Star Trek SOS repair - not my idea of a good time

Here's hoping you can answer a couple of questions for me that might also prove useful to others in the future.

I'm trying to use a logic probe on the cpu board. Where would I be able to clip the red and black leads on the cpu board to power the thing? The test points for +5?

I'm trying to probe the "coin drop" signal; if I ignored the logic probe and tried to use my DMM, would that likely pick up the coin drop pulse or would it probably be too fast for the DMM to register?

At the moment I'm trying to probe pin 9 of the 74LS00 in U6 but I'd want to hit pin 10 as well for the switch NO line and pins 12 and 13 for the NC line.

Edit: I found some +5 and ground connections on the Z80 but I can't possibly clip the alligator clips on the logic probe to chip legs, they're way too big. What to do?

Since I've got an ATX supply powering my board set I get +5 and GND from one of the molex connectors on the supply.

If you're testing in a cabinet the safest place to get them would be directly from the power supply. But, according to the cabinets wiring diagram pin 2 of P1 should be brown which is +5. You should be able to use any of the large grounding braids as your GND reference assuming your connection from logic GND to earth GND is good.

If you're on a workbench get your +5 and GND from the power inputs on the board set or from the power supply. There are a few GND posts on the CPU board.

the end result of the coin circuit that you are testing is at pin 6 of U9, Id start there and work outwards. A DMM will register a change but it wont be fast enough to see if your getting a good "state change" unless the meter has the ability to record (some flukes do) then you could look back at the results.

You could also probe at the coin switch to make sure your connections to the board set are good as well as the resistor pack at RP3. Which ever coin input that IS NOT connected to ground should go high. If they dont you have a broken wire or that resistor pack is bad. I'd go with broken wire. :)
 
I was out in the garage tonight looking for my stash of G80 parts. I thought I had another set of boards somewhere but I could not find them so maybe not. I did find enough G08 parts to put 2 monitors together but I only have one frame,tube and yoke. I do have 2 back planes, one without the cage and one in the cage. I'll test my dedicated Star Trek tomorrow and if it's working I'll pull the XY boards and send with the back plane.

Thanks Sam. You've already helped tons but a tested and working set of XY boards would be great. Then I could get down to business on the rest of these boards.

Outside of the spikes in the data lines on the RAM I'm not seeing anything that would inject these random instructions into the pipeline. And after shot gunning that entire XY control board of mine I find it hard to believe that its got any more problems.
 
Since I've got an ATX supply powering my board set I get +5 and GND from one of the molex connectors on the supply.

If you're testing in a cabinet the safest place to get them would be directly from the power supply. But, according to the cabinets wiring diagram pin 2 of P1 should be brown which is +5. You should be able to use any of the large grounding braids as your GND reference assuming your connection from logic GND to earth GND is good.

If you're on a workbench get your +5 and GND from the power inputs on the board set or from the power supply. There are a few GND posts on the CPU board.

the end result of the coin circuit that you are testing is at pin 6 of U9, Id start there and work outwards. A DMM will register a change but it wont be fast enough to see if your getting a good "state change" unless the meter has the ability to record (some flukes do) then you could look back at the results.

You could also probe at the coin switch to make sure your connections to the board set are good as well as the resistor pack at RP3. Which ever coin input that IS NOT connected to ground should go high. If they dont you have a broken wire or that resistor pack is bad. I'd go with broken wire. :)

Oh, thanks! The logic probe instructions said to get the +5 and ground on the board being tested; I didn't realize you could get it anywhere like from the power supply or power wiring. I thought there could be a difference between the power supply ground and the ground on the board.

That makes thing much easier!

I did just discover that the metal test point pins on the board itself are tied to ground.

The coin drop problem is definitely on the CPU board; coin drops work perfectly with my other cpu board. When I put this one in then they stop working.

Thanks for the tips!
 
If there was a potential between the grounds that would be a problem for the probe but that cabinet should be fine.

Coin pulse should also be very easy to follow.
 
Man it would be crazy to see some of those games surface now. Imagine buying a space fury or tac/scan, getting it home, looking inside and seeing a wg6400 in there. That would blow my mind ha.
 
When I was testing a cpu board... where I didn't need all the connectors plugged into the top...
I attached the aligator clips of my logic probe to two pins on the header....

As I recall, if looking at the top of the cpu board, you have all the pins in multiple headers.... I believe I used the 2nd from the right of the two rightmost header pin groups, with + being the one of those two that is on the right, and the - being the one on the left.

I just used a DVM in diode test on the +5V feed to a chip, and found the pin, and the same for ground.... And I found a +5 and a GND right on those header pins. As I was testing in game, this was perfect as the wires were at the top and not crowding out my limited work space in the cage :)
 
Man it would be crazy to see some of those games surface now. Imagine buying a space fury or tac/scan, getting it home, looking inside and seeing a wg6400 in there. That would blow my mind ha.

One I was very fond of was a dedicated Star Trek U/R that was in great shape (this is going WAY back). I'd love to know where that game is and if the 6400 still works.
 
Got my XY timing board to put out a signal! I had a shorted LS191 @U19 that was holding several of the CO data lines down to GND.

And of course the output is a friggin disaster area. Unstable vectors are everywhere. :(

Can never be easy can it.
 
all 6 XY boards I have now display a picture but all of them throw random vectors. I can see noise all over the XY boards that coincides with the random vectors on the screen. Problem is that I cant figure out WHERE the noise if coming from.

Swapping out CPU's and ROM boards makes no change. Power supply voltages are good with no AC ripple.

Hmm....
 
One I was very fond of was a dedicated Star Trek U/R that was in great shape (this is going WAY back). I'd love to know where that game is and if the 6400 still works.

So the 6400 was a drop in replacement for the G08?
 
So the 6400 was a drop in replacement for the G08?

not exactly. Its power requirements were different (the same as 6100's if I recall right). Its drive section was pretty damn solid though.
 
When I was testing a cpu board... where I didn't need all the connectors plugged into the top...
I attached the aligator clips of my logic probe to two pins on the header....

As I recall, if looking at the top of the cpu board, you have all the pins in multiple headers.... I believe I used the 2nd from the right of the two rightmost header pin groups, with + being the one of those two that is on the right, and the - being the one on the left.

I just used a DVM in diode test on the +5V feed to a chip, and found the pin, and the same for ground.... And I found a +5 and a GND right on those header pins. As I was testing in game, this was perfect as the wires were at the top and not crowding out my limited work space in the cage :)

That's a great idea, thanks. I'll give it a shot.
 
Well, the monitor works! But the random vectors I was seeing on the scope are in fact present on the G08. :(

This is very interesting.

If you understand the vector state machine as it's described in the manual, the state machine is correctly picking up the vector formats and rendering them in some cases.

In your pictures in post #6, words and other images are rendered properly. Seems like the ships are having some issues. What's interesting is that in Star Trek, the ships aren't really 3D rendered as they'd have you believe, but simply static images that are displayed and scaled for the appearance of real-time 3D rendering.

Initially I thought of EPROM corruption, but you said you swapped EPROM boards.
The data bus must be good, as I assume the game is playable otherwise.
Then I thought, well, the vector RAM that the state machine runs over may be getting corrupted. But I'm sure you've checked the RAM multiple times. Maybe the RAM addressing is bad.

Maybe now is a good time to try the diagnostics ROM?
 
This is very interesting.

If you understand the vector state machine as it's described in the manual, the state machine is correctly picking up the vector formats and rendering them in some cases.

In your pictures in post #6, words and other images are rendered properly. Seems like the ships are having some issues. What's interesting is that in Star Trek, the ships aren't really 3D rendered as they'd have you believe, but simply static images that are displayed and scaled for the appearance of real-time 3D rendering.

Initially I thought of EPROM corruption, but you said you swapped EPROM boards.
The data bus must be good, as I assume the game is playable otherwise.
Then I thought, well, the vector RAM that the state machine runs over may be getting corrupted. But I'm sure you've checked the RAM multiple times. Maybe the RAM addressing is bad.

Maybe now is a good time to try the diagnostics ROM?

I have checked the RAM multiple times. The Diagnostic ROM shows bad RAM on the missing sound board(s) but thats because they are not there. :)

I'm very perplexed as to whats going on here. Clearly the VSM is working but some where along the data stream, outside noise it being introduced.

I've tried other ROM boards and CPU boards with these boards along with a different power supply. The only things that are common at this point is the back plane, the VL ATX-->G80 adapter, the harness from the VL board to the back plane and the ribbon cables connecting the XY boards (I have three and they all do the same thing). All voltages are clean with no ripple.

I remember fixing some old boards that had issues with LS vs non LS parts. I'm going to look over the boards now to make sure that the factory parts are all LS.

I just dont get it.

Mark, if you have a pair of known good XY boards I'll take em. I want to keep the ones I have and eventually fix them but I'd like to move the project forward.
 
And just so I'm 100% on this. Board placement on the back plane doesnt matter, right?
 
theres no possible way that this has something to do with the exact type of part I'm using is it?

I mean a 74LS74PC and 74LS74AN are the same part, right?
 
And just so I'm 100% on this. Board placement on the back plane doesnt matter, right?

Ok I got some good news. I fired up my dedicated upright Star Trek and the game booted up and the XY boards are working 100%. Yeaa, the bad news I have no speech and the sound board has gone funky but that's not a problem as I plain to install a Vector Labs multi kit in this game with a full multi sound card. I brought the XY boards into the game room and put them into my multi game to test and they work in that game too. Pictures as proof they work in both games. I also have a back plane from a Tac/Scan which is the same and yes it doesn't matter where the boards are plugged in as long as the connectors reach the proper board. Now to find a box and pack them up for shipping.
 

Attachments

  • star trek 010.jpg
    star trek 010.jpg
    188.9 KB · Views: 35
  • star trek 022.jpg
    star trek 022.jpg
    185.5 KB · Views: 38
  • star trek 036.jpg
    star trek 036.jpg
    188.6 KB · Views: 37
  • star trek 038.jpg
    star trek 038.jpg
    185.9 KB · Views: 35
  • star trek 039.jpg
    star trek 039.jpg
    196.5 KB · Views: 31
theres no possible way that this has something to do with the exact type of part I'm using is it?

I mean a 74LS74PC and 74LS74AN are the same part, right?

Looking at the data sheets for both parts the only difference I see is with the fmax-Min, the 74LS74AN has an fmax-Min of 25MHz and the 74LS74PC is 35MHz. I don't know what that means.:confused:
 
Looking at the data sheets for both parts the only difference I see is with the fmax-Min, the 74LS74AN has an fmax-Min of 25MHz and the 74LS74PC is 35MHz. I don't know what that means.:confused:

operating frequency probably would be my guess.
 
Ok I got some good news. I fired up my dedicated upright Star Trek and the game booted up and the XY boards are working 100%. Yeaa, the bad news I have no speech and the sound board has gone funky but that's not a problem as I plain to install a Vector Labs multi kit in this game with a full multi sound card. I brought the XY boards into the game room and put them into my multi game to test and they work in that game too. Pictures as proof they work in both games. I also have a back plane from a Tac/Scan which is the same and yes it doesn't matter where the boards are plugged in as long as the connectors reach the proper board. Now to find a box and pack them up for shipping.

Those monitors look great!

Thanks for the assist Sam. Want me to fix those sound/speech boards for you? Include them with the XY set and back plane board.

Its the least I can do.
 
Back
Top Bottom