1982 Sega Star Trek Captains' Chair Restoration

[zittware]

Tonight I took delivery of my new Project - a 1982 Sega Star Trek video game in the Captain's Chair configuration.





This machine completes my Star Trek arcade... as its the last one I didn't have.

It's going to need quite a bit of work... the wood is going to need some repair; and the plastics have begun to have that old plastic yellowing (can you read Retr0brite?). It currently has no vector monitor; but appears to be complete. I hope there are no circuit board issues - but won't be able to test until I get a working vector monitor.

I'd like to have this ready for TPF'2011 in March 2011; but its just too short of a time frame to do this captain's chair justic.
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[Lancer]

You should clear out the dining room and make it into an arcade.
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[Mickey21]

You should clear out the garage and make it into an arcade, oh wait, that was already the case before. Nice score Zitt, I am sure you will do it justice in time, that last ones were very impressive.
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[zittware]

I really need to move the machines into a more climate controlled env - but there is currently no room.
I guess I'll have to get some insulation blown in the garage so I can heat/cool it.

I think if I got rid of the boxed behind the pins; I'd have enough room for both the voyager and the Sega Captain's chair.

Need to finish the 7/1 surround sound in the living room next weekend. Then I can start on the Sega.
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[tempus]

personal arcade, thats sweet.

[zittware]

I finally got around to testing the Sega Star Trek board set.
This machine is based upon a G-80 arcade machine which is a vector based graphics engine. Instead of the typical Raster process. This means the graphics of the machine are crisp and clean.

I had to take a different approach to debugging this machine as I couldn't just hook it up to any old monitor. It requires a vector monitor to operate; which I currently don't have.

It turns out that a good electronics work bench would have an Oscilloscope. Mine happens to have two. Many ?all? Oscopes have an X-Y mode. So I decided to hook the video output of the machine to the oscope. The Yellow "Y" goes into the "Y" for the Oscope (aka Ch2). The "X" (green) goes into Ch1 (X).

Unfortunatly; when I first powered up the board - I got nothing but a dot in the center of the display.
I did some reading and came across the G-08 FAQ which didn't really provide much troubleshooting hints save for the comment that the soundboards can be removed to minimize the boards being debugged.

More reading. Read the Manual. looked at schematics. First thing I noticed is that the Red (D3) Test LED was not easily viewed when in the cage. Second; the test switch was broken. Fixed that with a spare switch and some rework wire.

The Test button now worked. but gave inconsitent results. Some times the LED would come on and stay on. Sometimes it flicker rapidly. some times steady. Umm. More looking / investigating. I figured at this point; I needed to actually bench test the board. Check for obvious problems... IE Reset stuck low. Check the Interrupt lines. Etc of the Z80A cpu. It was then I noticed someone had cleanly clipped away Y1, R10, and R11. Not desoldered. but cut off near the board. <sigh> That'll do it ... no clock gen means mr cpu an't getting what it neads to fetch instructions from memory.

Searched high and low for a 8MHz crystal. I just didn't have one. Radio Shack - didn't even bother. Frys - hoped but they don't carry crystals at all.

On a parts board - I did find a 4MHz crystal. I remembered from my reading that the board acutally runs at 4MHz. I also remembered that the schematics indicated the Clock was divided down by 2 thru a D flipflop (7474)... and then again to 1/2 clock frequency. I looked at the schematic again and formulated a plan.
1) Re-Populate the crystal with a 4MHz crystal.
2) Verify that pin9 of U10 (7474) was operating at 4MHz.
3) Verify pin 11 of U10 was 1/2 input (4MHz / 2 ) = 2MHz.
4) put U10 into a socket.
5) Lift pin 9 on the U10 package.
6) bridge pin 9 to pin 11.

Steps 2&3 confirmed my understanding of the clock circuit. The designers generate a 8MHz clock from the crystal using the inverter and nand gates. Then use the "D" flipflop to half that clock to 4MHz which goes to the clock input of the Z80A.
Steps 4-6 uses the 4MHz crystal to generate a 4MHz clock which is fed directly into the Z80A.

I bench powered the board and verified that the Z80A was getting a 4MHz clock.

I put the board back into the cage and power it up. The board came up and I was treated to imagery on the Oscope. WOOT!





Since the Oscope doesn't have a "Z" input the electron beam of the oscope can't be turned off went necessary; so the image shows up as just a continous beam being drawn on the screen.

This made me really happy - a little troubleshooting and the boards were all right.

Next; I need to put the sound boards back in and verify functionality.
I also need to secure a vector monitor.

The G08 Electrohome monitor used in these games is a real PIA - It's known to catch fire. As such; many are toast... proably in a landfill somewhere. I have found a person selling me one untested - which means I'm going to have to figure out how to test that puppy. I'm proably going to have to recap the monitor and do some design changes to keep mine from catching fire.

The PSU in the sega is turing black from heat; I'm likely going to need to rebuild it too.

More later - stay tuned.
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[Mickey21]

Awesome troubleshooting and great deduction.
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[zittware]

Despite not being on a time table ; I can't seem to avoid working on this project.

I was able to locate a Electrohome G08 monitor in Nevada; and while I waited for it to arrive; I went ahead and cleaned the board cage; fan; and backplane.

Before:

Eweeew.

After:

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[zittware]

The monitor arrived as untested unit; and is typical it didn't work.

My goal is to verify the monitor as good before I being the recapping process.

Initially; the monitor did not power up; and I detect both F400 and F401 as blown. I immediately checked the Deflection transistors and detected two of the transistors were shorted. I replaced them with NTE388 (subs for MJ21196G according to Bills Classic Arcade http://www.biltronix.com/Star_Trek_08.html ) on a quick run to Frys Electronics.

While I had the board out of the monitor cage; I couldn't stand the years of ... yeah; let's call it soot.

We all know it unsightly; but it's also bad for heat transfer of the key componets.

When washing boards - it's not a good idea to do it with water. We all know that water+electronics = bad. even if they are try; the contaminates in normal tap water can lead to dendritic growth or worse; corrosion. Instead I used some 90% IPA to clean the boards.... with a little mechanical brush also known as a toothbrush. Alchohol evaportates quickly and leaves nearly zero residue.

The bathroom sink?

ICK!!

After:


I replaced the F4xx fuses with 4A Slow Blow as suggested by Bill and F700/600 with 2A slow blows.

The monitor powered up and was vectoring the game; however, it only appears to be rendering a "zoomed in" image. IE I can see part of the sega banner and other graphics such as the plasma shots coming from the Klingons in attract mode.

I've checked the transistors in the deflection portion of the deflection board and they seem to be good based upon the dmm diode test. I've measured most of the voltages except HV. +9.1 is a little low at 8.5V. +400 is low at around 350V but varies based upon vector images. But unsure that those would be the cause of the image issue.

I'm not 100% sure as it's difficult to determine but it looks like the horizontal MAY be ok / unzoomed... and only to vertical is zoomed.

I posted to VectorList about the problem and they pointed me to the HV unit as well as the Yamp on the game board. The latter really confused me as I tested the board with my oscope; but I went back and checked with the oscope and indeed even the oscope screen looked bad. :scratches head:

I pulled the XY boardset an started looking for damage / burnt component. It was then I saw a stray piece of solder about 0.5" long resting neatly between two ICs on one of the XY boards. EEK. I removed it and it appears the temp solder bridge wasn't enough to damage any components.

Checked with the oscope; and it looked good on screen. Powered up on the monitor... and the arcade repair gods smiled upon thee.




Other pictures of the screen in the Flickr Photo stream.

Next up; I need to order some caps to recap the monitor; I hope that replacing all the electrolytic caps in the monitor will help to raise the HV voltage to be a little more.

I also have a spare CPU board which needs some debug... to make room for the Multi-G08 kit from VectorLabs.

I'm also seriously considering desiging a replacement G08 PSU. Yes; I can just buy a 5V switcher like others have done; but I think I want to do some more design work... higher power delivery for 12VDC fans.. and other accessories.
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[zittware]

Unlike this past weekend; today was a bright sunny day here in Austin, TX. I had gotten up early (for me) so I decided to do a quick batch of Lorne's Retr0brite Recipe and see how it did on the Star Trek side plastics.

This test piece was only slightly yellowed; it must not have spent much time in the sun; but it still served as a good test subject. Here's the panel prior to retr0bright-ing:


A closeup of the yellowing:

If you look at the bottom edge; you'll see the original white color where it was protected by the edge trim.

I applied the retr0bright using a paste brush:

and went to work... leaving it to bake in the TX sun for 6-7hrs.

When I returned home; the sun was down... and the retr0bright had done it's signature foaming chemical reaction with the top of the plastic:


Out came the water hose... and off came the retrobright:


So; how'd it turn out?

If you zoom in on the picture by clicking on it; you'll notice it looks pretty darn good. Its obvious the retr0brite worked... but there is some streaking present on the peice. I'm fairly sure it's because I used a coarse pasting brush to apply the retr0bright in a non-uniform manner. My next attempt this weekend (assume the sun is available) will be to apply the solution in a more uniform manner (read: paint sprayer).

While I had the test peice out; I wanted to see if there was a way to remove the black marks on the skin.


I didn't want to use mechanical removal ( aka sandpaper ) as it would further scratch the surface of the skin. I decided to use "goof-off" as it's known to remove black marks from floors and walls. Turns out "goof-off" was just the ticket.


Whoah - sexay!

Word of advice when using goof-off on the side plastics... the goof-off will remove the plastic from the surface. This was evident after looking at my shop towel after rubbing away the black marks. If you touch the just cleanned plastic with your finger; it's definatly sticky meaning the goof off is a solvent to the plastic material.
1) As such; I recommend only applying generious amounts of the liquid to the towel itself; never directly on the plastic - else you'll end up with "runs" in the plastic.
2) Turn the towel frequently to prevent lint and dirt from embedding in the plastic surface.
3) do spot cleans only; do not attempt to clean an entire side panel.
4) avoid handling the spot-cleaned areas until the plastic has plasticized.

Given I can work out the uniform retr0bright issue this weekend; I have little doubt that I can restore the side plastics to "near factory" condition and color.

My only concern with the retr0bright at this time is related to the side panels with art attached. I need to do some testing to see how I can protect them from the solution.
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[Sheldog23]

I think you should open and arcade / strip club. : D
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[zittware]

Would you be a regular patron or choose to cut down trees instead?

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[Lancer]

Fantastic work Zitt. I am really surprised you got the monitor working again, but I guess that is why they pay you the big bucks
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[Tech-Daddy]

Applause!!!!!
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[zittware]

Last weekend I made another trial run on the Retr0Brite for the Captain's Chair skins. This time opting to try it on one of the decal-ed sides. I started by covering the decal with waxpaper and blue painters tape - to prevent he peroxide from damaging the decal. I have no idea if peroxide would bleach the colors - but I didn't want to take a chance. I also sprayed the Retr0Brite solution on with my HVLP paint gun to get a more even distribution and to prevent the streaking seen in the previous run. I recoated the previous test peice (left) and the new test peice with the retr0brite. I modified the receipe - only putting a 1/4tspn of xartham gum in solution... so the solution was thick - but not so thick as to not come out of the gun via gravity.

Here the pieces are getting a sun de-tan:

U can really see the shade difference between the previously retr0brited piece and the new test piece - a big difference.

After two coats of Retr0Brite - over a 6hr day...


In Retrospec; I'd proably use surranwrap to cover the decal - as the wax didn't really "repell" the retr0brite like I thought it would. I'd also suggest checking the peice(s) every 1.5hrs - as the retrobrite will dry out over time.

Using GoofOff again to clean the peice from it's black streaks:


The chair peice had a tear in the plastic skin; I repaired it with 5min epoxy; however, I'm not sure the epoxy will hold long term. I may have to reenforce with fiberglass.


Over the past couple of weeks; I’ve been designing a replacement G80 PSU board for my Captain's chair. It features a new Audio Amp design; 5V and 12V switching regulators, and a "power good" signal.


Details on the design along with circuit theory are published in my Blog for those interested.
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