Comet repair job

[Lindsey]

...but since you said it, I suppose I'll test it now. Damn you Lindsey.

haha

Well... if you're going to go to the trouble to make a thread and intend that it be used as a repair reference in the future you should try to add information that might actually be useful. We already have enough "I made this guess then threw these parts at the game and it works! Look how awesome I am!" threads. Guesses and assumptions are useless in this context.

If you're going to demonstrate a repair, even if it was a guess that led you there, you should explain why that was the problem and what led you to that conclusion. In gory technical detail. At least that's my opinion

FWIW: I wouldn't paint masking tape. It will flake off instantly and make a hell of a mess.

EDIT: 7000th post... whoopie...

 

[shardian]

It was bad. Moot point though, because there was so much damage from that cooked coil that it had to have been stressed even if it had passed. I was replacing it either way.

 

[Lindsey]

It was bad. Moot point though, because there was so much damage from that cooked coil that it had to have been stressed even if it had passed. I was replacing it either way.

Not so much "your bad". Believe it or not I'm actually trying to help you learn something.

How is a cooked coil going to put stress on the switching logic behind the pre-driver transistor? That's not a rhetorical question. I'm seriously wondering.

EDIT: My theory is that this whole problem was caused by a pop bumper switch sticking closed. Possible because the skirt got stuck.

 

[shardian]

Not so much "your bad". Believe it or not I'm actually trying to help you learn something.

How is a cooked coil going to put stress on the switching logic behind the pre-driver transistor? That's not a rhetorical question. I'm seriously wondering.

EDIT: My theory is that this whole problem was caused by a pop bumper switch sticking closed. Possible because the skirt got stuck.

It could be that. Either way the circuit was overfused, so it just kept burning and burning at the coil and at the board.
How could the logic chip get fried? I'd assume the oversize fuse has a big part to blame in that. With a normal fuse, the fuse will pop hopefully before too many of the failsafe components fry before the short works its way back to logic.

Such as in this case, where the fuse didn't pop and the board literally started burning. The resistors above the tip102 are black from smoke/heat.

I know you are trying to help. My time is money on this one though, so I don't want to waste time. I know some of you pro's know the routine for testing a 7408 off the top of your head, but I don't I'd have to go look at a schematic, do a bit of research, etc. I save that for when I have to do it. If I didn't already have the chip on hand, I would have tested without question. If there wasn't a socket already there, I would have tested without question.
Do you see where I'm coming from in this case?

 

[Lindsey]

It could be that. Either way the circuit was overfused, so it just kept burning and burning at the coil and at the board.

"either way" is debatable. I still like my theory. hehe

How could the logic chip get fried? I'd assume the oversize fuse has a big part to blame in that. With a normal fuse, the fuse will pop hopefully before too many of the failsafe components fry before the short works its way back to logic.

Such as in this case, where the fuse didn't pop and the board literally started burning. The resistors above the tip102 are black from smoke/heat.

I know you are trying to help. My time is money on this one though, so I don't want to waste time. I know some of you pro's know the routine for testing a 7408 off the top of your head, but I don't I'd have to go look at a schematic, do a bit of research, etc. I save that for when I have to do it. If I didn't already have the chip on hand, I would have tested without question. If there wasn't a socket already there, I would have tested without question.
Do you see where I'm coming from in this case?

I see where you're coming from. I'm still going to break your balls. Call it tough love if you want

So... were both of the transistors shorted?

 

[Tim N.]

Okay I took plenty of pics for you guys. Up first are the playfield before shots. You can see where the playfield is horribly stress cracked in the clear and paint. Nothing can really be done about this. Also you can see the fading of the non-mylar areas. Other than that, there really isn't much wear. This playfield will be a great test for the treasure cove kit. If this turns out well in the hour or so I will spend on it, I think treasure cove will owe me a few free replacement spplicators. Why? Because surely many of you will rush to get the kit!

The mylar area will look great, and the kit should take out a lot of the ball swirl. The thing I am worried about is removing paint. I'll have to take it easy in those areas.

I am not doing a complete tear down on this one. Just a basic cleaning and a polish with the cove kit. No removing/polishing of any playfield parts. Well I will clean the main ramp, but that is about it. I will be putting on all new target decals, and a flipper rebuild. The left flipper has the fatigue flutter, but the right one is fine. I've always wanted to try a rebuild kit, and what better time to try it than on someone else's dime.

Good luck with the TC kit..... I would highly recommend staying away from any non-mylar areas with it. It will burn through those areas very quickly (I believe TC even has a disclaimer about non-cleared PFs).

Probably just a quick Iso alcohol/Magic Eraser treatment (again carefully) in the swirl area. Without some sort of protectant, those swirl areas will dirty fairly quickly again as your new clean wax turns into older, dirty wax.

Good luck, looks like a fairly decent Comet. I was actually expecting a lot worse....

 

[shardian]

So... were both of the transistors shorted?

I thought I said that already? Both were shorted on and burned up. Knowing that for sure now, do you see my side?

 

[Lindsey]

I thought I said that already?

Nope.

Both were shorted on and burned up.

Just checking. I'm not sure that you explicitly said they were shorted.

EDIT: Nope

 

[shardian]

I thought I said that already? Both were shorted on and burned up. Knowing that for sure now, do you see my side?

Oh, and the 102's case was cracked in half to give you a 'battle damage' reference.

 

[ixtlann]

i miss my comet pin

 

[shardian]

Good guess Lindsey - the culprit was a sticking switch. The skirt activator was getting stuck in the switch cup. I polished the cup and replaced the skirt.

Everything play wise is working now. Replaced both bad coils, replaced a bad flipper button switch, fixed the lane change switch...I think that is everything. Now I am replacing every bulb in the game with new #47's. I'm also replacing all of the flashlamps just for posterity sake. A handful are out, but there is only like 12 in the game. Might as well minimize maintenance with a dollar's worth of parts.

 

[shardian]

Okay, here is another problem I found - the speech is messed up. I posted this over at RGP and have gotten nothing so far. Here it is copy/paste style:

I am working on a Comet with a Speech issue. I'll summarize what it
has done so far:

-Initially, there was sound present during speech, but it was super
garbled. I reseated the speech roms and the CPU sound rom. At this
point about half the speech sounds were audible, but very faint.
- I pulled the speech board for inspection. U3's legs looked pretty
cruddy, so I reflowed the solder on it. Upon reinstalling the board, I
had all speech when the speech swtich was pressed on the CPU. I
started a game and the speech worked for about a minute. Nothing I did
made it better.
-The next day I came back to it, and completely resoldered U2 and U3,
including making sure the 2 top-side trace connected legs had good
connection. Plugged it back in and speech worked again. I played a
whole game just fine. Came back in the morning to see if it played
cold. It did not- speech was gone.
- Since heat seemed to have something to do with it, I used a heat gun
to warm up U3. After turning the game on, only garbled static came
out. during speech test.
- At this point I suspected U3 was bad. It was the only thing I was
messing with and it brought full functionality back. I ordered the
amps and caps since I would have it out anyways. I started by only
replacing U3. Put it in a everything worked same as the last two times
I messed with U3. After about five minutes, it was all gone again. I
proceeded to replace U2 and all caps but the polystyrenes. Now I have
nothing at all.

At this point, I assume U1 is bad. Figured I'd post here though and
see if anyone had any ideas as to why this is so oddly intermittent
and works after I resolder U3??

One last note: The explosion sound that comes last in the speech test
is always there and plays perfect. It's produced by the cpu sound
circuit though. All other standard sound in the game works fine.

Any ideas? Something is intermittent for sure. Maybe a cracked trace??

 

[Lindsey]

Good guess

Once I glanced at the schematics I remembered that the coil would stay energized while the switch was closed. At that point it was pretty obvious what likely happened. Not really a guess so much as deductive reasoning. hehe

 

[shardian]

Surely someone here has messed with a sys. 9 speech board? I'm dead in the water on that front. Any ideas after reading my issues?

 

[shardian]

I have finished all the repairs except for the speech board, so I started on the shop job. Due to the extreme amount of stress cracking, I'm only going to clean it up and do a basic polish on the non-mylar area. I don't want to risk removing any playfield paint. There are a few minor wear areas that I will touch up in a quick/dirty way. I'm also touching up the cabinet in the same manner. For these kinds of touch-ups, I use oil based paint markers. They are durable, quick and easy. I'm not too worried about exact color matching.

Here is what the playfield looks like stripped.

This is by far the easiest playfield I have worked on. I went back to the labeled baggie method for stripping. It only took about 40 minutes to tear the whole thing down.

 

[shardian]

I use Bleach White to clean the playfield. There was plenty of dirt present, and everything brightened up nicely once clean. The mylar is very dull of course. I did a single pass with Novus 2 on the non-mylar areas. It looked very nice after one pass.

Next I prepped for the mylar polish. It is always a very good idea to tape off the area you will be using the treasure cove kit on. Polishing mylar is where the treasure cove kit really proves its worth. Have you ever tried to polish mylar by hand? Basically, you can't. If you did you would take hours to do a small area, and it would be sub par. I dd 2 passes of #3 polish, and a single pass of #2 and #1. I did occasionally drift on to the non mylar area just to see how it handled the high speed polish. I think you could do the non mylar area if you are careful.

 

[shardian]

And here you can see the results of the mylar polish. This takes about an hour from picking up the tape to putting the tools away. As you can see in the sheen example, it is quite glossy now.

Now I am ready to put all the parts back on, re-decal all the targets, and get this game wrapped up.

 

[Schusler]

And here you can see the results of the mylar polish. This takes about an hour from picking up the tape to putting the tools away. As you can see in the sheen example, it is quite glossy now.

Now I am ready to put all the parts back on, re-decal all the targets, and get this game wrapped up.

Very Nice Shar! What's your address; I'll ship my playfield to you!

That Comet playfield looks nice compared to mine. I have some wear spots around the pops on mine and some in the cycle jump ramp. Mine doesn't have this but I've also seen other Comets that have some wear but the Funhouse hole....I might just have to try that Treasure Cove kit! I have some pins where the mylar has that cloudy effect and no way in how I can get it clean by hand!

 

[shardian]

There was wear at all the places you mentioned except around the pop bumpers. I touched them up with paint markers. You can see the red paint touchups because the marker is lighter than the actual playfield. I also touched up the dunk the dummy spot. Thy mylar had lifted in front of the target and the paint was pulverized underneath. It looked like crap, so I cut off the mylar around that area, cleaned it up and extended the black out a little bit. I still need to apply some clear coat to that spot, but it looks way better than it did.

As for the pop bumpers, if that pop mylar has ever lifted then you are screwed. Luckily all the pop mylars are intact on this one.Lifted mylar circles will DESTROY the playfield below it. The first pin I got (Charlie's Angels) had lifted pop mylars. After tearing it down, the playfield was worn way down into the wood under the mylar circles. It took alot to build it back up with clear.

 

[Schusler]

Yeah my problem with the touchup is the location. It's where there is the crowd of people so it's very detailed....

The treasure cove product would remove that cloudy effect on mylar then?