Can't clear Main Battery Low message

[knutt185]

Hello,
I have searched the forum and still cant figure out the problem I'm having with my IGT Game King.  It has the 044 board.  I got the main battery low message so I pulled the board and replaced the battery.  I tested the battery that was originally in the board and it was at 3 volts.  The new battery tested at 3.1 volts. I also cleaned the battery holder.  Restarted the machine and still had the message.  I tried the clearing the message with the attendant switch on the side and also the reset button on the front of the board holder.  Nothing.  When i hit the reset switch or turn the attendant switch it takes me to the attendant menu and shows the main battery low message in pending tilts.  I tried a ram clear with the Key28 chip and when that didn't work I used the Key28 chip again and cleared everything and set the machine up again.  I still get the same Main Battery Low message.

If anyone has any suggestions for me I would be extremely happy.

Thanks
Ken

[Tilt]

 

Clearing, resetting, etc isn't going to help you with a battery low error.  It'll only clear when the machine sees battery voltage in the proper range. 

Check the battery voltage with the battery installed.  Put the + on the top of the battery holder and the - to the metal tray.  Note that voltage.  Then move the + lead to U65 pin 8 (it's about an inch from the battery) and see what you read there.  Then get back with the results.

[knutt185]

Thanks for the reply, Tilt.

Voltage at the battery is 3.1.  I do not get any voltage reading on pin 8 on U65.  I do get 3.1 volts on pins 1 and 5 though.

[Tilt]

I think that you may have got the IC pin numbering off a little.  I attached a picture of how it's numbered just FYI, but your battery connection is good to have battery voltage at that point and that's what I needed to know. 

Since you have good battery connections and voltage I think you have a problem with a voltage divider network that's used to set the reference voltages the machine looks at to determine when the battery is low.  I've fixed a couple of 3902 MPUs that had the same problem and they had resistors in a divider network that drifted way out of tolerance and caused the machine to think the battery was low when it wasn't, which is what yours is doing.  I've never had a problem like it my 044s, but it's a similar circuit to the 3902s.

I don't know if you have the tools to replace SMD resistors or not, but here's the schematic for that network.  Check the resistor values in the red box and make sure they're what they should be.  If you find one or more out of tolerance replace it and that should solve the problem.  If you don't have the tools or don't want to mess with it I'd contact member Lookes and see if he can take a look at it for you.  It should be a pretty easy fix.

[Tilt]

I forgot to mention that some of those resistors may be on backside of the MPU board.  If so, you'll need to remove the MPU board from the tray to get to them.  1/2 the battle is just locating these little components on the board!

[knutt185]

Thanks again for the help Tito.  I did get the pin number off a bit.  I found the resistors in the schematic you sent.  Of course they were on the back side of the circuit board.  Dang they are tiny.  Nothing like the resistors I worked with when I was younger.  I did measure the values and attached a sheet with the results.  I tested with the battery in and battery removed from the board.  The one resistor, R392, I couldn't get a reading on when the battery was in since the meter was jumping all over the place but I was able to get a reading with the battery removed.  This is supposed to be a refurbished board.  I had the same issue a couple months ago and took it to my slot guy.  He said the other board was bad and needed to be sent in to be repaired.  I got this board back and within a few days ended up with the same low battery message.  It makes me wonder if some of the resistors are bad if there is something else going on with the machine that is causing issues with this board.

[Tilt]

Yeah, they're pretty tiny aren't they?  R392 and R393 are reading too low, but you may need to remove them in order to get an accurate measurement.  Other than the resistors U26 is the only semiconductor in the chain that could possibly be bad.  My experience has been resistors though. 

It's hard to say what may have been done to the board while it was out of your hands or even if you got the same board back.  Marking it or recording the serial number is really the only way to know if it was the same or different. 

If you have the equipment/skills to remove and check those give it a shot and see what they read.  If not, well I guess you could try your slot guy again or contact lookes and see if he'll take a look at it for you.  I doubt there's anything else outside the MPU board that would cause this problem.  Personally I'd check with lookes, he has a good reputation for doing good work.