Tech: Whirlwind Stuck on Coil

wxforecaster

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I inherited a Whirlwind project with a multitude of problems (enough electrical tape to bound a small child). I'm certainly not a skilled person by any means, but I've repaired everything on the machine from spliced wiring to burnt connectors and so on.

I'm "stuck" with one last issue - a pesky right sling shot that fires as soon as you turn on the game.

When I pull the J7 connector from the driver board and the coil stops...so that's a good sign.

I tested U45 and all the pins (non-power/ground) are correctly between .4 and .6V. Other solenoids driven by U45 are also working correctly. So, before I go ahead and replace Q69 and Q68 transistors, I did happen to notice that the wiring to the coil lugs is reversed from another game I had. The problem child slingshot has the thick purple wires on the left lug and the blue/yellow thin wire on the right lug. My working example has these flipped.

I can't see *why* this would matter on such a 2 lug coil with no diodes, but I figured I'd ask first. I also noticed that the coil that's in there is a AE-26-1200 as opposed to the original AE-26-1500. Again, I don't think there's a problem here, but I'll let the experts chime in.

Thanks in advance,
Evan
 
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I inherited a Whirlwind project with a multitude of problems (enough electrical tape to bound a small child). I'm certainly not a skilled person by any means, but I've repaired everything on the machine from spliced wiring to burnt connectors and so on.

I'm "stuck" with one last issue - a pesky right sling shot that fires as soon as you turn on the game.

When I pull the J7 connector from the driver board and the coil stops...so that's a good sign.

I tested U45 and all the pins (non-power/ground) are correctly between .4 and .6V. Other solenoids driven by U45 are also working correctly. So, before I go ahead and replace Q69 and Q68 transistors, I did happen to notice that the wiring to the coil lugs is reversed from another game I had. The problem child slingshot has the thick purple wires on the left lug and the blue/yellow thin wire on the right lug. My working example has these flipped.

I can't see *why* this would matter on such a 2 lug coil with no diodes, but I figured I'd ask first. I also noticed that the coil that's in there is a AE-26-1200 as opposed to the original AE-26-1500. Again, I don't think there's a problem here, but I'll let the experts chime in.

Thanks in advance,
Evan

Evan: The "no-diode/two lug issue/reverse wiring" is OK. The different coil >does< concern me, I had a problem like this recently, tried a coil with a very similar number and it got HOT. THAT could be what has happened, it has drawn too much current from the driver transistors, heated up, and shorted them.

Always err on the side of proper coil number FIRST, then go ahead and replace your transistors. If you do your transistors first the coil >may< work, for a short time - hard to say.

Chris
 
Have you checked the transistor that drives it ?

From what you describe about no diode, and coil number. These won't matter. Won't cause the coil to lock on.

The 1200 will be stronger.

LTG :)
 
Sigh...after tackling this for the past hour, I have gotten no where.

I replaced the AE-26-1200 with a brand new AE-26-1500 just to make sure the coil wasn't the problem and both slings had the same power.

I replaced the TIP102 at Q69 and the 2n4401 at Q68.

Both tested good in and out of circuit and all voltage/continuity tests are good. Tested U45 and all legs are between 0.4 and 0.6V.

Powered the game on. Right sling instantly fires on. Game has no other problems.

If I pull the J7 connector on the driver board, the sling coil lets go. <-- wasn't it correct to assume based on this that the problem is a pre-driver transistor problem?

Evan
 
I inherited a Whirlwind project with a multitude of problems (enough electrical tape to bound a small child). I'm certainly not a skilled person by any means, but I've repaired everything on the machine from spliced wiring to burnt connectors and so on.

I'm "stuck" with one last issue - a pesky right sling shot that fires as soon as you turn on the game.

When I pull the J7 connector from the driver board and the coil stops...so that's a good sign.

I tested U45 and all the pins (non-power/ground) are correctly between .4 and .6V. Other solenoids driven by U45 are also working correctly. So, before I go ahead and replace Q69 and Q68 transistors, I did happen to notice that the wiring to the coil lugs is reversed from another game I had. The problem child slingshot has the thick purple wires on the left lug and the blue/yellow thin wire on the right lug. My working example has these flipped.

I can't see *why* this would matter on such a 2 lug coil with no diodes, but I figured I'd ask first. I also noticed that the coil that's in there is a AE-26-1200 as opposed to the original AE-26-1500. Again, I don't think there's a problem here, but I'll let the experts chime in.

Thanks in advance,
Evan

It is possible that a chip further upstream is bad. I do not have a manual near me. It may have gone to the 6821. You will need a schematic. Pre driver most likel y shot prior.
Evan[/QUOTE]
 
OK, here's some other oddities that may help finally solve this puzzle.
When I pulled J7, the coil let go. However, when I pull 1P19 from the main board, the coil still holds, which the schematics show is the terminus of the blue/yellow wire.

With the game powered off I did a resistance test from ground to both coil lugs.

On the left (good) sling, I get 17.5 ohms to the violet/yellow wires, and 32 ohms to the blue/red wire.
On the right (bad) sling, I get 17.5 ohms to the violet/yellow wires, but only 3 ohms to the blue/yellow wire.

Even more baffling is that a friend tested this on a known working Whirlwind and got 3.3 KILO ohms on all 4 lugs (2 on each sling).

I would expect to see an identical match here, no? I'm beginning to wonder if my blue/yellow wire is somehow grounded somewhere else (causing the coil to lock on), but would rather get some thoughts from the experts here before I true to track this wire back through all the tight wire bundles.

Evan
 
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It is possible that a chip further upstream is bad. I do not have a manual near me. It may have gone to the 6821. You will need a schematic. Pre driver most likel y shot prior.
Evan
[/QUOTE]

+1, I think you are getting into a logic problem at this point. IIRC, it goes coil/driver/predriver/TTL (usually a 7408)/6821. It will probably be the TTL before the predriver (possibly a 7408).

Chris
 
The U45 chip if I recall is a 7402. Is this the last step upstream? The system11 pinrepair manuals I had printed out way back when really only discuss the TIP102 (driver) and 2n4401 (predriver) for locked on coils.

And where can I get a few?
 
OK, here's some other oddities that may help finally solve this puzzle.
When I pulled J7, the coil let go. However, when I pull 1P19 from the main board, the coil still holds, which the schematics show is the terminus of the blue/yellow wire.

With the game powered off I did a resistance test from ground to both coil lugs.

On the left (good) sling, I get 17.5 ohms to the violet/yellow wires, and 32 ohms to the blue/red wire.
On the right (bad) sling, I get 17.5 ohms to the violet/yellow wires, but only 3 ohms to the blue/yellow wire.

Even more baffling is that a friend tested this on a known working Whirlwind and got 3.3 KILO ohms on all 4 lugs (2 on each sling).

I would expect to see an identical match here, no? I'm beginning to wonder if my blue/yellow wire is somehow grounded somewhere else (causing the coil to lock on), but would rather get some thoughts from the experts here before I true to track this wire back through all the tight wire bundles.

Evan


The left/right ohms wont be of that much use unless you are certain the circuit from ground to the resistor is the same on both sides. Just measure the individualresistor to make sure they are within specs.

If you are measuring ohms at the lugs you will get very different readings because you will get resistance from the coil itself. Thats alot of wire in there!
 
OK, so I decided to follow the wires for this coil and stumbled onto something VERY interesting.

The blue/yellow wire on the sling coil lug goes to pin #5 on J7 on the driver board. From there, it passes through a TIP36 at Q8 and onto pin #4 on J3 on the driver board. That connector is then wired to 1P19, pin 7 on the main board.

What I found is that the TIP36 at Q8 is bad! (outer legs run 0V instead of between .4 and .6V like the other TIP36s). Sigh. Apparently, either I misread the repair manuals and help offerings here, but was focused on the pre-driver instead of the actual drive. Perhaps that's what Lloyd was trying to tell me initially!). It never dawned on me to check anything on this board, but alas I'm a noob who wasted a few TIP102s and 2n4401s for nothing more than soldering practice and the fun of pulling/replacing umpteen connectors to get the system 11b board out of the game 4 times :)

This explains why the coil still had power when I pulled 1P19 and why the 7402, TIP102 and 2n4401 all tested good before and after replacement. They weren't even part of the problem. The TIP36 was completing the circuit all itself.

UPDATE: Replaced TIP36 at Q8 on the driver board. Turned on the game. I have a working Whirlwind.
Un-fracking-believable. Interestingly, the pinrepair guides for the WPC games seem to more directly allude to the TIP36 prior to replacing the predriver transistors than mere glossing this was given in the system 11 repair guide.

Case closed.

Evan
 
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Don't feel bad. I just went through the same scenario with a DE game. Stupid coil locked on, blew the fuse. Instantly replaced the TIP and pre driver and same damn issue. Not to mention I tested the old components which tested good. I'm not real great at schematics but I tested everything else (resistors, coil) and it all tested good. Out of frustration I decided to pull the power board and look at what the blowing fuse was tied into and low and behold - a bad TIP 36C. Gah, all that freaking work to find out the problem was on another board all together. It's just a common knee jerk response to replace the TIP102 and pre driver because that's usually what blows when a coil locks on.

Lesson learned.
 
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