Intermittent magnet strength issue

[cooldan]

the magnet on my Rollergames tries to catch the ball every time (i can see the ball slow right down) but only actually manages to catch and hold the ball about one time in three. what could cause this, any ideas? what are the options?

Stormy had a quick look, and ground the magnet end down in case it was caused by mushrooming of the end, or something, but no fix.

Magnet coil checked against the manual, and it's the correct type (B-13522, fact fans).

Position-wise it's perfect, it's flush with the playfield and can't go any higher.

so could it be the board, the magnet, or the wires in between? on the board, i've tested the driver transistor and the predriver transistor, and both test fine. i wondered about intermittent problems with power to the coil, but it works fine in coil test, and as i say, you can see it trying every time, so it's getting juice. not sure if it's enough juice though - it was suggested to me that i check how consistent is the power from the transformer, but that is off my map regarding knowledge and experience to date.

so what do i test, and how and where?
i don't want to buy a new magnet/coil if it's not needed, but will do if that will fix it. i don't have another one i could try out, sadly.

any and all help gratefully received

 

[Rus121]

Windings in the coil weakened?

 

[Moonraker]

Don't know enough about the game but I'd have a look at the ball detection which activates the magnet, persumably a switch somewhere which may not be responding quick enough so the magnet is activating just a tad too late to hold sufficiently...

 

[cooldan]

cheers Russ, cheers Pete, both good ideas that i will explore:

i don't think the coil is the problem, as when it works, it works with a powerful ptwang! but i don't know what i'm looking for, as i've never seen a coil with a strand unwound or weakened or whatever, so i could be talking outta my ringpiece as usual

i *think* the magnet is activated by the CPU at the same time as firing the pit coil to send the ball over towards it (only when magnet has been activated hitting the left side SKATE standup targets. otherwise the pit coil sends it over but magnet is not on duty). the only switch there is the one in the pit that tells the pit coil to fire, so i'm presuming that if the ball is sent over at all, it should be on time. but i like the idea of it being a half second or whatever too late. maybe there could be a delay caused by another method?

:blah::blah::blah::blah::blah::blah::blah::blah::blah: i think i might ramble a bit now (for a change)

so GrizZ sent me over this fascinating link that had all sorts of fresh ideas in it - https://groups.google.com/forum/?fromgroups=#!topic/rec.games.pinball/3SZBB36_XC4 - fresh to me anyway. i hadn't even realised there was another transistor to test, so i tested the TIP36C on the high current driver assembly, hoping for a fault. it tested fine, as did the diode on the little board.








so now i'm running through the list of possible causes, and i've collected these:
1) a 'weak trace' on the board (!) to be explored by trying to attach a jumper (!!) from one of the magnet transistors to it's destination. sounds very complex and a bit beyond my knowledge still, but i'll have a go if all else fails and if someone walks me through it. i already tested predrive transistor 2N4401 at Q78, and it passed. and i already tested driver transistor TIP122 at Q79 and that passed too.

2) something wrong with the (female) connectors or the (male) header pins on one of the boards: manual tells me that J19 pin 9 on the CPU board is the original source, and that J3-1 and J7-1 on the auxiliary power driver board are also in the mix. plus i now also know about connectors J1 and J2 on the little high current driver assembly thingy. that gives me loads of possible things to try - i can change a simple female IDC connector, but i haven't done male header pins before, those ones on the board itself are still a bit beyond me til i get my board soldering skills refined.

3) the magnet itself - i already checked that the coil is the right type (or at least the coil wrapper says it is!) but know nothing about the insides. magnets, it appears, have this funny thing in the middle of them. i can move it up and down, and i'm happy that the vertical position is now optimum, but the coil itself still has a fair bit of sideways wiggle around it, is this normal? then this ideal "golf-tee shape" i read about, what is that? i know that Stormy already filed it down, but it doesn't look anything like a golf tee to me. does anyone know if i should try to attack it some more?

4) that new idea from Ive's RGP link - put in an extra ground wire from that high current driver assembly board. sounds logical, so i think i'll try that first - but help me check what i'm doing here? according to this 'schematic' (!!!! i've never looked at one before so bear with me) i think it says that ground is pins 1 and 2 from J1. which seems to be reflected by the printing on the actual board itself where it says GND.



but if you look again at the first pic in this post, the one with the little board in situ, it seems there are already two wires in the bottom two pins of the connector (or actually one, circled round upon itself). so am i right in thinking that i just have to drag out that useless loop on pin 1 of J1, and in it's place i attach a wire connecting pin 1 to a nice stable earth? if i got that right, can someone suggest a convenient place to earth it to, other than the cabinet braid?

i'm getting a headache from all this thinking, i need some booze.

but first, in all this excitement i have forgotten if i have posted 8 pics or only 7. well to tell you the truth, i've forgotten myself. so do you feel lucky, punk?

























BOOM

 

[Sgt GrizZ]

I think the gist of The Korns post was that somewhere in the whole magnet chain current was being lost.

Regarding yr Q's

1.Basically jumpering/lead with clips between components etc to see if it improves things. If so then may indicate a flaky trace (?) on the board

2. Header pins - check visually for broken/cracked solder. Buzz them out to check for good continuity. Reflow solder anyway to be sure if you want.

3. 'golf tee shape' - I think by this he means somehow making it slightly 'cupped' /concave so the ball maybe more likely to sit on it. Not sure about this myself ...to be effective wouldn't this surely interfere with ball movement ??? Unless I'm misunderstanding.

4. Correct those are the ground connection. I would just try and attach another wire to the connector and to ground braid for now and see if it helps in anyway, Korn seemed to think it did, use croc clip or whatever you can that works. If it does then you can work out a neater solution.

 

[ronsplooter]

Re: point 3 ,the magnet, I'm assuming the bit in the middle of the steel bar is the iron core and maybe the golf tee shape refers to the shape of the magnetic field generated out of the top rather than the shape of the bit of metal?

http://en.wikipedia.org/wiki/Electromagnet

Have you tried measuring the current supplied to the magnet from the point the ball drops into the pit until it gets kicked across and reaches the magnet. This should give you an idea as to whether the magnet is getting the correct amount of current to activate with sufficient power and also test whether its getting the current at the right time to activate and hold the ball. Then try doing this test a few time to see if the behaviour is consistent or not. Apologies if you've already done this dude, just came into my brain when reading your last post and I didn't check back through the thread.

How does this magnet work? When it does grab the ball so you can hit it up the ramp with the flipper does it hold it indefinitely and the strength of the flipper hit breaks the magnetic bond or does it release it just as you flip so that the flipper doesn't have to overcome the magnet?

 

[Sgt GrizZ]

Re: point 3 ,the magnet, I'm assuming the bit in the middle of the steel bar is the iron core and maybe the golf tee shape refers to the shape of the magnetic field generated out of the top rather than the shape of the bit of metal?

http://en.wikipedia.org/wiki/Electromagnet

Hmmm...but how on earth do you 'see' the shape of the magnetic field ??? I'm pretty sure in the rgp post Korn is actually referring to the physical shape.

 

[ronsplooter]

Hmmm...but how on earth do you 'see' the shape of the magnetic field ???

Good point, in my defence I have been drinking this evening

 

[Sgt GrizZ]

Good point, in my defence I have been drinking this evening

Good man, Sgt GrizZ salutes ....makes me feel better about this large nightcap I just poured myself :smokin:

 

[cooldan]

Have you tried measuring the current supplied to the magnet from the point the ball drops into the pit until it gets kicked across and reaches the magnet. This should give you an idea as to whether the magnet is getting the correct amount of current to activate with sufficient power and also test whether its getting the current at the right time to activate and hold the ball. Then try doing this test a few time to see if the behaviour is consistent or not. Apologies if you've already done this dude, just came into my brain when reading your last post and I didn't check back through the thread.

no, i haven't, and that sounds like a good idea now that i have my schmancy multimeter. where do i put the red and black leads? any idea what kind of numbers i'm looking for? any dangerous pitfalls i need to avoid? i'll obviously have to do it with the playfield up, so presumably i need to somehow start a game and manually trigger the pit ...... hmmmm......

How does this magnet work? When it does grab the ball so you can hit it up the ramp with the flipper does it hold it indefinitely and the strength of the flipper hit breaks the magnetic bond or does it release it just as you flip so that the flipper doesn't have to overcome the magnet?

nope, not indefinitely. from the rulesheet (here http://pinball.org/rules/rollergames.html) - "The Magnet gives you a little bit of assistance in shooting the Wall. When the Magnet light at the Pit is lit, shooting the Pit activates the Magnet, which is at the tip of the upper right flipper. Here's the sequence of events: The screen shows "Don't flip" and the announcer says "Don't flip" as the ball rolls along the habitrail. The screen then counts down "Three--Two--One," estimating the time until the ball will come to rest on the magnet. After the countdown, the screen says (and the announcer yells) "Flip," by which time the ball should be at rest on the magnet (although I have seen games where the magnet was too weak to catch the ball). If the ball stops early, go ahead and flip; the game won't mind if you don't wait.If you flip too early, the magnet will turn off immediately, so don't do it! It will also turn off if you wait too long after being ordered to "Flip!" If something goes wrong with the magnet or the Pit kicker, you're outta luck. The game will continue on as if everything were OK, and you'll lose the chance at the easy ramp shot."
.....this doesn't answer the question though, does it? whether the magnet is turned off by the action of the top flipper? i dunno, i suppose so. that would make sense, but i haven't looked for or seen it specifically written anywhere in the manual.


i'll get down to the Tiki Hut and try the trick with the doubled up ground wire as soon as the plumber leaves. hope to be able to report back to the group with my findings soon - but i also want to be able to learn a new trick by doing that current testing thing you mentioned.

 

[ronsplooter]

If you flip too early, the magnet will turn off immediately, so don't do it! It will also turn off if you wait too long

That quote would seem to suggest that the magnet is turned off by the flipper press or after a certain time has expired if you don't flip. Killing the magnet when the flipper is pressed would make sense as then the flipper doesn't have to fight the magnet and you get the full power into the shot up the ramp. Anyone else able to confirm this?

Re: measuring the current at the coil, if you've got croc clips for your multi meter then maybe you could attach it using those so you've got your hands free to operate the game?

 

[cooldan]

problem more or less fixed - by tightening the coil around the magnet, and readjusting the delivery angle of the ball from the pit, i got it catching the ball most of the time. by checking the current in real time as suggested, i realised that the inherent timing is off, the CPU turns the magnet on a shade late, so i can improve this by delaying the ball a second or so by bending the tab at the bottom of the wireform ramp from the pit.

details in original shop log here - http://www.pinballinfo.com/forum/sh...ergames-shop-log&p=21523&viewfull=1#post21523