(Topic ID: 133759)

System 80 power issue

By Gr8snook09

7 years ago

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  • 80 posts
  • 11 Pinsiders participating
  • Latest reply 7 years ago by Gr8snook09
  • Topic is favorited by 5 Pinsiders


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There are 80 posts in this topic. You are on page 1 of 2.
#1 7 years ago

I'm in a battle to find out where I'm losing power on my pinball machine. All boards are brand new. I've changed all edge connectors as well as replaced all molex male and female pins, replaced the big cap in the bottom of the machine. Replaced the bridge rectifiers. With just the power supply plugged in I get 5v, but as soon as I plug in the MPU (with no edge connectors connected at all) it drops to 4.3. Not sure what to look at for this drop?? Oh it's a Mars God of war. I've been struggling with it for like 5 months now. Very frustrating to say the least.

#2 7 years ago

When you put a load on the line, there will always be a voltage drop--not usually quite that much, though (usually it only drops about 0.1v to 0.3v). In any case, take a multimeter and measure the voltage on the MPU and then adjust the POT on the power supply until the MPU gets 5v.

Have you done any work on the power supply?

#3 7 years ago

Power supply is a brand new Swemmer.

#4 7 years ago
Quoted from Gr8snook09:

Power supply is a brand new Swemmer.

The same advice applies if there is a POT adjustment, but I'm not familiar with those replacement boards. You might have to contact Frett Swemmer directly for support on those.

#5 7 years ago

The board is the same as a factory one. The voltage drop is too great for a pot adjustment. Something else is going on with the machine. It's not the board. Hence my dilemma trying to track the problem down.

#6 7 years ago

I'd try powering the MPU on the bench, with a PC power supply, and read the voltage drop. If it powers up, stays around 5v, and doesn't shut down the PC power supply, then I'd suspect the power supply board.

#7 7 years ago

It could be a short on any one of the chips on the MPU. Do any feel hotter than the rest? I can't remember if the 6532s run a little hot any way, perhaps someone can chime in.

#8 7 years ago

MPU is brand new as well. All boards are brand new, connectors have all been replaced. Big cap in bottom cabinet replaced, bridge rectifiers all replaced.

#9 7 years ago

Im not sure what is driving that voltage drop at all.

#10 7 years ago

It's not normal that when powering the MPU board that a 0.7 volt drop occurs correct ??

#11 7 years ago
Quoted from Gr8snook09:

MPU is brand new as well. All boards are brand new, connectors have all been replaced. Big cap in bottom cabinet replaced, bridge rectifiers all replaced.

Just because it is brand new doesn't mean it doesn't have a defective component.☺

No, there should not be a 0.7v drop on the 5v supply. There is a component on either the PSB or MPU that is bad. Do you have access to any other working boards compare?

Have you contacted the manufacturer for advice?

#12 7 years ago

Fred said there is resistance somewhere or "dirty power". Not sure where to look for that especially with a new cap and bridge rectifiers down below. Not sure what is causing it. I really doubt it's the boards as he sent video with serial numbers of them in and working the day before shipping them out. Without the MPU hooked up my 12v is reading low at the test point on the power supply. The readings are as follows:
TP1 65.1 (60v)
Tp2 47.4 (42v)
Tp5 6.4 (8v)
Tp4 5.0 (5v)
Tp6 9.8 (12v)

#13 7 years ago

I found a small spot of exposed wire on the "+" side of the 8v bridge rectifier (it wasn't contacting anything, just in the open air). Is that enough to cause a problem like this at all ?? Thanks guys !

#14 7 years ago

if the wire has come off the 8v + bridge you will loose power

#15 7 years ago

Not off but looks split open

#16 7 years ago

Fixed, but no change

#17 7 years ago

When I plug in the J3 plug (only J1 and J3 plugged in J2 unplugged)I still have 5 volts. My surround red lights circle the backglass but my displays show this:

When I then plug in J2 the voltage drops to 4.3, the red lights circle the backglass extremely fast and displays are out.

#18 7 years ago

Put in a different power supply...same result, put in another MPU board same result and voltage drop. It's something somewhere else. Just don't know what would cause it. I guess it lies with tilt/slam or non controlled lights??

#19 7 years ago

How do you test the output of the bridge rectifiers in the bottom cabinet while under power? I see how to test them in general (they all tested as shown on pinrepair at between 4-6 volts in diode testing), but not how to test what is coming out of them. Thanks.

#20 7 years ago

First, don't connect or disconnect displays with the power on. This includes J2 and J3 on the MPU. Doing so will fry the 7448 display drivers on the MPU.

With power off, disconnect display connectors for player 2 and player 4. Power on. Measure your 5V.
Power off, reconnect player 4. Power on. Measure your 5V.
Power off, reconnect player 2. Power on. Measure your 5V.

Report results.
Don't worry about the chaser lamps. Let's get the 5V fixed first.

BTW, there is a System 80 section in the PinWiki.
Chris Hibler - CARGPB #31
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#21 7 years ago

All plugging and unplugging has been done with the power off. I want to start from scratch and test all the AC voltage first then the bridge rectifiers and make sure all the power down below is good. My problem is I did this so long ago (first time I've ever done it) and now I forgot how to do it. I have the service manual and an education so with basic instruction I should have no problem. I've read the system 80 pinwiki but I didn't see a basic AC testing section starting with transformers through fuses, main capacitor and then bridge rectifiers. Once I can establish all that is clean I can go from there. I have replaced the cap, the bridge rectifiers,all connectors (except 5 display ones), all molex male and female pins, all fuses and bottom fuse block, so I just need to make sure proper AC voltage is present and then proper dc. Oh. All boards are brand new as well....unfortunately I'm new to using a DMM and need my hand held as to where to put the leads. Thanks for jumping in Chris. I know you have a bunch of knowledge about these system 80 games.

#22 7 years ago

Oh. It measures 5v at all times except when J2 gets plugged in. Then it drops to 4.3 regardless of if displays are plugged in or not.

#23 7 years ago

The Swemmer power board is more or less a direct copy of the original. It has a voltage adjustment on the board. Might just need adjusting.

#24 7 years ago

It doesn't quite adjust enough to go from 4.3 to 5.0. Fred said there is something else going on. That's what I wanted to track the power from cord to board.

#26 7 years ago


This is not what I was asking for. This is just testing if the bridge rectifiers are good. I want to know how to test them under power. On Mars they show 3 different voltages that come from the 3 different rectifiers. I'm looking for readings of 5v, 12v and 24v(or close to it). I don't see where pinwiki describes how to do that unless I'm missing something.

#27 7 years ago

Actually like I said previously I want to test AC voltage from the cord to transformers thought the fuses to rectifiers, then the dc voltage after the rectifiers.....systematically trying to make sure I'm getting correct power. Should be basic (I would assume) but I don't see any process for doing that.

#28 7 years ago
Quoted from Gr8snook09:

trying to make sure I'm getting correct power

What is "correct power"?

Anyway, if you want to check voltage at some point, voltage is potential so use a multimeter (set to DC/AC volts) and stick one probe on the point you want to test and the other probe on an appropriate ground point. Be careful.

Just curious, when you are testing your power supply board voltages, what are you using for your ground point?

#29 7 years ago

I thought when testing AC there isn't a "ground". Also testing the board I was using the test points of course.

I am still waiting for anyone out there to answer the question as to how exactly to systematicly test the voltage from the power cord through the system up to the power supply. Thanks.

#30 7 years ago

Voltage is potential between a point and some reference. What you use as reference depends on AC/DC and what you are testing. For example if you were testing the AC voltage going into the line filter, you would check between the line and neutral to read ~120V.

Perhaps someone will write the tutorial you are demanding. Good luck!

#31 7 years ago

I'm not demanding anything. Just asking. If no one can effectively convey how to test those various points along the chain I guess I'll just call a pinball repair guy (which I was trying to avoid). I wanted to make sure that the wires are delivering the values they are supposed to. Making sure there isnt any unseen damage to a wire such as a wire that may be broken under the insulation. Not sure how else I would go about checking that. I haven't seen anything online that details that like most other tutorials out there.

#32 7 years ago

These are the 5 areas I'm looking to test.

#33 7 years ago
Quoted from Gr8snook09:

I'm not demanding anything. Just asking.

Perhaps the connotation or phrasing is what led radium to think more in terms of "demanding" vs "asking".
The written word loses so much over personal face-to-face comms.

This isn't the answer to your question, but the way you'd like to go is hardly ever necessary. If you measure the spec AC voltage into the bridge, and the spec DC voltage out of the bridge, that eliminates the need for upstream measurements. The only power measurement left is to measure the AC ripple component of the DC power, which should be next to zero if the filter cap is doing it's job.

So, find a bridge.
Power on.
Red lead on one AC spade (marked with a ~). Black lead on the other (catercorner). Since we are measuring AC, orientation does not matter.
If the AC voltage measures close to the spec voltage (see the manual), that's good enough. It doesn't have to be right on.

Now, set your meter to DC voltage. Black lead on the spade marked with a minus symbol. Red lead on the catercorner spade marked with a + symbol. The DC voltage will be close to the AC voltage input * .812. That is the "perfect" rectification yield for a bridge. In practice, there is no perfect. Expect the measurement to be close.

To measure AC ripple, set your meter to AC volts. Black lead on ground. Red lead on the rectified and filtered voltage, like the 5V TP on the PS (which has also been regulated to about 5V). The AC component of that DC power should be millivolts only.

Make sense?
We're here to help.
Chris Hibler - CARGPB #31
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#34 7 years ago

BTW...you'll always know which lug is ground in a Gottlieb game as they consistently used a green wire with a yellow tracer across the manufacture of at least System 80 games.
Chris Hibler - CARGPB #31
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#35 7 years ago

At the 24vdc bridge rectifier I read 29.9 AC and 25.9 dc
At the 12vdc bridge rectifier I read 11.8 AC and 12.0 dc
At the 6vdc bridge rectifier I read 8.4 AC and 11.1 DC

Last one really seems off.

#36 7 years ago

If I'm reading the manual correctly (God knows if I am or not) but at the 24vdc bridge rectifier shouldn't (ideally)the AC be 25 and DC be 24
The 12vdc bridge AC be 12 and DC be 12
And the 6vdc have the AC be 8 and the DC be 6?
Or am I way off the mark?

#37 7 years ago

None of those voltages are the problem.
I really, really think you have a shorted IC on either the player 2 or player 4 display. Hence the suggestion above.
Chris Hibler - CARGPB #31
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#38 7 years ago

Listen to Chris. The displays use 5VDC for their logic power.

Also note that bad displays can cause damage to your new boards. Heed the warning Do Not disconnect displays with the power on or you will cause damage. In fact do not remove any cables with the power on.

Your player one display may have a problem. Swap player 1 with player 3 display.

Determine which display is causing the power drop -- player 2 or 4. Try the good one in the player 1 position.

Ignoring the player 1 and 3 displays, with player 2 and 4 displays unplugged does the game go into the attract mode where the controlled lamps are sequencing on the playfield?

#39 7 years ago

Even with all the displays unplugged I get the voltage drop.

#40 7 years ago

Is there a way to test those ic's on the displays?

#41 7 years ago
Quoted from Gr8snook09:

Is there a way to test those ic's on the displays?

There is a diode test you can use, but personally, I haven't had success with it. If I suspect a bad IC, I put in a replacement. Although, with voltage issues on those displays, I've been finding that sometimes the resistors fail under load.

However--if all 5 displays are unplugged and you're still getting the voltage drop, the problem probably isn't the displays themselves.

#42 7 years ago

That's why I was starting at the bottom and working my way to the boards since I get the drop when the MPU is connected (with nothing connected to the MPU including the interconnect). Didn't make sense that a bad display would cause a voltage drop when I still get it with no displays connected. I don't think I previously said that the drop still occurred with no displays attached. It happens with J1,2 and 3 plugged in (j2 also connected to MPU) but no other connectors attached or displays. The only other connectors connected are all the molex connectors, the pop bumper boards, the driver boards for the backglass surround lights and the LED strip on the playfield.

#43 7 years ago

One thing I did notice is that Q1 on the power supply was getting very hot with J1, J2 and J3 plugged in.

#44 7 years ago

You say that the voltage drop doesn't start until A1J2 is plugged in. Looking at the manual, A1J2 shouldn't carry 5VDC to the displays, just segment signals unless an IC is shorted out. Normally, with that connector unplugged, you shouldn't see anything in any of the displays. Plugging the A1J2 connector back causes the 5VDC short conflict.

I see this was suggested at the beginning of this thread but I didn't see where it was addressed. I know this has one of those "new" CPU boards in it but have you tried running it in a different game (since you've owned it) to see if the problem is in the CPU board itself? I understand that Fred always tests and videos his boards to prove they work, that's smart business and verifies that the problem is elsewhere.

However, it may be that a unknown existing display issue shorted out something on the new board when you plugged it in and turned it on the first time. This isn't that uncommon as anyone that fixes boards can tell you, even Fred knows this. I always tell anyone I fix boards for that once the board is plugged in and the game turned on, the board can short out again if the cause of the problem isn't corrected too. It may be the same issue that took out the original CPU board and the reason it was replaced by you.

My suggestion would be to send the board back to Fred for testing and have him repair it for you if needed. If it turns out that there is a problem, then, he'll be able to tell you where to look in your game to correct it. Then, don't plug the board back in until you do. If it turns out that the CPU board is good, all you've lost at this point is shipping costs and you're back to looking around for the issue again.

System 80, not just a job, it's an adventure

#45 7 years ago

Just re-read the thread, was looking for clues and found this piece of info. If "none" of the displays are plugged in, then it should be the same as not having A1J2 plugged in even when it is. There would be no display load or short at all. Please verify wire color positions are correct at the credit display A5J1 since it's the only display that is supplied 5VDC in a 6 digit game.

System 80, not just a job, it's an adventure

Quoted from Gr8snook09:

Oh. It measures 5v at all times except when J2 gets plugged in. Then it drops to 4.3 regardless of if displays are plugged in or not.

#46 7 years ago

The wire colors are indeed correct at A5J1. Also at A10J3 and A10J2. The displays are the only edge connectors I haven't replaced. Also I'm sending the power supply and MPU back to Fred to check them out. Im really starting to get confused over this thing. I've started from scratch like 5 times trying to find out what's going on. Took a breather for awhile and now I'm digging back in.

#47 7 years ago

Sorry, forgot to mention checking the other plug A10P5/J5. Make sure the wire colors going into the plug and coming out match. The reason I mention this is because I shot myself in the a$$ a few years ago with my MGoW's and caused a problem that took forever to figure out. I had two of them at one time and decided to sell one. I had one with a real nice playfield and one with a worn out one. Fortunately, I also had a NOS playfield so I decided to sell the more common red cabinet and keep the rarer black one. I swapped the red cabinet playfield out and put in the nicer one to make it an easy sale. At the time, I remember that I had to move some wires around at those plugs because the status display wouldn't work right no matter how many others I swapped into it. I assumed that all MGoW wiring would be the same and it wasn't. If the playfield had been swapped to a different one in your game, it's another "shot in the dark" but worth a look. If it happened to mine, unless you know your games history, it may have also happened to yours?

System 80, not just a job, it's a adventure

#48 7 years ago

I double checked that plug (it's the one on the right side of the backbox that goes to the red lights surrounding the backglass)it's all good. I know the wires going into the other plugs match what's coming out because I just changed out all the molex pins after this voltage drop and was extremely paranoid about not matching the wires. I was thinking the same thing about wire colors matching and I actually double checked ALL the connectors....several times !

Could there be a pinched or split wire in the backglass surround causing this at all? I had that apart a very long time ago and may have trapped a wire. Although the machine had worked since I did that.

#49 7 years ago

It's possible that a wire is pinching against something, then shifted as the game was opened and closed, causing a ground short. This happens a lot with the coin door wiring. I would think that with the connectors all disconnected, it would be possible to use a meter on the main 5VDC and ground lines to see if any are touching each other. Unfortunately, this problem is a tough one to diagnose without seeing it first hand. Right now, I'm grasping for anything I can think of. I'm not one to give up on a System 80 issue but I'm running out of ideas that might cause what you see. Question, did you look inside each connector you worked on to be sure there wasn't a piece of a crimp left behind and causing the new crimps to jumper to each other?

System 80, not just a job, it's an adventure

#50 7 years ago

I did not look for pieces of a crimp left behind in the connectors. This specific 5v drop to 4.3v happened prior to me changing out all the molex pins.

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