Before chopping the PIA's off, check some basic signals. Your CPU board isn't booting. The soundboard does but is a solitary board.

Is there a clock signal to the 6802/6808 CPU? Is the /reset signal active -> pin 40 at the 680x? Are the game roms okay? Is there 5V at pin 28 of the RAM? Change the 680x CPU, especially if it is an AMI branded one!

Are all of these okay, use a testrom. Leon coded one in the past which is easy to use. I coded one which provides more diagnostics but might be a bit more compicated to use (PM me if you would like to have it). I wouldn't just shotgun the PIA's and replace them by questionable Chinese ones.

A testrom will certainly provide you insight about what your CPU board is doing or not doing. The Reset signal is just a DC signal and easy to measure with a multimeter. Reset is active if pin 40 is low, 0 volts. The board will not boot in this case. You will need a Logic probe or oscilloscope to check the clock signals.

The PIA LED will just be stuck if your board isn't booting. You can check if the diagnostics are working: remove the SRAM -> turn the game on -> the PIA LED will flash one time. If this diagnostic signal is working it tells you the board is at minimum starting its diagnostic routines; also telling you the reset signal and clock signals are probably okay.

AMI chips are unfortunately a common failure point. It is worth to try another 6802/6808.

Also check the IC sockets for the CPU, ROMs and SRAM for corrosion due to a leaking battery. At IPDB.ORG you will find the gamerom binaries.

There *seems* to be a communication problem between MPU and Soundboard. The sound PIA at the MPU board can be defective -dead outputs or a dead Interrupt capability. There can be a problem with the band cable too. The Input buffer/latch (LS374) also is suspect at the soundboard. I would start with testing your MPU board with a testrom and trying another bandcable.

Good luck!

A PIA can have some defective outputs and the rest of its internals can still function okay. In this case it is possible the PIA is not detected as being defective. Try to test the MPU board with the testrom I send to you earlier. It has a PIA initialization test and a test which cycles the outputs at an about 1Hz cycle. Easy to measure with a (fast) multimeter. You can also connect an LED with series resistor to test each output (pins 2-17, 19, 39).

Indeed interesting results. There is a time difference between us - sometimes a catch a thread at pinside sometimes not…..

In a nutshell....

- your board boots and plays, but without sound and displays are also not behaving as they should (can be a displaypanel also)

- The PIA init test is failing at the first display PIA ($2800 base address) - the others seem to respond.

- The Lamp control PIA is dead at the testrom output test, but with gameroms it is doing its job as it should.

Is the Switch matrix test in the testrom performing okay? (activate an input results in a pulsing output ??)

Hard to Judge at the distance unable to see and perform some measurements. I would be very interested about the selection signals to each PIA at pin 23. An oscilloscope is a useful instrument for this, I hope a logic probe will catch this signal also. Why the selectionsignals? There is a possibilty one of the PIA's is permanently selected, eating the data meant for another PIA. This is not an easy fault at your board....

Congrats! I have a Time Machine myself, it is a very addicting game with a very nice lighshow and good sound. It will never leave my collection.

Now the 2 Nummerical displays. The message "bad switches" is followed up by mentioning the faulty ones at the 2 lower displays or a simple "none", but as the displays are not working at all you won't see this .

The display glasses themselves can be dead. You can check the B I/O port (pins 10-17) for activity with a logic probe from the display PIA at 11B. They control the segments from the nummerical displays. The digit strobing (PIA 11B I/O port A and 74LS154) works as that controls the strobing for both the alpha- and nummerical displays. The alpha's are up and running so there won't be a problem there.

About the testrom….you inserted that one in socket 5C? It should be mentioned the testrom is a benchtest thing and not meant to use in game. You can do it but you should disconnect the connectors for the coils to avoid damage. The low frequency pulsing of the outputs can cause damage.

As you seemed to have intermittent problems in the beginning -after reinserting the gameroms the MPU started suddenly- i think it is a good idea to replace the IC sockets from the gameroms, SRAM and 6802/8 CPU.

The pitch is 2.54mm

If the nummerical displays are working fine, then no. PIA 11B controls the digit strobing for both the nummerical and alphanummerical displays. It controls the segments for the nummerical displays too. PIA 9B controls the segments for the alphanummerical displays.

You are using the testrom in-game. Probably you had the coindoor closed this time; then the memory protect feature kicks in. The testrom will no longer pass the memory test as it is unable to write a certain part.