Reels lock up -- not very stiff

[JethroP]

When the machine S+ is powered on the reels lock up (is that the correct term?), but not stiff at all.  They are like barely locked.  The reels can very easily turn by hand....all three of them.  It's as if they aren't getting full power.  The machine plays normal, and the reels stop, but I think something isn't right.  Any ideas what could cause this?

[knagl]

You'll always be able to turn the reels by hand, even with the power on. The basic test is really, "Is there a difference between how freely the reels spin by hand with the power off versus with the power on?" if you're trying to determine if the reels are getting power or not.

From the description in your post it sounds like everything's working normally with the machine? If so, remember the saying, "If it ain't broke, don't fix it."

[JethroP]

Question:
"Is there a difference between how freely the reels spin by hand with the power off versus with the power on?"

Answer:
Hardly.

I agree, if it ain't broke, don't fix it.  The reason I am asking is because something isn't right. The reels (stepper motors) vibrate ever so slightly when they are at standstill.  And when I say I can turn them by hand when game is power on, maybe I should have said you can move them with just a touch of your pinky finger.
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[/size]I have other machines, I know you can move the reels with power on.  They are stiff but you can move them.  This particular machine came to me without a lot of parts.  I replaced many missing parts, including the processor board.  I noticed this machine was noisy and the noise comes from the vibrating steppers when they are just sitting still.  I swapped processor boards and this issue with the steppers follows the processor board.  Does it work?  Yes, but I don't want to sell this machine to a friend and have it fail. 
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[/size]I don't mind replacing a faulty part on the board if someone can suggest what part(s) might be bad.
[/size]
[/size]I've replaced the stepper driver chips on another board once when a reel didn't actuate.  But this machine I'm asking about now, I believe something common to all 3 reels is defective, maybe about to fail.  Besides, the vibrating noise the machine makes is annoying.

[Trisail]

The stepper motors (reels) should not vibrate at power up.

They should be held in place at power up. This is done by applying a voltage to at least one of the coils of the stepper motor. The 'Low +VS' (Voltage Stepper Motor) voltage is applied to the stepper motor circuits when power is turned on.

This terminology is what people call the 'stiff' or 'hard' or 'held in place'. So let's call it the 'stiff' feel of the reels when power is turned on to the machine. In this state when the reel is touched/spun, it will feel a bit 'stiff' as it is rotated slightly by hand. It should feel a bit 'bumpy', is the best term I can come up with to describe what should be felt. This would be opposed to when no power is applied and the reel is spun by hand and it basically free spins. The difference should be very noticeable. DO NOT spin the reels any more than necessary to determine what this feels like. The motors are coils and they will generate voltage/current when spun by hand and will apply that voltage/current back through the wires to the driver chips. This could damage the driver chips (IC's). This test of the reel 'stiffness' should not be done more than necessary. IE - don't spin the reels with power off, just to see them spin.

So a 'vibrating noise' from the reels when the machine is turned on, is not normal.

If the problem has been isolated to a bad MPU board -  This could be caused by -
A shorted CR1 diode. This would apply AC voltage to the +VS voltage, which would look like the 'Low +VS' voltage is rapidly turning on and off.
A bad connection of the +VS voltage somewhere, common to all the reels.
Bad solder connections to the MPU edge connectors, or reel driver circuit chips.
A failure common to all the reel driver chip circuitry that would cause the driver chips to apply voltage to the coils of the reel stepper motors at some frequency, causing the appearance of vibrating reels. (Not likely but possible I will assume)

FYI - The Voltage Stepper Motor, +VS is actually 2 different voltages that are applied to the reel driver circuit to hold/drive the stepper motors.
The Low +VS is used to hold the reels, lock them in place when they are not being driven. Without this voltage the reels would drift or spin on their own. Not good for a machine that must know which symbol is on a pay line at all times.
The High +VS is switched in/on when the reels are driven - stepped/spun - to a specific symbol that will stop on the pay line. Good for a machine that must know which symbol is on a pay line at all times.
So - Low +VS is applied to hold/lock the reels in place any time the machine is on. High +VS is applied when the reels need to spin to line a symbol up on the pay line. IE: Low +VS, spin reels, High +VS turns on, reels stop, turn off High +VS and Low +VS takes over automatically.

Hope this helps.

Tony

[JethroP]

Tony:
That information was helpful to understand the board design.  Thank you.  Looking at the board it is discolored under CR1.  It is darkened indicating CR1 must have gotten hot at some time, but it doesn't appear shorted and measures good.


Using my binocular glasses I checked all the header pins, solder joints, and board traces.  I don't find anything unusual.  The board looks all original and very clean.


Is there a way to measure low +VS with he board in the machine?  If so, what should the low +VS be?
Thanks again for any support.
Jethro

[Trisail]

According to the schematics I have been able to access - the schematics I have looked at, the device designators appear to be different on the boards I am familiar using. I have been able to use the schematics and determine which devices are being represented.

With that said -
The schematics tell you to test the +VS voltage -

To test the two different voltages go into output test 40 and place the - lead of your meter on anode of D2 (it is marked BGND) and place the + lead on the metal tab (collector) of Q20 and measure the voltage it should be approximately 7.0 VDC then press the spin reel button and the reading should change to approximately 11.5 VDC +/- 1.5VDC

What I do is remove the hopper, remove the MPU tray with the board and place the + lead (mini grabber lead) on either
Q19 metal tab   or
the Cathode of CR1 ( the band/strip end )
these are the same connection electrically, I carefully feed the lead up and out the top of the tray so the lead will not get pinched. I then carefully put the tray back in the machine.
then I use any metal part of the cabinet as ground/return for the - lead (mini grabber lead) and plug the leads into my meter and power up the machine. (This method will only require one lead to be clipped on the MPU board and feed out the top so it does not get pinched)
I watch the meter as the machine powers up and this is the low +VS voltage ~ 7 VDC
You can do the 40 test and press the reel spin button and see that the voltage changes to the high +VS voltage ~ 11.5 VDC.

You will notice the device designators do not match - Q19 and Q20, again revision differences? The picture below is the MPU board I am familiar using, 570X, this one is 570 7.

I hope this helps get you some more information and maybe we can determine what the problem is, or we check something different.

Tony

[JethroP]

My measurement for low +VS is 5.7 VDC
When the reels spin, high +VS goes to 14.3 for an instant then settles at about 13 VDC.


Is 5.7 VDC too low?

[Trisail]

I would say 5.7 VDC is too low. My memory is not the best but I am pretty sure a working machine showed > 7.5 VDC upto 8.9 VDC. The 14.3 to 13 VDC sounds OK.

When I worked on board that had reel tilts - mostly reel 2 but all of them would tilt at times. I found the +VS voltage was slow to increase when power was turned on. It only got up to about 1.6VDC on that machine. I reflowed the solder on the pins for the stepper motor signals on the main connectors J1 and J2 on the MPU board (not the motherboard) and that fixed the reel tilt problems.

This is the info I put in this post about the pins to resolder/reflow.  POST - http://newlifegames.com/nlg/index.php?topic=32159.msg171237#msg171237

I know this sounds a bit out there but worth a chance as you have determined the MPU board is the bad part. You can't really hurt anything if you re-solder (reflow) the J1 and J2 connections, just don't short or solder bridge any of them. There are 4 connections for each of the 5 reel driver chips that go out the J1 and J2 connectors to the stepper motors, you have 3 reels so those are for sure which ones to do. So 12 connections needed (reel 1 has one connection going to J1, reel 4 has 2, the rest you need all go to J2, I did not put J2 on the others) -
reel 1 = J1-30B, 11A, 17A, 19B | reel 2 = 19A, 20B, 21B, 20A | reel 3 = 21A, 22B, 22A, 23B ( reel 4 = J1-10B, J1-10A, 15A, 13A | reel 5 = 23A, 24A, 27A, 25A in case for those that have 5 reels that see this post in the future)
Do all the connections if you like, or just do each reel one at a time, if this should fix your problem and you want to know which one(s) may have been the bad ones, do one reel 4 connections at a time and try the board.

Your voltage is higher - 5.7 VDC not > 7.0 VDC - and that is telling me there is definitely something wrong. 

One thing you could do before you try to fix the pins on J1 & J2 - measure the +VS with your meter but measure with meter on AC instead of DC, this will check the AC ripple and let us know what that might be. I suspect it may be high as you have a vibration issue as opposed to reel tilt. The AC reading should be low in the mV (millivolt) range. Do that and let us know what that voltage reading is. I have not checked a working machine but a normal reading would be < 10mV. If you get a reading above 50 mV, maybe even 1.0 volts AC we can try to determine what is causing that. I am going to assume you will see some kind of AC ripple voltage that would explain the stepper motor vibration, who knows maybe just the low 5.7 VDC is the cause. If not, I will see if I can think of something else to check.

I have 2 questions for you -
Any chance you have an oscilloscope or scope meter?
I would like to clarify - have you determined the MPU is the problem? Have you tried another MPU in this machine and it works OK?

Tony

[JethroP]

OK, so with the reels at standstill I measure 2.4 VAC.  Not good, right?
I can't really get a good measurement when the reels are spinning because the refresh rate on my DMM, but I believe it dropped to the mV range.
I do not have a scope....only DMM and logic probe.

Maybe irrelevant at this point, but I can clarify your additional question.  I tried another MPU in this machine and the reels are stiff and no noise/vibration.  I also tried this "bad" MPU in a known good machine and it displayed the issue with the reels and noise/vibration.  So I am confident there is an issue with the MPU, not the machine.

[jay]

The two places to look are the resistors on the corner - 5 there are 5 of them, and the reel driver chips which are usually socketed.
The S+ can handle 5 reels, although we rarely see more than 3 on our side of the pond, I understand that the 5 reels were common in Oz.
You can play swaptronics by moving the 2 likely good components into to the suspect spots.


Usually 1 of the 3 go and not all 3 so the problem might be in one of the voltage traces that is common to all 3.

[Trisail]

I see Jay replied before I could finish this.

But -
The 2.4 VAC is very bad. The big 6800 ufd capacitor has got to be bad. That is the most likely problem with the vibrating reels as that is very high AC ripple. I have not had to replace any of those caps with the machines/boards I have worked. They do go bad, so I am sure that will fix your vibration problem. The schematics say it would be C12 or C21, but I'm pretty sure it has a different designator. I would replace all 4 of those big capacitors, they are the same age. One of them could be 10000 ufd so be sure you pay attention to what you remove and where you put them back. I have a 10000 ufd 16 V, but it may need a 25 V rated cap, and I have the 6800 ufd caps I think are 25 V rating. I need to look at my boards when I get home later to be sure what it takes and what I have. You can put the 25 V ones in place of the 16 V ones no problem, always OK to go up in voltage but keep the cap value the same if possible (ufd value), physical size is the thing to be sure they fit on the board. These capacitors are snap in style aluminum electrolytic capacitors you will need to get.

PM me if you have trouble finding some to purchase, I can send you what you need if I have them, very reasonable. I bought the 6800 ufd ones a while ago when I was doing the work putting an Arduino in an S+ to control everything. 

Tony

PS: The cap would have been the most logical part to check for the vibration in the reels, but I have not heard of this problem before so I wanted to check the +VS voltage 1st before we suggested replacing the caps. Looks like a 1st time for everything.

PPS: The reel driver chips may need to be replaced if you are thinking of selling the machine. I'm pretty sure they didn't like the AC ripple at all. AC ripple is bad for chips, increased current and heat. The stepper motors are most likely OK, they are a lot more forgiving than IC's (chips)