Author Topic: Merit Pit Boss (help) (Read 3068 times)

mainepinballrepair · « **on:** April 02, 2019, 06:25:34 PM »

I have a Merit Pit Boss 1991 which boots and comes up with Error 3. I can not find much on line to help. +5 and +12 are solid, board shows no damage and I think the Key is installed in the middle of the board. I have reseated all socketed IC's. Schematics idea would be helpful.
Thanks

Badbaud · « **Reply #1 on:** April 02, 2019, 06:53:17 PM »

Scott,
Welcome to NLG !!
A top down picture of the main MPU board may help.

badbaud

Stayouttadabunker · « **Reply #2 on:** April 02, 2019, 06:53:59 PM »

I have the Merit Dakota Superstar...same era.
Both use similar MPU's. and what usually goes is the battery that holds the settings
The battery is embedded onto the top of the memory RAM chip.
You may need a new one....they don't last forever.
I'll look for some old drawings for you.

Hey! What's that little red button on the bottom right of the screen for?

Badbaud · « **Reply #3 on:** April 02, 2019, 07:07:02 PM »

I found this site for manuals http://www.meritgames.com/megatouch-manuals/

Paul · « **Reply #4 on:** April 02, 2019, 08:04:50 PM »

Heres the manual for the 1995 version

ERROR CODE 3: This indicates that the Dallas key is incorrectly installed or programmed.
If "ERROR CODE 3" appears, check to see the key is plugged in securely.

mainepinballrepair · « **Reply #5 on:** April 04, 2019, 05:37:26 PM »

Thanks for the replies. The manuals at Merit do not go back to 1991 and do not mention PitBoss at all. The real question is does anyone have or know where I can find or make the Memory Back up with battery inbedded, can you purchase one? Or is the U1 9221-12 located in the middle of the board in the picture I provided just a battery and this needs to be cludged into a 3.3v or 4.5 volt battery for memory back up. If so, the circuit board would likely have a charging circuit on it and I could just use a 4.5v AA with a blocking diode so it does not charge? But a schematic would help. thanks, Scott I have included pics.

mainepinballrepair · « **Reply #6 on:** April 04, 2019, 05:38:45 PM »

additional pic.

mainepinballrepair · « **Reply #7 on:** April 04, 2019, 05:41:29 PM »

last pic, is this just a battery?

Badbaud · « **Reply #8 on:** April 04, 2019, 06:08:24 PM »

That Dallas block is RAM memory AND has a 3.6V lithium battery embedded in it.
The battery has died.

The battery is not rechargeable and those Dallas RAM modules are not available any where, believe me I have tried.
BUT not all is lost!! I ran into the same problem on a Bally Maverick video board and designed a work around using a standard RAM chip (8464A) and a small hand built circuit board
with a CR2032 battery, a couple steering diodes and a 33 uF tantalum capacitor.
The steering diodes anodes connected to the +5 Vcc and the + of the CR2032 battery, their cathodes connected together to the + of the 33 uF and that

connects to the capacitor that goes to pin 28 (and 26) of the RAM chip.
In the picture attached, a earlier mod where I connected directly to the RAM chips pin 28 and 26, you can see the decoupling cap right above the RAM chip that I should have connected to.
Give it a try.
Badbaud

Paul · « **Reply #9 on:** April 04, 2019, 07:59:29 PM »

here is one on eBay and the data sheet

https://www.ebay.com/itm/Dallas-64K-Nonvolatile-SRAM-DS1225Y-200-28-DIP-originals-NOS/252289436691?hash=item3abd9f4c13:g:YskAAOSwPc9Ww0Jw

Badbaud · « **Reply #10 on:** April 04, 2019, 08:35:32 PM »

It won't work, the battery inside is dead.

Stayouttadabunker · « **Reply #11 on:** April 05, 2019, 06:50:49 AM »

Quote from: Badbaud on April 04, 2019, 06:08:24 PM

...designed a work around using a standard RAM chip (8464A) and a small hand built circuit board
with a CR2032 battery, a couple steering diodes and a 33 uF tantalum capacitor.
The steering diodes anodes connected to the +5 Vcc and the + of the CR2032 battery, their cathodes connected together to the + of the 33 uF and that connects to the capacitor that goes to pin 28 (and 26) of the RAM chip.
In the picture attached, a earlier mod where I connected directly to the RAM chips pin 28 and 26, you can see the decoupling cap right above the RAM chip that I should have connected to.

That's an awesome fix BB!

I actually found and bought a Dallas ram chip for mine years...wasn't easy to find even back then.

Badbaud · « **Reply #12 on:** April 05, 2019, 07:28:43 AM »

The Dallas chip was designed so the battery would not be connected until the chip first saw Vcc.
Once Vcc was seen the battery was permanently connected internally and started to drain.
The problem is the battery does not live forever even if it is disconnected internally.
Just like any other battery they didn't have a infinite shelf life and considering most Dallas chips were made in the early 80's the batteries in them are ALL dead by now.
I designed with those chips years ago and had a tube of 10 that had never been activated when I started working with Larry.
We had sold 6 over the years out of the tube but the last 4 had dead batteries and had never been activated in a circuit.

mainepinballrepair · « **Reply #13 on:** April 05, 2019, 05:44:52 PM »

Ok I think I have it, if BadBaud could take a look and verify my schematic I'll give it a go. Thanks

Badbaud · « **Reply #14 on:** April 05, 2019, 06:15:49 PM »

The two diode cathodes go to pins 28 and 26 and are connected to the + of the cap.
The - of the cap goes to logic ground not 28 and 26.

Badbaud · « **Reply #15 on:** April 05, 2019, 06:42:24 PM »

The - of the battery also goes to logic ground of course.

FireballJackpot · « **Reply #16 on:** April 05, 2019, 09:32:16 PM »

Awesome Fix, BADBAUD!

Wish I had known about that 20 years ago! We tossed many of those boards because of "Error 3"'s. We even had them in the Multi-Game counter tops with the little daughter board that added more games to the menu. Ahhh, memories.

MAINEREPAIR: Looks like your 4900 needs a cap kit (Dark to bright from side to side).

mainepinballrepair · « **Reply #17 on:** April 12, 2019, 05:33:57 PM »

I rigged up the circuit which was suggested by BadBaud with the new MB8464A and no dice. Game boots shows waiting testing then same Error 3. I pulled the board out and checked and while powered up I had ~5 volts on the memory on pin 28 and 26 and powered off I had ~2.4 volts with CR2032 and I actually tried it with a 4.5 volt AA set up as aux battery power which with diode drop provided 4.0volts. I tried pressing the reset buttons on power up but no real affect. Suggestions or do I canabolize it! Thanks, Scott The cap is there for decoupling only correct?

Badbaud · « **Reply #18 on:** April 12, 2019, 06:28:20 PM »

The 33 uF is there to smooth out the transition from the battery voltage to the 5 volt logic voltage.
No voltage bump.
Did you completely remove the NVRAM module below the RAM chip and plug the RAM chip directly into the PCB socket?
You should have read close to 3.1V under battery voltage.

mainepinballrepair · « **Reply #19 on:** April 12, 2019, 06:44:44 PM »

With the triple AA's -3 the voltage was 4.8- 0.56 = 4.2 volts which should be fine as its a 5volt part, with the CR2032 the voltage would is about 2.5 volts. I removed the DS1225Y with the DS1218 mounted to the bottom of it. Maybe an electolytic 22uf cap?

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Author Topic: Merit Pit Boss (help) (Read 3068 times)