same logic level at the same time. If pin 9 is low, pin 10 must be high and vice versa. There is a small chance this could be caused by Z1 since Z2 pin 9 goes to Z1 and Z1 might be pulling it low. With the game on a few minutes, do either of these chips get hot to touch?

#27 10 days ago

Just to confirm I rechecked and MY MISTAKE. Pin 9 is logic high (LED on) both with the game is off and when powered on.

#28 10 days ago

If the Pulse LED doesn't flash and/or the Green LED doesn't change state when you power the game on and off, that Z2 chip doesn't appear to be doing anything and I would replace it.
If your local electronic store doesn't have any 4528 chips, then just run the game on one battery until you do your next delivered parts order.

#29 10 days ago

OK...I will be ordering some parts. Guess this thread will be on hold for a while. Thanks again.

#30 10 days ago

I found a Z2 locally and replaced my bad one. I have 3 batteries in the battery holder. Yippee there is no more loud bang on power up, but OMG now I have another problem that I didn't have before. When I power up now (if the game has been off for a while), the displays, including the 4 digit status display, all show zeros. I can start a game but the scores show zeros. If I power off and back on, then everything is normal. Does this sound like a bad connection somewhere, or something on the board?

#31 10 days ago
Quoted from JethroP:

Does this sound like a bad connection somewhere

Possibly since you had to disconnect the MPU board to replace Z2.

Are the display test modes working?

Are you losing data in the battery backed RAM when it's occurring?

#32 10 days ago

All zeros is slam tilt. Do you have a ball in the game

#33 10 days ago

Not sure how to describe this....in test mode, the zeros kinda fade like I can almost see the digits change, but can't really. They look like zeros, but I can see a change each time I press the white toggle button in the coin door. Just not enough of a change to make out anything but zeros.

I can even start a game, just the digits are zeros.

I am not losing data. If I power off and back on, everything is normal and my data is still in memory. This only happens if the game has been powered off for a few minutes.

I don't believe it is slam tilt. Slam tilt is all zeros immediately at power on. But in my case, there is no display for about 5 seconds, like a normal boot. Then the zeros appear. And as I stated earlier, I can even play a game, just can't see the correct digits or status. It's a normal boot except for the display. Yes I have a ball in the game.

The weird thing about this is that it is similar to before I replaced Z2, in that if I power off then back on within a minute or so, everything is normal. This phenomena doesn't happen on the second boot....only on the first boot after the game has sat a few minutes or longer. Before changing Z2 it was the slam/bang. Now its the display zeros thing.

#34 10 days ago

I have this on my count down sometimes and reseating the side connectors on the mpu fixes it

#35 10 days ago

Game starting correctly only after turning power off and back on is a classic symptom of bad electrolytic capacitor. Replace C1 on power supply. You can also try warming the cap with a hairdryer before turning on, and see if it then starts correctly. Failing caps work a little better when they are warm.

#36 10 days ago
Quoted from Tuukka:

Game starting correctly only after turning power off and back on is a classic symptom of bad electrolytic capacitor. Replace C1 on power supply. You can also try warming the cap with a hairdryer before turning on, and see if it then starts correctly. Failing caps work a little better when they are warm.

Good tip to know, thanks.

#37 9 days ago

I have rechecked the side connectors at the MPU that go to the displays. They are all ok.

I replaced all the power supply electrolytics, including C1, a week ago. I suppose I could have a bad new cap....would seem unlikely, but possible. I don't have any way to check the cap. I guess I'll just go buy another one.

Meanwhile, I removed the new C1 and installed the old one. The slam/bang is back. Oh boy.

So plan now is to order a new C1. Waiting for parts.

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