720 Joystick

Scott1

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Hello everyone. I am new to this forum and new to owning a video game (720 purchased 3 weeks ago).


Unfortunately I am unable to play it as my joystick doesn't work properly. I am just wondering if anyone might be able to help me out. I have purchased and installed a new computer chip board for the joystick, and I have also checked my DC volts (+5) to make sure it is set correctly, mine is now running at 5.1 VDC. I also bought the metal optic disks, but did not install them as I think the old ones are pretty good. A few tiny wobbles in them but nothing more than about 1/16". Is there anything else that you know of that I can try to fix to get this thing running? I am dying to play it! It looks great as I have restored it while I was waiting for the joystick parts to come, but when they came I found out that the chip was not the problem.

Just a little more info for you as it may be important. The joystick worked when I first got the machine. I played a few games (wish I would have played more now) but the joystick was in very poor shape (but worked), so I took it apart just to lube it, and see what parts (if any) I needed to order. When I put it back together it didn't work properly again. When playing my guy does turn around, just not smoothly at all. Also when trying to direct him which way to go, he often goes into a "power slide". Does this sound familiar? Is there anything that can be done.

Thanks to anyone that can help me out with this!
 
It's probably a bad LETA chip on the game boardset. There have been a few threads about this--try searching for "720 LETA" on the forums.
 
Yeah, I had a bad LETA chip in mine. Unfortunately, they're pretty tough to come by for some reason. Someone needs to start making some repros.
 
Is there anything else that you know of that I can try to fix to get this thing running?

Take a voltmeter and measure the signal coming from optical encoder of the main disk. As you turn the main spinner disk the voltage in two wires should asynchronously move back and forth from 0v to 5v - as voltage in one wire goes up towards 5v, the other one should be going down to zero, and vice versa. Or more precisely said they should produce quadrature signal, like this:

300px-Quadrature_Diagram.svg.png



* Be careful of other lights that might interfere with operation of optical encoders.


When I put it back together it didn't work properly again. When playing my guy does turn around, just not smoothly at all.

My crystal ball says you bent one of those optical encoders a bit. Even a slight change of distance or angle between light emitter and sensor can produce exactly the kind of problem you describe. Either that or you have a light inside your cabinet interfering with optical sensors, or perhaps some pudding clogging the slots of the encoder disk.

* See if optical encoders stand vertically, check for bad connections.


Also when trying to direct him which way to go, he often goes into a "power slide". Does this sound familiar?

What is "power slide", how do you normally do it?
 
Thanks for the info on the "LETA" chip. I will look into that, and if I find some I will let you all know. Does anyone know where this "LETA" chip is in the machine? I looked for it briefly, but no luck.

Take a voltmeter and measure the signal coming from optical encoder of the main disk.

Thanks! I will try this first, as the 720 bill is getting kinda high.

My crystal ball says you bent one of those optical encoders a bit.

Negative, but good suggestion. I bought all new parts and installed them all last night. New optic cpu, and encoder disks, and still... nothing. :(

What is "power slide", how do you normally do it?

Not sure what you might call it, but thats what we called it back when I used to skate.

If you turn the joystick (while your moving forward) 90 degrees real fast your guy will do a "power slide" and collect points for doing one. But this happens to me even if I just move the stick a little bit.

Thanks again everyone! I really appreciate it. Hopefully its one of those 2 problems and I can get this thing running soon!
 
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Negative, but good suggestion. I bought all new parts and installed them all last night. New optic cpu, and encoder disks, and still... nothing. :(

720_Optic_Discs_Small.jpg
720_Optic_Discs2_Small.jpg


You replaced these three and you still have exactly the same problem? That would suggest your harness is to blame, maybe connectors make a poor contacts with Optic PCB or game board itself. This is what I would do, in this order:


* Spin encoder disc, see if always stays between emitter and sensor

* Disconnect centring disc and see if that makes any difference

* Measure 'quadrature signal' at several points, voltage on:
A.) sensor legs
B.) opti-PCB connector pins
C.) connector at the end of the harness
D.) game PCB pins once everything is connected


B, C and D should measure the same. Actually even A should measure the same, or better to say - I do not know what is the purpose of LETA Opti-PCB chip. I think it's there just to filter this signal from optical sensor, i.e. stabilize voltage and shape the signal from "round" to more defined and regular "quadrature signal", and if that is true all should work even without LETA Opti-PCB chip, which, if malfunctioning, could be making more problems than solving. [EDIT: I thought that chip on Opti-PCB is "LETA", but LETA is actually on the game board itself, still though, both of these chips seem a bit unnecessary.]

In any case you will first need to find out which wires carry this quadrature signal. See those connectors on Opti-PCB, they have four pins: one is input 5v, one is ground and the other two are your A and B quadrature signal wires. The important thing to measure, at all measuring points, is input 5v wire should have stable voltage, while A and B output wires should have fully swinging voltage all the way from 0 to 5v and back, as the encoder wheel turns, and that's also how you can identify those connector pins.



Not sure what you might call it, but thats what we called it back when I used to skate.

If you turn the joystick (while your moving forward) 90 degrees real fast your guy will do a "power slide" and collect points for doing one. But this happens to me even if I just move the stick a little bit.

Does character still stay "synced" and points the same direction as controller handle? Can you describe if and how the problem varies when you turn the stick very slowly, with medium speed, and very fast?
 
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Again... Thanks to everyone who has replied!
Sorry for the delayed reply (out of town, couldn't do the tests).
Turtle, Thanks for the help and detailed explanation, I sure hope you're right!

You replaced these three and you still have exactly the same problem?

That is correct.

The important thing to measure, at all measuring points, is input 5v wire should have stable voltage, while A and B output wires should have fully swinging voltage all the way from 0 to 5v and back, as the encoder wheel turns, and that's also how you can identify those connector pins.

Ok... this is what I found.

Input - 5.0V
Output (A&B) - When I rotate the stick fast it usually remains constant at 2.2V. When I rotate slow is reads between 1.8V, and 3.8V, and when i rotate extremely slow it reads between 1.1V and 4.4V. (all of these voltages go right back to the main board). Is this an acceptable voltage? I know you said it should go between 0 and 5. Any new thoughts?


Side note : I took a picture of my board... Can someone point out where the "LETA" chip is (or is supposed to be please) Thanks!
(This is a pretty HiRes pic, click on it and you should be able to zoom in quite far if need be) Forget it... I found it now. :)



One last thing. I don't know if this info will help but... When doing the "self test", joystick rotation test, it alway takes two revolutions to fill in all the squares. On the first time around it usually misses about 4 or 5 squares, and every time it is different squares.
 
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I had a similar issue for a few weeks up until earlier tonight! I recently rebuilt my controller and after being put back together my skater would skate in random directions or not change directions at all...I then changed out my old centering disc w/ a new one that arrived more warped/bent than the old one was but it now works perfect...go figure.
 
Ok... this is what I found.

Does character orientation points the same direction as controller handle all the time?

Disconnect second encoder disk off the Opt-PCB and see if that makes any difference?


* to calibrate controller and match its position to character orientation without second encoder present just point the stick to 3 o'clock before you power up the game


Input - 5.0V
Output (A&B) - When I rotate the stick fast it usually remains constant at 2.2V. When I rotate slow is reads between 1.8V, and 3.8V, and when i rotate extremely slow it reads between 1.1V and 4.4V. (all of these voltages go right back to the main board). Is this an acceptable voltage? I know you said it should go between 0 and 5. Any new thoughts?

That measurement looks fine, it's the latency of your voltmeter that prevents it from giving you a full reading, but if you spin it really slowly you should be able to see the whole range. An old analog meter will give you more precise reading than many new digital ones.

In any case I think you have isolated the problem. Controller and Opti-PCB seem to send correct signal, so the problem must be somewhere down the line or on the other end, thus if your harness and connections are all good this leaves us with one thing - LETA chip, unfortunately.


Well, it was worth a try I think, but until you find replacement LETA I am afraid the only thing you can try is to bypass this chip completely and see if that helps, though I have no idea how would you do this and it does not seem anyone ever tired it. But if you can find specifications and data sheets for this LETA chip, post it here and perhaps if we can figure out what it does and then maybe we could do something to fix it.
 
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