Screen Burn Arcade - Exidy 440 Repair Logs

Exidy 440 Repair Logs
By: John Havel (Cmndr Brain) © 2016

Exidy 440 boards were used in several gun games starting with Crossbow in 1983 to Who Dunnit in 1988. These consist of a two board stack. The MPU board and the Audio board. Because the two boards are stacked on top of each other, this makes it difficult to trouble shoot unless you have a bench setup that can address this issue. Years ago, I made a portable test rig. Using the power supply and connections from that test rig with a Jamma to Exidy 440 adapter, that I made, I'm trying to bench test some broken boards.
This information is only from my own research and testing. This is not gospel. This information to here to help me organize and document my notes and repairs and to help others repair their boards as well. If you are reading this, use this information at your own risk. If there are mistakes that you are aware of please contact me at: srgntbrain@gmail.com

(Exidy 440 Test Rig Setup)

(Jamma to Exidy 440 Adapter)

Exidy 440 Pinouts and Jamma Conversion

Minimal Setup:
I've found that the minimal setup to test the MPU boards are:

Cpu 68B09E must be installed at 1H
4 Program Roms at 1A, 3A, 4A and 6A must be installed.
2 6116 Ram chips must be installed at 8A and 10A
All screen rams must be installed : B14 - E21
All custom proms must be installed : 3K - 8K, 2H, 9H and 12H

I've found that the minimal setup to test the Audio boards are:

Cpu 6809 must be installed at C3
DMA Controller 6844 must be installed at E3
Program rom must be installed at 1H
6116 ram must be installed at 1G
Sound roms must be installed at K1 and K2

You can power and run an MPU board by itself.
From Tom (aramis): "I've confirmed that you can get some of the self-test info on the screen even with the audio board completely disconnected. It gives an audio board error, but you can definitely focus on bringing a dead cpu board back to some sense of life without the audio board complicating things."

General:
440 Board stacks have 2 processors. Be very careful! Even though they have the same 6809 designation they are very different. On the audio board there is the 6809, where as the mpu board has a 6809E. The 6809 has an internal two-phase clock generator and only requires a crystal while the 6809"E" designation requires an external clock generator circuit. Do NOT mix these up.
Any letter between 68 and 09, e.g. 68B09, refers to the maximum frequency of the processor.

A = 1 MHz
B = 1.5 MHz
C = 2 MHz

The schematics show the Exidy 440 boardset to be equiped with "B" 1.5 MHz processors. So, B or C are acceptable.

As different games were produced, Exidy implemented a crude security system into their game boards. By changing a chip or two, they changed some of the logic on the board set and wrote the code of the the new games to compensate. On the MPU board, the chip located at 18J, originally had a 74LS244. The 74LS244 is a non-inverting octal buffer/line driver with 3-state outputs. Some games would substitute a 74LS240 inverting chip. On the audio board, the chip located at 1A, originally had a 74LS367. The 74LS367 is a non-inverting hex buffer with 3-state outputs. Some games would substitue a 74LS368 inverting chip.

Some boards had jumper wires manually soldered on from the factory. Some of these were to fix design flaws, while others were used to change the logic of the board depending on the game.

Exidy 440 Monitor Sync

As far as I can tell, dedicated Exidy 440 games were wired to the monitor using the separate Horizontal and Vertical Sync lines. The video connector has a Composite Sync pin (Pin 7). These sync signals are positive sync lines. A jumper pad at E3 has two filled in holes on the MPU board, near the video connector, that has a trace connecting them and setting the board to positive sync. If negative sync in required by a monitor, the trace can be cut. A 2 pin male strip can be soldered in and a removeable jumper can be used for positive/negative sync selection.

Exidy 440 MPU Boards

Boardset Alpha (MPU Rev. A)
18J = 74LS244
NO Factory Jumpers

Symptoms and Repairs:

Will boot with hardware error.
- Orginally had Chiller roms installed. Since there were no factory jumpers and the ic. @ 18J was a 74LS244 this could not be a Chiller board. Installed Crossbow roms.
Boots to Blue/Yellow bars.
- Oops. Crossbow eprom 3A pin 12 bent when installed.
4 Position dip switch hard to switch due to dips crushed from use.
- Replaced dip switch @ J19.

To Do List: