(Topic ID: 181613)

Medusa Tune Up


By Toyguy

2 years ago



Topic Stats

  • 12 posts
  • 4 Pinsiders participating
  • Latest reply 2 years ago by radium
  • Topic is favorited by 4 Pinsiders

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IMG_1243 (resized).JPG
Photo Feb 25, 6 59 03 PM (resized).jpg
SEB Coils (resized).PNG
IMG_1479 (resized).JPG

#1 2 years ago

Amazingly, a Medusa popped up right in my backyard last week. One of my wish list machines, I snapped it up. It's in generally good shape with a few minor issues.

IMG_1479 (resized).JPG

I could use some advice on the biggest of these issues, the 7-bank targets. When you start a game, they all reset up but then the single target drops and it starts on two targets. 100 points gets scored. The 3 and 4 group work OK. The 5 group misses the rightmost target. I haven't yet tested the 6 or 7 groups. So OK, let's go into solenoid test. All 7 drops work fine in solenoid test so I moved on to switch test.

Problem 1, switch test shows 41 in the display, Movable Flipper EOS. Looking at the Zipper Flipper mech, it looks like there is an EOS on both the left and right flippers but only one switch number is given. Does that mean they both share #41? I take it these should not be closed in switch test?

So even though 41 was blinking away I tried another switch and it briefly showed that one before returning to 41. So I tried the 7 drop targets - none appeared at all, just the 41 kept blinking. Should I have gotten switch closures with the targets down, or is it a quick, momentary sort of thing as they fall?

Let's start with that. There's also some issues with speech getting cut off and a bit of asymmetry in the zipper flippers when they pull in but we'll get to that later

Thanks!
Dave

#2 2 years ago

The drop targets falling when they shouldn't might be due to the solenoid expander board under the left side of the playfield. There's a lamp right next to it that's part of the solenoid expander activation circuit. Put the game in lamp test mode. If that lamp isn't flashing, replace it. Otherwise remove the solenoid expander board and reflow any bad solder joints you see.

From memory, switch 41 is a single switch in the middle of the zipper flippers and comes up closed in the switch test when the zipper flippers are wide open. Lift the playfield and manually activate the coil that pulls in the zipper flippers and see if #41 stops blinking in switch test mode.
The Bally switch test mode only shows you the lowest number switch that's closed. So if all switches 41 through to 48 are closed, the switch test will only report switch #41. Coincidentally the seven upper drop targets are switches 42-48 so until you open switch 41, you won't see the drop targets switches in the switch test.

#3 2 years ago

Thanks Quench! That's extremely helpful and not at all obvious from the manual's diagnostic instructions.

I've been doing more research and it seems that coils without 2 diodes, in some locations, can cause this so I'll also be checking that out. I have a ton of diodes on hand so perhaps I'll just replace them all if the solenoid expander doesn't seem to be a problem.

Off to the basement!

#4 2 years ago
Quoted from Toyguy:

I've been doing more research and it seems that coils without 2 diodes, in some locations, can cause this so I'll also be checking that out.

Oh yes looking at the schematic, I see what you mean. It will be the diodes on the coils you see with one leg connected to either a brown/orange wire or a grey/red wire that might be shorted.

#5 2 years ago

Did a little more testing this afternoon after I had a friend stop by to move the playfield onto the rear lugs. Why didn't they just put rails in like everybody else?

Anyhow, the lamp on the Solenoid Expander was fine, blinking away in lamp test and toggling the relay. I closed up the zipper flippers and was able to test all the drop target switches. Each worked as it should. I did a full solenoid test and it was correct - firing the correct solenoid at the correct time. I'm replacing the solenoid driver and expander board with newer, modern stuff anyway so I'll wait to see what happens with the new hardware installed. If it's still acting up, I'll have to go through the diodes.

#6 2 years ago

I'm not going to claim victory quite yet but I may have a lead on the drop target issue. I decided to begin cutting coils out of circuit one at a time to see if I could learn anything that way. There are relatively few coils driven by the SEB: outhole kicker, knocker, saucer, the 2 drop target bank resets, the 7 individual drop target releases and the zipper flipper open and close. I decided to start with the knocker as it was easy to reach. I clipped the single orange-green (74) wire and started the machine up. The single target stayed up! Went through the series and the targets acted as they should but I think I saw a problem with the zippers opening and closing. This is interesting because, as you can see below, that 74 wire controls both the knocker and the Open Zipper coils, based on the position of the SEB relay.

SEB Coils (resized).PNG

Maybe there's also another issue at play here associated with the SEB, getting its relay pulsed at the wrong times. It's also interesting to note that the original problem 1 drop target and the two zipper flipper coils are on the same side of the relay. I should have the new SEB replacement in hand by Tuesday to see if that helps any. In the meantime, two new diodes for that knocker coil and we'll see if the problem disappears.

#7 2 years ago

For anyone who might search this thread out later, the problem with the progressive drop targets was indeed the diodes on the knocker coil, but not because one was bad. As I was getting set to pull the coil tonight to change the diodes, I was looking at the schematic, making notes and checking wire colors when it struck me - the coil was wired in incorrectly. Unlike most coils, where you have a wire harness lead going to each of the tabs with the thin coil wire attached to it, not so on these Bally dual-diode coils. In this case, the 74 wire was supposed to go to the unbanded side of the diode connected to one of the coil wires, and it did, but the 91 wire was supposed to go to the unbanded end of the other diode, which was the center tab on the coil, without the other end of the coil wire. Instead, it was soldered to the other outer tab. After reconnecting them the proper way, the drop targets continued to work properly, as they had with one lead cut out of circuit. YAY!

Now all I have to do is get these darned set screws to hold for the 4 new flippers and I'll be all set. Even blue loctite isn't doing it; may have to use the red stuff and hope I never have to do it again in my lifetime At least I can get new lower flipper cranks if I need them. Looks like the zipper flipper cranks may be unobtanium.

Besides the set screws, one pop bumper skirt to replace and 3 new translucent targets for the 7-target bank and she's good to go.

#8 2 years ago

Well done

Quoted from Toyguy:

Looks like the zipper flipper cranks may be unobtanium.

These Bally flipper cranks look pretty close to me:

http://www.marcospecialties.com/pinball-parts/A-1889-7
http://www.marcospecialties.com/pinball-parts/A-1889-8

The cranks on my zipper flippers are horribly worn because of metal to metal wear at the plunger pivot. I haven't investigated it yet but I'd like to see if any traditional crank and plunger rod with link from that era can be used instead.

#9 2 years ago

Sir, I also recently got a Medusa and have the EXACT SAME PROBLEM! I've been driving myself crazy by checking everything I'm supposed to check, to no avail. I'm going to run down to my basement now and check if by chance the knocker coil is in the same mis-wire situation. But that would be really weird to have the same mis-wiring. I will report back. I also just ordered a brand new solenoid expander board as you did. Thought it was worth the $40 because this board does seem to control the coils I'm struggling with and my original board had some very sloppy looking reflow work done on it, with a missing plastic cover and looks slightly toasty. In addition to my 7 bank drops not resetting properly, I also get the 41 EOS switch error. Also when either of the drop target assemblies reset, for some reason the ball launch coil also erroneously fires. And when it fires to launch a ball, it seems to be under powered and does not have enough kick to get the ball out of the trough even though the coil and sleeve assembly are good. Also the saucer coil does not kick out the ball even though the switch is working. Basically all the coils on this circuit are not working as they should. It's all got to be related to something similar as on your machine.

I have so far checked the U10 and U11 IC's that drive the switch matrix and coils on the MPU, had the Solenoid Driver Board professionally serviced along with the S&T board and put in a fresh lamp matrix board, reflowed headers, visually inspected for any shorted, twisted, or broken diodes or caps under the playfield, meter checked all the associated switch diodes, checked the solenoid expander light bulb, etc. Still the same problem. : (

1 week later
#10 2 years ago

Got my problem solved with the help of Toyguy and Pinwiki. Basically one simple problem apparently caused the previous owner fix the wrong thing and create a new series of problems. It went like this:

1. saucer switch was apparently a littlle bent out of shape, therefore the saucer did not work.
2. the guy deduced it was a faulty coil, so he replaced it with a completely incorrect coil. Instead of being a Bally 3 lug, 2 diode coil, he put in a Williams 2 lug, 1 diode coil. This sent crosstalk voltage to other coils in the same circuit.
3. The coils in this circuit are on the solenoid expander board. This board looked like it had been worked on several times before, meaning someone already had doubts about it.
4. When I clipped off the incorrect saucer coil and booted the machine, the expander board made a loud buzzing noise as if it's relay was not working correctly.

So my solution was to install the correct, 3 lug, 2 doide Bally saucer coil AND to replace the buzzing, hacked solenoid expander board with a new one. $55 later, everything works perfectly. Did not have to go through the machine and check / replace every diode, thank God.

My learning experience from this is on Medusa, you have all the drop target coils, the knocker, the ball launcher, and the saucer coil all on the solenoid expander board. This in turn actually runs from an SCR on the lamp driver board instead of the usual solenoid driver board. If any one of these coils is malfunctioning due to a bad diode or short, or if the little Solenoid expander board is not working (with its little light bulb) then multiple problems can show up including incorrect resetting of the drop targets and failure of the ball to launch.

Shesh! All starting because a saucer switch was not adjusted correctly, per point 1. as stated above!! (incorrect saucer coil pictured below)

Photo Feb 25, 6 59 03 PM (resized).jpg

3 months later
#11 2 years ago

Okay, problem finally solved. After trying everything, I eventually hired a professional pinball repair guy who solved the problem in about an hour. So in summary: Auxiliary coil circuit with the drop target coils, knocker, saucer, and ball launch were acting flaky or not working intermittently....

- pulled every coil and checked it
- replaced every diode on every coil in this circuit of coils, even though they all tested good
- replaced the auxiliary coil driver board with a brand new one
- replaced the lamp driver board with a new one (it drives the aux coil board)
- also replaced the auxiliary lamp driver board while I was at it
- replaced the the entire MPU board with a new one
- replaced the rectifier board with a new one - it was a little toasty anyhow
- sent out the power driver board and sound board out for professional testing and refurb

Problem still remained. And the final culprit... a poorly repinned molex connector on the J4 connector of the power driver board! There were two little wires shorted and almost touching, looking even a little burned. Also reflowed the header for J4.

Well, I learned a lot and now I have all these great new parts in my machine! But I spent hundreds of dollars and wasted weeks of time trying to figure this out. I am posting this on the Medusa forum so hopefully someone else can solve their problems quicker than me!

IMG_1243 (resized).JPG

#12 2 years ago
Quoted from calico1997:

Got my problem solved with the help of Toyguy and Pinwiki. Basically one simple problem apparently caused the previous owner fix the wrong thing and create a new series of problems. It went like this:
1. saucer switch was apparently a littlle bent out of shape, therefore the saucer did not work.
2. the guy deduced it was a faulty coil, so he replaced it with a completely incorrect coil. Instead of being a Bally 3 lug, 2 diode coil, he put in a Williams 2 lug, 1 diode coil. This sent crosstalk voltage to other coils in the same circuit.
3. The coils in this circuit are on the solenoid expander board. This board looked like it had been worked on several times before, meaning someone already had doubts about it.
4. When I clipped off the incorrect saucer coil and booted the machine, the expander board made a loud buzzing noise as if it's relay was not working correctly.
So my solution was to install the correct, 3 lug, 2 doide Bally saucer coil AND to replace the buzzing, hacked solenoid expander board with a new one. $55 later, everything works perfectly. Did not have to go through the machine and check / replace every diode, thank God.
My learning experience from this is on Medusa, you have all the drop target coils, the knocker, the ball launcher, and the saucer coil all on the solenoid expander board. This in turn actually runs from an SCR on the lamp driver board instead of the usual solenoid driver board. If any one of these coils is malfunctioning due to a bad diode or short, or if the little Solenoid expander board is not working (with its little light bulb) then multiple problems can show up including incorrect resetting of the drop targets and failure of the ball to launch.
Shesh! All starting because a saucer switch was not adjusted correctly, per point 1. as stated above!! (incorrect saucer coil pictured below)

Yikes, maybe clip your coil wires closer to the lug next time. You're gonna run out of harness.

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