Centaur II - Transistor keeps blowing

[Vengeance]

So I have still yet to play a full game on my restored CII since I finished it, I keep having problems with a single transistor.

It's the transistor associated with the auto launch coil.

I replace the transistor, it works for about 10 - 20 pulls, and then stops working again.

The coil doesn't lock on, or fry, or anything, it works normally and then stops. No indication other then the balls stop launching.

I don't have a spare coil to test if it is the coil or not, but I replaced the diode on the coil and that didn't change anything.

Any thoughts on what the issue could be.

I'm guessing the coil but figured I would see if anyone else had any ideas.

 

[g-man]

If you are like me, you are waiting for Menace, Cooke or the kingpin Sylvain to come to the rescue.

However, while we wait, I will throw a couple of things out there ~ neither of which will probably help. :FP:

First, I'm wondering if the resistor associated with that transistor might be failing and thus allowing the transistor to blow.

Second ~ and this is really an additional question that I have about that specific coil ~ I have read that the autokick coil is supposed to have two diodes on it ~ one for the coil and between the incoming power and the power lug. Mine does not and it appears yours does not either. My machine works fine without it and yours seems to as well. Is the two diode thing a myth ? Is it just for Centaur and not C2 ?

Anyway, I suppose the coil could have a short in it that is so minute that it doesn't affect operation until the windings get a little warm with use. Or, although you said the coil does not lock up, could the plunger be binding every once in a while ?

Question: When the transistor finally blows, is it after the autokick has sent several balls up the playfield ?

 

[sylvain]

Is the transistor opening or shorting after these 10-20 operations ?
Sometimes the diode on the Solenoid Driver board, driving the base of the drive transistor, can go intermittent.

Also make sure the coil is the proper number (not an incorrect replacement), and measure its resistance to make sure
the coil is not partially shorted causing issues with the transistor after while.

- Sylvain.

 

[Vengeance]

I don't know the difference between shorting and opening.

The auto kicker works and then stops working.

I can't find the list of solonoids in the manual online to verify I have the correct soloniod, but the auto kicker worked fine without issue ever before I did my restore and has only stopped working after I finished the restore.

I'll check the resistance on the coil and get back to you

 

[g-man]

I don't know the difference between shorting and opening.

I can't find the list of solonoids in the manual online to verify I have the correct solenoid

Auotkicker ( kick to playfield ) is AO-35-950. There is only one of these in the game.

If "open", I think the voltage readings should be zero. But I dunno.

 

[Vengeance]

Ok back at this.

I checked the ohms on tho coil it is at 6ohms, pinrepair says between 3 - 11 is fine

I checked for voltage and I have 44 volts at the coil

The coil number is different then the one Glenn said though

I have an AO- 25-950

Glenn can you confirm its 35 and not 25?

Any other thoughts?

 

[g-man]

Hey Adam.

Well, isn't THIS embarrassing. The manual does say "25" not "35"....sorry 'bout that. Mine is also a 25.

Did you replace the associated diode and resistor on the SDB ? Did you replace the diode on the coil itself ?

I wonder if the expander board relay is sticking / arcing ?

Funny, I have read that the kick to pf coil was supposed to have 2 diodes, but mine doesn't and apparently yours doesn't either so that may also be a myth. Mind you, if your coil was not blowing transistors before, then there is no need to suspect that now.

I will keep researching the problem. Lemme know how you make out.

 

[Vengeance]

No I haven't replaced the diode and resistor associated with the transistor, Ill try that nexy I guess.

I may try taking the Sdb out of my flash gordon and give it a try and see what happens.

Thanks for the verification Glenn

Adam

 

[sylvain]

Yes, the coil resistance for a 25-950 should be around 6.5 ohms.
Have you replaced the diode across the coil lugs yet ?

Also - Is the coil running hot after a while even if not activated ?
Is the pre-driver transistor in the chip (CA3081) and associated 120 ohms resistor good ?
(in addition to the 1N4004 diode and 330 ohms resistor associated to that transistor on the Solenoid Driver board)

Good luck!
- Sylvain.

 

[Vengeance]

Finally!!

Finally figured it out, I haven't played a game of Centaur since February 2012.

After putting in the Flash Gordon SDB and still having the same problem, I figured there had to be something else in the chain.

So I started to look around, and decided to take a look at the Solonoid Expander board. There is one that is hooked up to the coil for the launcher.

I figured I would try and refolw all the solder on the board and see what happens, I did that and the coil locked on, looked at the board and saw I had connected to points together on the board with solder by accident, but figured that was a change in behavior so good. Fixed that up and then tried it again, and it worked!! So I screwed the board back onto the PF and it stopped, WTF!!

Took it off and it started working again!

God dammit what is going on!

Played around with it a bit and figured, must be the connector, so changed the connector on the SEB and SUCCESS!

I hate these stupid intermittent problems, all these false positives, coil doesn't work, change transistor, coil works, then after a few pulls stops again, change transistor works again, then stops again. Man annoying as hell but glad it's figured out now

 

[WARLOCK]

Congrats Adam. Tricky problem.
In the AV production business, we always say "it's a cable"! (or a connector)
90 % of the time, that is the case.
Enjoy!

 

[spiroagnew]

Glad to see it all worked out, enjoyed following the progress...have fun with the game!

 

[Chris Bardon]

Glad you found it-intermittent problems are the worst, especially since you never quite know if it's really fixed or not.