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Dark Tower Game Links > Dark Tower Online > Dark Tower Slideshow > Keypad Repair > Dark Tower Circuit Boards >  
Updated 05-22-2017 pm
Dark Tower Board Game Circuit Boards

This will be an ongoing page with details about the different versions of the  circuit boards used in the Dark Tower Board Game.

Recently a friend sent a Tower that has an alignment problem when showing the Warrior, Food and Beast column.   The column was slightly to the left and not centered.  I've read on another site that a quick fix is to angle the clear diode down a bit and test until it centers better.  As I was making the adjustments, I noticed this tower was possessed by a sort of free electron demon.   It was very weird power on behavior.  On power on, the display would occasionally show an 8 only in the left display and do nothing else or a left digit eight with a rotating tower.  This spinning tower may stop on it's own and eventually display the 2 dashes or just keep going.  The lights would all be on and very dim also.  Power off and back on randomly would clear the problem.   I was challenged to find, what I thought was, a faulty part!

So, I removed the main board and speaker, motor and keypad and connected the parts on the test bench.   The battery holder with cable was attached and the switch used to turn the board off and on.  The power on problem was very random.  For example, it will power on with a normal selftest, left digit zero then dashes, 5 times with no issues then go crazy for 10 times in a row.  I replaced the battery cable wires, checked the crimps, removed, cleaned and polished the battery terminals.  After all of that work,  the tower continued to display the random power on problem.  The board also consumed a heavy amount of current.  A new set of "D" batteries were quickly depleted.  The amp meter displayed a 1.3A draw when the lights and motor are spinning.  I also could not connect my regulated power supply no matter how I changed the settings or current amount.  It would switch from voltage control back to current control and then cut back.  I could not get enough power for the board to power on at all.  The supply seemed to see a short and would turn down the current.

So, I used my perfect working tower as a donor to aid in quickly finding the problem part.  The idea was to swap parts until it's fixed.  First, I swapped the big items, the 3 chips,  no fix!  Still random weird power on issues.  Swapped transistors, no fix.  I swapped everything on the boards!  Still not fixed.  

The 2 boards use the wide DIP 28 pin processor chip N1LL to be compatible.  I noticed before that the circuit boards were different versions.  The bad board was A01 Rev B.  My tower board was a B03 RevB.   I assumed the same circuits also.  I'm thinking something else is up here!

So, I started looking around at the different sites with pictures of their boards and the parts used.  So far, I've seen 6 different versions of the main circuit boards and 3 chip versions.  My guess is that the answer lies in the idea that they made numerous changes to fix issues during production of the Dark Tower Game.  The early versions may have had known weird power on problems.  Read the Dark Tower instruction booklet in chapter 3.  There is a very detailed description of weird behavior and what to do.  If there is a problem or erratic behavior, turn it off and wait 10 seconds. Then turn it back on.  That tells me that there were issues from the start of production and there were ongoing fixes made.

***** UPDATE 04-29-2017 5:04pm *****
The weird power on issue with A01 RevB board is fixed.  I noticed a wire change on a tower with a A03 RevA board that I just received for repair.  I tried the change on the A01 Rev B.  Boom! Fixed the problem.

Here are the details:  This A01 RevB board seems to be an early version that included a circuit change already.  The change in the circuit includes using a 9112 transistor, a .47 uF electrolytic cap, a 1k and 1.5k resistor at the white connector for battery power/motor/speaker.  I verified on the A03 RevA board that this circuit change is incorporated into this version.  So that circuit change has stayed in the design.  I've compared traces and connections with this mod and it matches the external change on A01 Rev B.  Maybe they created the first PCB labeled A01 RevA.  Maybe they didn't release this board.  If anyone has any details on this board, I can add it to the group.

So, on the A03 RevA, I noticed that there is a white wire connecting U1 Pin 4 of the processor to U2 pin 9 of the 75494.   That was another nice clue to say, yes they made changes because of some problem.  On the A01 RevB board U2 pin9 was connected to Batt-.  I made the change in the PCB by adding the wire and removing the wire jumper.  It worked.  Fortunately, this circuit change was about the issue I was having with my A01 RevB.  The circuit change involves: removing the wire jumper from U2 pin 9 solder pad to the other connected solder pad that connects Batt -,  then add the wire from U1 Pin 4 to U2 Pin 9 solder pad near pin 9.  The board was then tested with several power on and off cycles including random off times in between power on.  Then completely testing with quick games at level 4.  I then tried connecting my regulated power supply and it worked fine.  Do more drained batteries.
Wow! No more weird power on problems! The Free Electron Demon is gone!  

********** UPDATE 05-01-2017 **********
Another tower came in the mail today.  It was another A01 RevB board.  Exact same issues.  Removed the jumper, added the wire.  Tower complete.

The next question is.  Why pin 4?  Pin 4 and 5 were originally left unused on the early Rev boards.   Pin 5 is is unused as seen on an E01 RevA.  It's seems to have started with pin 4 then to pin 5 then back to pin 4 that is used to route U1 Pin 4 or 5 to U2 Pin 9.   I decided to test this change on the A01 RevB,  I moved the white wire on U1 pin 4 to pin 5.  I fully tested with the same good working results.   BTW the U1 pins 4,5 are just above - voltage.  At about +.3V.   I don't have an answer to that besides it works also...   I have not seen an internal diagram of this chip.  Just the obvious, follow the traces and create a schematic based on it's working and that's what the pin are connected to.  The only way to answer is to made a complete schematic to start understanding the circuit better.

Do the later versions boards after A03 RevA that use the U1 28 pin SDIP package size labeled N2LL have the same internal configuration as the original wide DIP 28pin N1LL chips?  Moving the wire from U1 pin 4 to pin 5, it still works but why was Pin 5 chosen over pin 4 in the earlier Rev boards with this similar change?

So, the next feat is to document these boards with pics and schematics to show differences.  So far we have the boards front and back to compare.  They all function the same. Same chip program.  As long as make the change to the A01 Rev B boards.

A01 Rev B, A03 Rev A, B03 Rev B, D01 Rev C, D02 Rev C, E01 Rev A

There are 3 chip types with the same program code. MP7332-N1LL,  MP7332-N2LL  and maybe the last batch of chips labeled DCRS MP7332-N2LL.  The N1LL is the first released as a wide 28 pin DIP package and the N2LL and DCRS N2LL are a smaller SDIP package still at 28 pins.  The same internal pinout for the N1LL and N2LL.   The DCRS N2LL is using another internal pin layout.  Still the same program code but just shifted the pins internally.

Question: 05-01-2017 ==> There is something confusing about the E01 boards and the processor chip PCB pinout.  Were these chips wired incorrectly?   Were the internal pins changed?  I'm just referencing the obvious unused pin4 which appears to be on the wrong side.  It looks like the pinout got flipped around in the chip...  I'll have some pics up to show what I mean.

Answered: 05-02-2017==> An excellent source of TMS1000 info I have found in Sean Riddle.  The puzzle is answered.  The chips were manufactured using a internal pin layout of the TMS1100 chip.  Normally the chip was wired internally according to the TMS1400 pinout.  Still not sure why this was necessary as this changed caused a new PCB layout to be created.  Sounds like a CF with the chip manufacturer.  E01 PCB boards are reconfigured for this chip internal pinout change.

 ***************** TO DO'S ****************
Add more pictures of the different versions of boards with Fritz schematics and maybe some theories to the changes.
There aren't any functionality differences.  The program is exactly the same in all versions.  Changes were made in the circuits for reliability.

A01 Rev B without U1 and Bulbs
Needs Jumper Removed from U2-9 to -Batt.  Add wire from U1-4 to U2-9 Solder Pad near Pin 9
This is Sean's Board used to create the very interesting snapshot of the processor die.

A01 Rev B
Motor Mod Circuit Added from Factory.  Needs U1-4 to U2-9 Wire Added

A01 Rev B
with TMS1400NLL Labeled and I added the U1-5 U2-9 wire.

05-22-2017 am
A01 Rev B
The earliest release board known without the Motor Mod or Power Mod Circuits
On first inspection, the original U2-9 jumper to -Batt was present and the motor mod was not!  The Power On Circuit Mod was added from U1-4 to U2-9.  The tower tested fine so now it's possible to move onto finding out what this motor mod circuit solved.  With the board, motor, speaker removed from the housing,  placed on the test bench, it was obvious that the motor continued to spin a bit longer after self test has completed.  Next was too run L4 game and watch the motor.  Same thing,  the motor spun a bit longer when inventory was checked.

The board, motor, speaker were installed back in the tower to test with the carousel.  The problem that the motor mod solved was very obvious!   The tower continues to rotate a bit after completing self test.  Placing the carousel a bit to the left instead of centered.  Then after starting a L4 test game,  it became even more obvious.  The tower continues to rotate more after each column is displayed during inventory.  In an L4 game, you have everything so the tower carousel spins displaying your inventory and drifts left more each time a new column is displayed.  By the time the last item is displayed -the sword- the carousel has drifted past the sword.  The alignment fix of adjusting the LED's didn't help as this problem is exponential with each column being displayed.

The motor mod circuit was installed using a 2N2907 transistor.  This PNP transistor is very close to the Hfe of the original 9112 transistor.  Now the motor turns on and off much faster with the extra current.  Again, reassembled and another problem cropped up though.  The carousel is misaligned to the right.  What??  So I compared the carousels with another.  I've never noticed this! They are different!  The carousels are labeled  1 and 2 in the clear plastic.  That might be a mold number though.  The black rings used for the column alignment are different.  There are no markings at all on this back ring.  The spaces are the same size but one is shifted compared to the other.  This may be a huge problem as this carousel version may make the motor circuit mod incompatible!  Still working on this...  An idea would be to shift the LEDS further in or out from the board.   The motor mod circuit proves it value as to stop the motor faster for better alignment.

05-22-2017 pm. Watching the slot timing as the carousel turns and when the light appears through each slot to when the motor shuts off, it was determined that the leds need to be on the other side of the board.  Measuring the difference of where the black slot ring was mounted in each carousel was about 1/4".  This should get the alignment close then tweak the LEDS to fine tune alignment. The LEDS were remounted on the other side of the board and it works great.  It took a bit of time bending the leds to get a perfect alignment but it works great.  The self test worked fine then an L4 game checking inventory, all the columns lined up correctly. 

So, this A01-B board has the power mod and the motor mod circuits to perform as well as the later released tower boards.  90 hrs later...  but a fun problem!  Can you imagine what the game designers went though. 
 ... a long time ago... in a far away -- board room, the MB marketing managers had a big meeting with the game designers about Dark Tower returns and angry merchants!  "These tower are not working correctly and we're getting too many returns...  fix it! waaaa!"

A03 Rev A
The Motor Mod Circuit embedded in PCB.  Power Mod U2-9 to U1-4 wire already added from the factory.

B03 Rev B
The Power Mod wire has been embedded into the PCB connecting U1-4 to U2-9

D01 Rev C without U1 and Bulbs. Sean's Riddle cadaver board.
This is a D01 board version with the SDIP sized U1 Processor Chip.
I can assume that is the reason for the D version PCB. This version also wires
 the Power Mod wire to U1-5 to U2-9.  U2 is flipped around.

D01 Rev C

D02 Rev C - Overseas Atlantis Game
I'm not sure was changed in D02. The PCB traces and parts/locations appear the same.

E01 Rev A
This is the latest released version known.  The U1 chip internal pinout and PCB changed.  U1 and U2 have been turned around.  The power mod circuit is changed again to U1-4 to U2-9.  Error or intentional?  The PCB traces are thicker with extra solder pads in different locations.