(Topic ID: 94446)

Medusa strange goings on

By Validpowerdetect

6 years ago

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  • 9 posts
  • 4 Pinsiders participating
  • Latest reply 3 years ago by thierryv
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#1 6 years ago

My Medusa is acting strangely. When the leftside target switches, plust the right side drop targets are hit, the knocker goes off, the upper flippers jump, the voice laughs. Probably of couple other solenoids go off too, but a lot is happening at once.

Self test solenoid, switch, lamp tests are all OK
SDB swapped out, no effect
MPU board swapped out, no effect
Sol Exp swapped out, no effect.

Worked perfectly before I changed some dip sw settings to Lib, but I have changes those back, plus used a different MPU. I have not used different ROMS.
Whats up?

#2 6 years ago

Did you change any rubbers or clean the playfield?
Check to make sure no switches are close to touching and the vibration is setting things off.

Did you also change any bulbs under the playfield?
Go back under and make sure nothings touching.
Tons of stuff to short to the GI on medusa.

Also the 0.5 mfd capacitors on the pop switches and other quick action switches (if they are still there, sometimes cut off)
If there are any capacitors on the switches try cutting off one leg. The machine will work fine without them. But you can replace them when you get a chance if this is the problem.

When the caps go bad wierd things happen. Could be the problem if its not closed switch vibration because of new rubbers.

Bad switch caps wont show up in solenoid test. Only while playing.

#3 6 years ago

It also exhibits these symptoms upon starting a game, i.e. the knocker, the zipper flippers, the laugh, etc

#4 6 years ago

Since the sound board shares the encoded solenoid signals, unplug the sound board and see if symptoms changes.

Otherwise put the game in solenoid test, take note of any solenoid firing out of order. Sounds like you have encoded solenoid data issue(typically an open line).

#5 6 years ago
Quoted from Validpowerdetect:

It also exhibits these symptoms upon starting a game, i.e. the knocker, the zipper flippers, the laugh, etc

Does it do it as soon as a ball kicks into the shooter lane when you press start.
The ball trough solenoid is fireing and causing either vibration triggering switches. Or the caps. Or a lampsocket is touching something it shouldnt.

Start with simpelest to check and work up to the more difficult things to troubleshoot.

#6 6 years ago

This problem is still kicking my ass. What I do know: 1. When I force the Sol Exp relay to energize, I still have power on the coils the are supposed to be de-energized, i.e. the knocker, and some drop tgt resets. I confirmed this with a meter.
It's not the sol exp board. Moved it to 8BD, works fine.
What I believe is going on: There is a shorted diode some where, backfeeding the system.

#7 6 years ago

Check.all.your lamp sockets etc. Make sure nothing is touching. And make sure nothing is touching any of the switches. There is so much going on under medusa that its possible a lamp socket is causing a short to a switch, a coil. Or any of the wires might be touching something. Etc, etc.

Check the simple stuff first. And check those caps on the switches or cut them all off. One bad switch capacitor will.cause havok to early bally games,

Medusa, motordome, fireball classic, escape from the lost world. Etc. All have this problem, and the caps cause the symptoms you are describing.

The caps are leaking so they show good in switch test. But in a game they momentarly short and cause coils and switches to register.
Cut one side off of all of them, check the coindoor, slamtilt, tilt too. The game will still work. Then replace them if it fixes the problem.

1 week later
#8 6 years ago

Back to working this problem after a week of fishing in AK.
Should not the voltage on a coil on the n/c side of the sol exp drop to 0v when it is active (energized).
On mine, the knocker increases to 57-62v during that part of the sol test that the sol exp is servicing the n/o set of coils.
BTW, caught lots of fish!

3 years later
#9 3 years ago

Did you ever find the culprit , because my medusa has the same problem .

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