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STERN RECTIFIER BOARD FUSE ISSUE


Muzac

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Hi all,

 

I’ve been diligently restoring an auction bought/unloved Stern Cosmic Princess and I’m finally into the sweet powering up stage.

 

I’ve had all the backbox boards tested and fixed by @Skybeaux and also purchased a brand new rectifier board from RTBB.

 

Upon powering up the 3/4 amp fuse is blowing on the rectifier board and none of the solenoids are working. The displays, GI and switches are all in operation.

 

My manual doesn’t give me a fuse list, can someone please clarify which fuse relates to what?

 

From my research it appears as though the 3/4amp fuse on the rectifier board relates to the high voltage display circuit. I’m a bit confused as the displays (Tangles) are working fine but the solenoids are all dead. I’m happily assuming it’s the solenoid fuse but am not sure[emoji848]

 

Any help would be greatly appreciated. [emoji16]

 

Cheers, Zac.

 

IMG_2209.thumb.jpg.facbc47f5829245c53fc1e7bbe65930e.jpg

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Right! I am sooo close to actually being able to play this game I can’t quite fathom the thought![emoji2] I am incredibly grateful to all you great people on this excellent site, you’ve all been very patient and extremely helpful. [emoji119]I’ll risk stretching the friendship further however as this one last maddening issue stands between me and pinball glory!

 

Primarily, I went over the wiring for the self test button, checked continuity, re-pinned the relevant connectors and voila! I installed a new button and it now works perfectly. Interestingly, it also fixed the display issues I was having (random digits and strobing) and now the displays are working perfectly[emoji736]

 

Sooo, everything is now working fine except the outhole mech[emoji33]

 

I removed the outhole switch, tested it for continuity and it tested fine. Since I was in the neighbourhood I replaced the diode and re-soldered the wiring. It was a bit intermittent in the switch test previously but now it responds perfectly.

 

The problem now is the intermittent outhole[emoji33]

 

When you start a game, it does one of two things: It either continually resets the drop target bank and doesn’t kick out the ball at all or it kicks out the first ball and upon draining continually resets the drop target bank and doesn’t kick out the second ball. If you manually put the ball into the shooter lane it registers each ball and finishes the game properly.

 

For the record, it has also successfully kicked out the ball each time and allowed me to play a complete three ball game (of sorts) a couple of times.

 

When I put it into the coil test, the outhole coil won’t fire. It was firing earlier tonight in the test but now it doesn’t work at all.

 

Any help would be great!! 🤜🤛

 

 

Sent from my iPad using Aussie Arcade

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Sooo, everything is now working fine except the outhole mech[emoji33]

 

When you start a game, it does one of two things: It either continually resets the drop target bank and doesn’t kick out the ball at all or it kicks out the first ball and upon draining continually resets the drop target bank and doesn’t kick out the second ball. If you manually put the ball into the shooter lane it registers each ball and finishes the game properly.

 

When I put it into the coil test, the outhole coil won’t fire. It was firing earlier tonight in the test but now it doesn’t work at all.

 

Next time the problem pops up, try the following.

Open the head box. Grab a jumper wire and connect one end to ground. Very *briefly* touch the other end of the wire on the metal tab of driver transistor Q16 on the solenoid driver board. Does it cause the outhole coil to activate? If not, there's a wiring connection problem between that transistor and the outhole coil. If the coil does activate then that transistor may be suspect or something upstream is causing it not to fire and will need further diagnosis.

 

Let us know what happens.

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STERN RECTIFIER BOARD FUSE ISSUE

 

Thanks gents!

 

Yeah @toads I felt that might be the issue also. I had a good mess around with the drop target switches because they were sticking so I wondered if I had caused an issue. I’ve given them a good clean with cardboard and isopropyl alcohol and they all test fine in the switch test. One of the drops (no#5) wasn’t registering properly initially but seems ok now, so it could be part of the problem still[emoji848]

 

However, when the game starts and the drop target bank starts it’s loop you can stop it by opening the outhole switch manually. Also, I also discovered the outhole switch only has half it’s gold coating left on the larger contact. It tests fine in the switch test now though..

 

Anyhoo, @Quench I took you advice (thanks again[emoji106]) and the following happened:

 

I started a game, the drop targets reset and it kicked out a ball. After the first ball drained it wouldn’t kick it out and the drop target bank started looping. I shorted Q16, the coil fired and kicked out the ball. I then drained ball two, it registered and kicked out ball three. Ball three drained and game over. FYI extra ball was also lit but that didn’t register..

 

Interestingly, from looking at the board closely it appears as though the components in that chain (Q16, CR16 and R34) were all replaced when I sent the boards away to be fixed..(see pic)

 

(As an aside, there appears to be a faulty switch as the score went a bit crazy & the displays were flickering a bit today [emoji849])

 

Ideas anyone?? [emoji51]

 

IMG_2269.thumb.jpg.d0820155a9978259bb37e774ab289f28.jpgIMG_2271.thumb.jpg.e2a9a7774238c66b3a6d7a3112a154ff.jpg

 

 

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Is it trying to kick the ball out each time but can't?

Is there a mechanical issue with the mech?

 

If it's trying to kick it out each time and something mechanical stopping it you will eventually take out the driver tranny.

If this has happened in the past and taken out the tranny and the board has been repaired, the original problem might still be there.

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Out of interest, does anyone know what chain tells the pinny to kick the ball out when the start button is pressed? I’m thinking that because this is also intermittent, it might be worth investigating further?

 

 

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Anyhoo, @Quench I took you advice (thanks again[emoji106]) and the following happened:

 

I started a game, the drop targets reset and it kicked out a ball. After the first ball drained it wouldn’t kick it out and the drop target bank started looping. I shorted Q16, the coil fired and kicked out the ball. I then drained ball two, it registered and kicked out ball three. Ball three drained and game over. FYI extra ball was also lit but that didn’t register..

 

Interestingly, from looking at the board closely it appears as though the components in that chain (Q16, CR16 and R34) were all replaced when I sent the boards away to be fixed..(see pic)

 

 

It means the problem is likely Q16, CR16 or U4 on the solenoid driver board. We can run some tests/measurements - let me come back to you on this.

 

 

Out of interest, does anyone know what chain tells the pinny to kick the ball out when the start button is pressed? I’m thinking that because this is also intermittent, it might be worth investigating further?

 

When you press the start button, the game will activate the outhole coil irrespective of whether there's a ball in the outhole and outhole switch is closed or not. When you lose the ball in play and the outhole switch closes, the game processes the bonus collect, transfers any remembered game state to the next ball/player, activates the outhole coil to kick the ball out and *clears* the memory state of the outhole switch.

Since your outhole coil isn't activating, the game is seeing the outhole switch as closing again and interpreting this as a ball drain with no score so the game just resets the ball in play. This is the reason you're seeing the drop target bank repeatedly reset.

There is electrically no difference in the way the outhole coil is activated between the start of a new game and a ball drain mid game.

 

Since grounding the metal tab of driver transistor Q16 activated the outhole coil, there is an intermittent problem with the solenoid driver board activating that transistor.

Edited by Quench
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It means the problem is likely Q16, CR16 or U4 on the solenoid driver board. We can run some tests/measurements - let me come back to you on this.

 

Since grounding the metal tab of driver transistor Q16 activated the outhole coil, there is an intermittent problem with the solenoid driver board activating that transistor.

 

Ok so next time the problem occurs, gently pull on the red-black wire at pin 8 of the J5 connector on the solenoid driver board - that wire goes to the outhole coil. See if there's an intermittent connection there.

Next, prod the Q16 transistor a little to see if there's an intermittent connection to it.

 

Then hook up your jumper wire to ground again. Carefully and very *briefly* touch the other end of the wire on pin 8 (bottom left pin) of the U4 chip on the solenoid driver board. Does the outhole coil activate?

If not, disconnect your jumper wire and now hook up one end to test point TP6 on the solenoid driver board. Very briefly touch the other end of the wire on the non-banded side (lower leg) of diode CR16, then try the upper leg of diode CR16. See if the coil activates.

These brief connections are basically activating the coil drive circuitry manually.

 

From experience these intermittent coil driver board issues are usually the diode (CR16 in this case). Looking at your pic the soldering on its lower leg looks a bit suspect.

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Can you grab your mult-meter and set it to DC voltage. If it's not an autoscaling meter set it to the 20V scale. Black meter lead on ground.

When the game is stuck trying to kick the ball out, what voltage do you read on the top leg of diode CR16? Do you see the voltage briefly change every time the game tries to activate the outhole?

Out of interest also measure the voltage on the lower leg of diode CR16.

 

Also measure the voltage on the top leg of diode CR11 - this diode is in the drive circuit for the drop target bank reset. It will give you an indication of meter reading behavior when the drop target coil is told to activate.

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STERN RECTIFIER BOARD FUSE ISSUE

 

Righto! I wasn’t expecting you to be so prompt (you legend!) so I decided to reflow the solder on diode C16 in the meantime. When I took the board out it looked like there was new solder on the component side and old on the bottom. This made me think it all wasn’t flowed together so I reflowed both and now I can’t get the game to fault again. It kicks out the ball every time[emoji846] This is obviously good news “if” it doesn’t happen again! I’ve put through at least a dozen games (still doing it now) and so far, so good! Solenoid test seems to work without fail as well[emoji846]

 

The odd thing is that now the displays are all over the place again[emoji849] During the display test some numbers are correct but others aren’t and some flicker. Is this circuit related at all? If not I’ll look into that chain, doughy connectors may be at play.

 

 

 

 

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Cool.

Displays are unrelated to the solenoids. Likely a connector issue. Wiggle connector J1 on the MPU board during display test mode and see if it affects the display behavior. Is it happening on every display or just some displays?

If you can post a video or even pictures of the bad behavior I can probably better pinpoint the issue.

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STERN RECTIFIER BOARD FUSE ISSUE

 

Ok, I think it’s time I closed this thread, it started out as one thing and now has become something else entirely! I can’t go on forever leaning on you all for every quirk that turns up but I also can’t promise I won’t be harassing you good people again! [emoji16] I can’t quite believe that this big hunk of unloved metal is now finally, and really becoming the game it was destined to be[emoji2] So satisfying to bring back from the dead....

 

Words cannot express how grateful I am to the AA community for the help. What I really like is the patience that you all have for hacks like myself. I love pinball and working on pinnys, learning the electrionic side of things fascinates me and I’ve learnt a whole lot of new tricks with this project.

@Quench you are a living legend and @greydog, @Boots, @Dedrok, @Autosteve & @wiredoug you all truly rock! I own a bar in the CBD of Adelaide (with a Sinbad onsite) and if any of you are in the area get in touch and I’ll shout you a beer and some pinball!

 

I’ll update my resto thread soon and look forward immensely to playing some pinball again.

 

Cheers gents! [emoji481]

 

Zac

 

 

Sent from my iPad using Aussie Arcade

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STERN RECTIFIER BOARD FUSE ISSUE

 

@Quench, you champ, helping at every turn! It’s definitely J1 mate, I’ll repin the connectors and that should do the trick!

 

 

Sent from my iPad using Aussie Arcade

 

90% of what I do is connectors in every repair.

People laugh, but it’s true.

 

Every game I get in, I will start at the beginning.

 

New 3m line chord $3 at Bunnings

 

Repinning of rectifier board with 0.156 trifurcon

 

Check voltages and earth strap.

 

Repinning Sol board 0.1 connectors

 

Check Sol board voltages

 

Repinning all MPU 0.1 connectors

 

Then chase problems.

 

Check coil ohmage

 

 

Sent from my iPhone using Tapatalk

Edited by Dedrok
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90% of what I do is connectors in every repair.

People laugh, but it’s true.

 

Every game I get in, I will start at the beginning.

 

New 3m line chord $3 at Bunnings

 

Repinning of rectifier board with 0.156 trifurcon

 

Check voltages and earth strap.

 

Repinning Sol board 0.1 connectors

 

Check Sol board voltages

 

Repinning all MPU 0.1 connectors

 

Then chase problems.

 

Check coil ohmage

 

 

Sent from my iPhone using Tapatalk

 

I find a lot of problems on Bally, Stern and Williams SS machines around the 6800 and 6821 sockets if they are still original. Amazing how many machines I have got to boot up by probing a pin or needle between the chip's leg, one leg at a time, and that legs hole in the socket. Very rarely the chip is at fault. Makes me wonder how many 6821 chips were changed for no reason but the machine magically worked having a new chip put in a dodgy socket, for a little while.

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I find a lot of problems on Bally, Stern and Williams SS machines around the 6800 and 6821 sockets if they are still original. Amazing how many machines I have got to boot up by probing a pin or needle between the chip's leg, one leg at a time, and that legs hole in the socket. Very rarely the chip is at fault. Makes me wonder how many 6821 chips were changed for no reason but the machine magically worked having a new chip put in a dodgy socket, for a little while.

 

Or take them out, check the socket, re insert.

 

 

 

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Or take them out, check the socket, re insert.

 

 

 

Sent from my iPhone using Tapatalk

 

I like to re-align any chip's legs if I remove the chip from a socket. One side of the chip's legs on a piece of glass, chip 90 degrees to the glass. Place a wooden ruler half way up the other side of those legs touching the glass and put a very slight bend in the legs exactly as they come from the chip manufacturer. Turn the chip around and do the same to the other row of legs.

The chips never had dead straight legs when brand new but straighten when inserted in the socket a couple of times.

 

If I have no joy but found a pin not connecting reliably doing the pin probing testing, I replace the socket.

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