Anybody repair Sega Star Trek boards?

Thanks again, I'll give it another try tomorrow. From what I remember, pat said mine didn't have the led on it. We did swap one of the XY boards so maybe that had something to do with it? I don't know. Do you have pics or references to where the molex connectors into the pcb cage? It could be possible I hooked them back up wrong. Like, what connectors go to the sound, XY boards?

Thanks

Well looks like a problem with the XY boards. Did you remove the XY boards? Sometimes I have had to reseat the boards a few times to get them working and that ribbon cable that connects the two boards can sometimes be a problem with bad sockets or the ribbon cables themselves can be bad. When ever I remove the XY boards I remove them as a pair leaving the ribbon cable connected and reinstall them together as a pair. It's to easy to bend the ribbon cable pins trying to install them with the boards in the cage. You could have a bad video RAM on the one XY board. Have you put the game in test mode? If you cant read the test screen the red LED on the MPU will flash out an error code if their is an error. You might get an idea on what to try by watching my video from the 29 minuet mark where I was having an issue with my XY boards.
 
This is for the dedicated and cockpit but the board connections are the same, just has the 3 molex plugs on the cage instead of the 44 pin edge connector.
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Even if you don't unplug the XY Timing-Control ribbon cable it can still go bad and cause problems with the picture.

It's possible when moving the boards in and out the ribbon cable messed up. But that would mean both sets had faulty cables...or there's something else wrong. I've ordered new 2114a rams just in case . If I can't figure this out, Douglas would you be able to take a look at them?


Thanks guys!
 
...So my question now is, DID the messed up Star Trek sound board mess with the XY boards on both the Star Trek boards and now eliminator? I would suspect no but I suppose it's possible. What do you guys think?

Yes, sadly, it is possible.

It's possible when moving the boards in and out the ribbon cable messed up. But that would mean both sets had faulty cables...or there's something else wrong. I've ordered new 2114a rams just in case . If I can't figure this out, Douglas would you be able to take a look at them?

If you have a ROM burner, install the SEGA diagnostic ROM onto a CPU board and then try just the CPU, XY Timing and XY Control boards.

As VC said, Mark is the man. I'm just squirrel tryin' to get a nut.
 
Yes, sadly, it is possible.



If you have a ROM burner, install the SEGA diagnostic ROM onto a CPU board and then try just the CPU, XY Timing and XY Control boards.

As VC said, Mark is the man. I'm just squirrel tryin' to get a nut.


Ok. Thanks for the advice. I'll give it a try today
 
I've repaired a few of these sets now. They are their own special beasts to work on.

I'm not taking any additional repair work at this time, and you've already had a couple of good recommendations, so if you do isolate which boards are bad, you have some good options of go to guys for the repair work.

It has been a while since I worked on the last board set, but I did repair one XY set that had similar display issues to yours. I can't recall if the cable was involved in that problem, but it could have been.

It sounds like some of your boards may have survived which is good.

The ribbon cable that interconnects the 2 XY boards and the associated sockets for them can be a source of trouble. be careful when swapping XY boards as the pins are easy to break off, and flexing of the cable can lead to conductor breakage (usually near the entrance to the connector ends).

Good luck with your repair.
 
Thank you...just out of curiosity, the board you have that was similar to my issue...do you remember what was the cause of it? Thanks
I've repaired a few of these sets now. They are their own special beasts to work on.

I'm not taking any additional repair work at this time, and you've already had a couple of good recommendations, so if you do isolate which boards are bad, you have some good options of go to guys for the repair work.

It has been a while since I worked on the last board set, but I did repair one XY set that had similar display issues to yours. I can't recall if the cable was involved in that problem, but it could have been.

It sounds like some of your boards may have survived which is good.

The ribbon cable that interconnects the 2 XY boards and the associated sockets for them can be a source of trouble. be careful when swapping XY boards as the pins are easy to break off, and flexing of the cable can lead to conductor breakage (usually near the entrance to the connector ends).

Good luck with your repair.
 
Alright, so here's what I found out. The ribbon cables on both sets do the same thing on either sets. So I don't believe that's the issue.

The results of swapping the XY timing boards or both the eliminator and Star Trek boards resulted in these findings:

We will call the top board of eliminator XY the timing board or #1. The bottom board of the eliminator XY board with the 2114a ram Ram board or #2.

And the Star Trek XY timing board #3, and finally the Star Trek 2114 ram board of the XY boards #4.

So combining #1 and #2 gives the same results as seen in the photos, as does #1 and #4, but, #3 and #4 OR #3 and #2 give a different display as in a bunch of dots and not lines or objects at a 45 degree angle. The Eliminator CPU and rom boards I believe are good, as are the Star treks. So either the XY boards of the eliminator are good, and the #4 board of Star Trek is good, and there's just a display problem. Or they are all bad. Oh, and both cpu's Do have the led.

Any thoughts? Also, new 2114 ram will be here Thursday..though I get the feeling it won't fix the issue

Thanks
 
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Do you have any way to test the 2114s? Some EPROM burners have the facility to test RAM. Or if you have another game that uses 2114s and there is one that is socketed, you could swap your G80 chips in one by one. Tedious but an option if you don't want to wait until Thursday.
 
Or if you have another game that uses 2114s and there is one that is socketed, you could swap your G80 chips in one by one. Tedious but an option if you don't want to wait until Thursday.


This.^^^

This works really well, if it's any Atari board. I actually have an Asteroids PCB that is nearly fully socketed, that I use to test 2114's, and all other TTL and analog chips (which are fairly common across many/most of the Atari boards I work on.)

It's also nice, as it tests the chips in a real environment, at the speed that they are normally used, so you get a pretty reliable test.
 
Do you have any way to test the 2114s? Some EPROM burners have the facility to test RAM. Or if you have another game that uses 2114s and there is one that is socketed, you could swap your G80 chips in one by one. Tedious but an option if you don't want to wait until Thursday.

I've got a ms pac that does. I'll give it a try! Thanks
 
From the picture, it does look very much like just a loose/bad XY Pair ribbon cable/connection, which often causes that 45 degree look. Potentially dots as well. But there's the potential it could be more considering it sounds like you let out some magic smoke.
 
From the picture, it does look very much like just a loose/bad XY Pair ribbon cable/connection, which often causes that 45 degree look. Potentially dots as well. But there's the potential it could be more considering it sounds like you let out some magic smoke.

Magic smoke lol. I shouldn't laugh but that's funny. The speech and sound board took the big 120 acv hit....as they smelled the worse and a few chips had tiny visible holes. Anybody sell those ribbon cables?
 
Sorry to hear about your troubles, it's never a good feeling when a problem suddenly becomes worse. Vector games are their own beasts when it comes to troubleshooting but perhaps I can shed some light on where to go next. I've fixed many Star Trek boards and I'm in the midst of a repair now so the schematics are pretty fresh in my mind.

The power supply outputs four voltages: -5 V, +5 V, -12 V, +12 V. The +5 V is used on every board, as this is a common voltage for almost every IC. The other three voltages are used to supply power for the op-amps on the speech and audio boards, the op-amps and DACs on the XY timing board and a few other miscellaneous ICs. From your description of the board swaps into Eliminator it sounds like the ROM and CPU swaps were a success and did no damage to anything in the Eliminator. These boards only use +5 V. The sound and speech boards, which had visible signs of damaged ICs, use all four voltages and seemed to cause an issue with the XY timing or control boards in Eliminator. Based on this, perhaps an IC on the sound or speech board (or both) failed in such a way that it created a short across the op-amps, DACs or other IC on the Eliminator XY timing board and took out those previously normally operating ICs. You do have a largely 'normal' looking picture so my gut says the DACs are okay. When they go bad, you get almost nothing close to a normal looking image. I've found many more bad op-amps than DACs in my repairs and op-amps are plentiful and inexpensive. The slanted text also looks like a timing/counter issue, which is controlled by some 74xx TTL but that can be saved for later troubleshooting once the boards are back to a stable state.

If I were you, here is how I would approach the problem to try to work your way back to a normally operating board set:

1) Replace any visibly damaged ICs or other passive components such as small capacitors or resistors. Look carefully on all boards since the voltage rails are common to all of them. Anything that looks like it took heat should be replaced.

2) With all boards out of the cage individually measure resistance to ground across all four voltage rails on all boards. This can be done by placing the black lead of your multimeter on the ground plane (the plane all around the edge of the board) and the red lead at the -5 V, +5 V, -12 V, +12 V at the edge connector pads. You should get roughly 100 ohms or more for +5 V and something in the kohms or Momhs range for the other three voltages. Anything close to 0 ohms or a very low resistance means there is a component on the board that is shorted to ground, perhaps from the power supply shock. Pull up the schematics and begin looking for ICs that use the shorted voltage. Remove one at a time and measure resistance after each removal. When you find the IC that results in a return to higher resistance that is likely a suspect IC.

3) Since you have new 2114 RAM on order, it doesn't hurt to replace them all just to prevent back and forth removal of the boards should any of them fail the RAM self-test. 2114 RAM is generally sensitive to transient voltage spikes and I've found dead 2114 RAM several times in the board sets I've troubleshot. You can always keep the originals as spares if some of them test good.

4) Replace all six boards in the card cage. Measure the resistance to ground similar to step 2 above, but of the entire card cage assembly. This can be done by measuring at the DC wiring harness edge connector on the side of the cage. Again, anything with 0 ohms or very close to ground should be considered suspect.

5) Double check all four DC voltages coming out of your power supply. Reversing the AC and DC could have also blown capacitors or other components inside the power supply. Rebuilding them is easy enough but it does take some time. Perhaps use the Eliminator power supply to test both board stacks until you can get back to the Star Trek.

6) Reassemble everything in the cabinet with the exception of the video signal going to the monitor. Any time you do repairs especially on the XY boards you risk sending some large voltages to the deflection board that could stress the big transistors on the heat sink should there still be an undetected or newly created fault in the X and Y signals coming from the timing board.

7) Power the game on, listen and look for issues such as smoked capacitors or other signs of power issues. If the game appears stable, give it a credit, see if it starts and plays blind (the sounds are good indicators of this). If the game won't boot press the red self-test button and see if the red LED produces any error codes for the RAM or halt signals. If the game appears to boot, measure the X and Y voltages at the video signal harness. Normal readings on AC volts using a digital multimeter should range from 0 VAC to 2-3 VAC and constantly fluctuating. Test for 30-60 seconds to get a good feel for range. Anything above this range and/or a static voltage that does not change indicates further issues with the XY timing or control boards. An oscilloscope is also a safe way to do this test but can be a pain to lug around. The multimeter method is usually sufficient to know you aren't going to overload the monitor.

8) If the video signals are nominal and the game appears to boot (no error LEDs) then hook up the monitor and see what you get. Run self-test again and cycle through all the screens. At this point, you should be really close to a functioning game. Any abnormalities in video or audio are probably only an IC or two away from fully working. If you still have the slanted text issue on Eliminator (or Star Trek) begin digging into the TTL that supports the timing of vector draws. It looks like an x-axis only issue so that can narrow your focus down to 50% of the timing board with only six or so TTL that control the x-axis.

I hope this helps!
 
Thanks for all of the info! I spent some time going over the number 2) portion of your advice...here's what I found. On the XY timing boards, the 5v line read around 1.57k ohms. I didn't know where exactly the other voltages were, but none of them read bad I don't think. The sound board though, read only 12 ohm on the 5v line...I am pretty sure something or a lot of things are bad with this one for sure...any advice on where to start? I'll try to measure the ohms of the whole cage sans the Star Trek soundboard which I believe may be faulty. Also the 5v line is tied to ground(I'm getting a beep and full continuity between the 5v and ground ) :(
Interesting side note, both 2114 ram chips on the sound board survived, despite possibly having a short on the board
And the 2114 rams chips on the XY boards survived as well when tested in my ma pac. 1 2114 ram chip on the Star Trek XY board was bad, replaced with a good one and still dots on the screen. Checking for continuity on the ribbon cable contact points shows continuity. Would it be worth replacing the sockets with dual swipe ones or should I leave it alone?

Thanks!



Sorry to hear about your troubles, it's never a good feeling when a problem suddenly becomes worse. Vector games are their own beasts when it comes to troubleshooting but perhaps I can shed some light on where to go next. I've fixed many Star Trek boards and I'm in the midst of a repair now so the schematics are pretty fresh in my mind.

The power supply outputs four voltages: -5 V, +5 V, -12 V, +12 V. The +5 V is used on every board, as this is a common voltage for almost every IC. The other three voltages are used to supply power for the op-amps on the speech and audio boards, the op-amps and DACs on the XY timing board and a few other miscellaneous ICs. From your description of the board swaps into Eliminator it sounds like the ROM and CPU swaps were a success and did no damage to anything in the Eliminator. These boards only use +5 V. The sound and speech boards, which had visible signs of damaged ICs, use all four voltages and seemed to cause an issue with the XY timing or control boards in Eliminator. Based on this, perhaps an IC on the sound or speech board (or both) failed in such a way that it created a short across the op-amps, DACs or other IC on the Eliminator XY timing board and took out those previously normally operating ICs. You do have a largely 'normal' looking picture so my gut says the DACs are okay. When they go bad, you get almost nothing close to a normal looking image. I've found many more bad op-amps than DACs in my repairs and op-amps are plentiful and inexpensive. The slanted text also looks like a timing/counter issue, which is controlled by some 74xx TTL but that can be saved for later troubleshooting once the boards are back to a stable state.

If I were you, here is how I would approach the problem to try to work your way back to a normally operating board set:

1) Replace any visibly damaged ICs or other passive components such as small capacitors or resistors. Look carefully on all boards since the voltage rails are common to all of them. Anything that looks like it took heat should be replaced.

2) With all boards out of the cage individually measure resistance to ground across all four voltage rails on all boards. This can be done by placing the black lead of your multimeter on the ground plane (the plane all around the edge of the board) and the red lead at the -5 V, +5 V, -12 V, +12 V at the edge connector pads. You should get roughly 100 ohms or more for +5 V and something in the kohms or Momhs range for the other three voltages. Anything close to 0 ohms or a very low resistance means there is a component on the board that is shorted to ground, perhaps from the power supply shock. Pull up the schematics and begin looking for ICs that use the shorted voltage. Remove one at a time and measure resistance after each removal. When you find the IC that results in a return to higher resistance that is likely a suspect IC.

3) Since you have new 2114 RAM on order, it doesn't hurt to replace them all just to prevent back and forth removal of the boards should any of them fail the RAM self-test. 2114 RAM is generally sensitive to transient voltage spikes and I've found dead 2114 RAM several times in the board sets I've troubleshot. You can always keep the originals as spares if some of them test good.

4) Replace all six boards in the card cage. Measure the resistance to ground similar to step 2 above, but of the entire card cage assembly. This can be done by measuring at the DC wiring harness edge connector on the side of the cage. Again, anything with 0 ohms or very close to ground should be considered suspect.

5) Double check all four DC voltages coming out of your power supply. Reversing the AC and DC could have also blown capacitors or other components inside the power supply. Rebuilding them is easy enough but it does take some time. Perhaps use the Eliminator power supply to test both board stacks until you can get back to the Star Trek.

6) Reassemble everything in the cabinet with the exception of the video signal going to the monitor. Any time you do repairs especially on the XY boards you risk sending some large voltages to the deflection board that could stress the big transistors on the heat sink should there still be an undetected or newly created fault in the X and Y signals coming from the timing board.

7) Power the game on, listen and look for issues such as smoked capacitors or other signs of power issues. If the game appears stable, give it a credit, see if it starts and plays blind (the sounds are good indicators of this). If the game won't boot press the red self-test button and see if the red LED produces any error codes for the RAM or halt signals. If the game appears to boot, measure the X and Y voltages at the video signal harness. Normal readings on AC volts using a digital multimeter should range from 0 VAC to 2-3 VAC and constantly fluctuating. Test for 30-60 seconds to get a good feel for range. Anything above this range and/or a static voltage that does not change indicates further issues with the XY timing or control boards. An oscilloscope is also a safe way to do this test but can be a pain to lug around. The multimeter method is usually sufficient to know you aren't going to overload the monitor.

8) If the video signals are nominal and the game appears to boot (no error LEDs) then hook up the monitor and see what you get. Run self-test again and cycle through all the screens. At this point, you should be really close to a functioning game. Any abnormalities in video or audio are probably only an IC or two away from fully working. If you still have the slanted text issue on Eliminator (or Star Trek) begin digging into the TTL that supports the timing of vector draws. It looks like an x-axis only issue so that can narrow your focus down to 50% of the timing board with only six or so TTL that control the x-axis.

I hope this helps!
 
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You're welcome! If you pull up the larger 149 page Star Trek manual online you can find all the schematics and nice diagrams of all the edge connector pin outs. Sega did a fantastic job on documentation for the XY games (Electrohome on the other hand didn't do so well with the G08 monitor, hah). To summarize, if you look at the edge connector of any of the cards you will see the number 1 at one edge all the way to number 43 on the other edge. Flip it over and the naming convention changes to letters from A to y. The voltage rails are shared across both sides, unlike the data lines, so you can measure from either side of the card to ground as follows:

+5 V: 22, 23, Z, a
-5 V: 24, b
+12 V: 25, c
-12 V: 26, d

In general, the higher the resistance the better and the actual, absolute value in the kohms to Mohms range doesn't really mean anything significant since the chips probably have variance in their internal resistances and will vary card to card. You are looking for dead shorts or near dead shorts as you indicated was the case with the sound card. I would put that one aside for now as it is not critical to a successful boot up or clean video image. Unfortunately, this card may be the most tedious to troubleshoot since it's a mix of many digital and analog parts. If nothing looks visually burned, it may be a bit of trial and error. I'd save that for last.

If the ribbon cable tests good for continuity it's probably a safe bet to assume it is fine especially if the cable doesn't look creased and the plastic harness terminals are nice and secure (there are small plastic clips on either side of the terminals). If the connectors come out of the current sockets without much force, the original ones may be weak. It never hurts to change the sockets to nice dual wipes. Be careful though if you do change them and try to remove the ribbon cable later on. The pins are very easily bent and finding a new one can be a pain if one breaks off.

Keep this in mind though as a general troubleshooting tip. It's very tempting to want to shot gun lots of things at once. Back when you were doing the card swaps with Eliminator did you remove the two XY cards as a pair and leave the ribbon cable intact? If you did and you didn't flex the ribbon cable in any significant way odds are it is still making a good connection. There can be TTL failure modes too that result in funny graphical issues similar to what others have experienced with a bad ribbon cable in the past. In other words, don't get too fixated on just one thing and also don't get discouraged if you've done everything to prove or disprove a bad ribbon cable or connection. The TTL on both XY boards do occasionally fail for no good reason other than age. It could have been just pure coincidence or something like the smallest bit of static-to-ground when swapping the cards that could have taken a few TTL with it depending on how you were holding it. I always touch the little metal interlock switch box inside the cabinet before I do anything with the cards just to discharge myself.

Keeping the sound card out of the cage hook everything back up and do the resistance to ground checks at the edge connector coming out of the side of the cage. If none of the voltage rails dip below about 100 ohms, especially the +5 V rail, it can be safe to assume you've replaced any parts that have been shorted to ground. There can still be parts that have failed in a different manner (not shorted to ground) that are not functioning on the XY boards.

It is important to remember the CPU can't 'see' into the vector generator logic. This means the game can successfully boot up and play just fine, pass all the RAM self-test routines but still have buggy graphics due to a bad 74xx logic gate or two on the timing board in the area close to the DACs. If you've exhausted all the repair tips to this point it will be time to dig into the XY timing board with a logic probe or other diagnostic tools.
 
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