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.

Power supply is a brand new Swemmer.

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.

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.

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

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

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)

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 !

Not off but looks split open

Fixed, but no change

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:
image.jpg

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

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??

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.

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.

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.

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.

"http://www.pinwiki.com/wiki/index.php?title=general#Testing_a_Bridge_Rectifier"

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.

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.

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.

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.

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

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.

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?

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

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

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.

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

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.

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.

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.

I'll jump out a window if he says everything is good! Lol.

Boards are back to Fred. We'll see what he says....

Well Fred said there was nothing wrong with the boards....so I guess I'm screwed. I don't know what else to check. I've replaced every edge connector, every molex pin, caps, boards, fuse block and fuses, bridge rectifiers...ugh !

Anyone know how to test the voltage coming directly out of the transformer? I haven't tried that...not sure it's the problem but I need to try and eliminate everything in the bottom cabinet.

I don't think the connectors are the issue since I unplugged all connectors except J1 and I still get the voltage drop when plugging in J2. I think maybe the transformer isn't pushing out what it should when J2 gets plugged in...remember no other connectors are connected I've unplugged every single other plug trying to narrow it down to a connector.

Replaced all fuse holders, but I will double check them.

On a small side note....anyone know how to keep the star gate ramp tube in place? Is it supposed to be glued to the factory plastic straps??

Dang! Mine still slides little by little.

So with DMM set to DC put one lead on one terminal of the cap and the other lead on the other? Does it matter which goes on which? Should it be done with power on? Also on my schematic it shows pin 2 as the ground, not 1 or were you referring to the lead color?? Thanks for answering these beginner questions. I'm pretty new to this, but trying to learn!

I was going to try some weld-on gel

The first reading I took with everything unplugged except J1 and power on was 14.3. DMM black probe on "-" and red on "+". DMM on DC. Dial set at 200 in the section marked V.
With J1 and J2 plugged in it reads 13.1

I might have just figured it out(maybe not sure yet). The IC Chips are on the MPU board with the blue clamp down holders (the ones with the little lever on the side). Pretty sure one or more of the chips weren't centered when I received this new board. When the MPU was shipped back to Fred and tested in another machine he must have centered the chips (I never checked them when I first got it). I just popped in my old MPU and I got no voltage drop. My old MPU has the chips soldered in. Also when the MPU was shipped back to me Fred said to make sure the chips are centered, however when I got the board back it was damaged so I returned it today. When I receive the replacement I'll test my theory. But it's all I could think of. Would an off center chip cause that voltage drop??

Right! And I never did check the seating of those chips! Been pulling my hair out. We'll see what happens when the MPU board comes back from Fred.

Ok so the replacement MPU board will be here tomorrow and I want to make sure that once the machine is delivering a steady 5.0 volts with both A2J1 and A2J2 connected to the Power supply board and A2J2/A1J1 connected to the MPU that I get the correct order of systematically plugging things in to check for problems. What order should I go in? Displays first then interconnect, play field switches, lamp drivers and soundboard last ??
Thanks for any help in powering this thing up correctly!!

Ok. Getting 5.0v with everything hooked up. Game booting. Go to start a game and all the lights on the play field blink in unison and the ball won't kick out. There are 3 balls in the trough but aren't advancing. Never had this issue prior to this. Where is the best place to start on this problem. If the trough switch isn't working would all the play field lights blink in unison? I can't remember if it does this in waiting for the ball to kick out. Little by little ill get this baby bulletproof!! (I hope...lol)

The solenoid tests all worked but like you just said the solenoid that first feeds the balls into the trough was very weak. What exactly do you mean by a "stuck" switch ?? Thanks !!

I couldn't locate any stuck switches. Actually the solenoid that kicks the ball up the trough to the solenoid that pops it out to the shooter lane is fine. I had thought it was weak because it was trying to flip 3 balls up the trough. When it does them one at a time it is fine. It will only kick the first ball up though.

Still trying to find out why the balls don't continue to advance and the game won't start. Credits register when coins are inserted, press credit button and player one flashes zero as it should, drop targets don't reset, play field continues to blink and ball doesn't eject.

Also...The trough has all 3 balls in it, past the first switch and on the second switch. The eject solenoid works during the solenoid test so it has to be something with the last switch before the eject solenoid, no??

I'm going to start a different thread with the start up issue since my power issue has been solved. Thanks to everyone who tried helping on that one! On to this new one. Can someone close this thread as fixed, solved or however that works?? Thanks again folks !!