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Taito Speed Race resto


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IMG20180908184713.thumb.jpg.5eb00adf802ef8aa61035be78d834425.jpg

 

So here they are, my two latest boondoggles. Speed Race and Space Rider, they'll side up nicely next to my mame machine once I (hopefully) get them back in operating condition. For now the best thing I can say about them is that they are complete, without any obvious evidence of electrical carnage taking place inside. In fact the pinball machine looks surprisingly good inside for something that is a decade older than I am. It looks unmolested with a mint backglass, but the same can't be said for the Speed Race cabinet. It appears as if someone has added an aux power supply circuit for the CRT, although I'd be lying if I said I knew what these things are supposed to look like inside.

 

I've decided to embark upon the restoration of the Taito first as it seems less daunting at this stage. This thing was sold to me as a 'dead screen' deal, but I'm not so sure that this is the case. When I power it up I get a dead screen, that familiar crt whine, a glowing neck and the time/score panels seem to be functioning. So nothing on the display and and no sound. One thing I did notice was when I turn off the power, a white dot appears in the middle of the CRT before fading out.

 

I do intend spending the rest of the night combing out of this forum whatever chunks of wisdom I can find, but a little kick in the right direction would be much appreciated. Does this smell like a CRT fault or an issue in the logic somewhere?

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Sweeet. Thanks dude.

 

That's just what I needed to sort out this rat's nest. The more I look, the more I find. Someone had been keeping this thing on life support, doing surgery with whatever was close by. I think I can see at least 3 'eras' of wiring here.

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Cheers mate.

 

It'll make a nice change of pace from cars and bikes.... At least these things aren't covered in 'vintage' grease. And I get to learn all about digital electronics.

 

I have kinda been putting it off. In the workshop, once things get beyond 'replace the blown cap', it's time to order a replacement. Somehow I don't think that's going to be a viable option here.

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Cheers mate.

 

It'll make a nice change of pace from cars and bikes.... At least these things aren't covered in 'vintage' grease. And I get to learn all about digital electronics.

 

I have kinda been putting it off. In the workshop, once things get beyond 'replace the blown cap', it's time to order a replacement. Somehow I don't think that's going to be a viable option here.

 

Mate, you have exactly the right attitude for this sort of stuff.

There are many instances where you really have to find a ton of previous info / failures and fix it yourself.

The Taito has plenty of support and info, the Atari, not so much.

I applaud your enthusiasm and I'm sure there will be a ton of enthusiastic supporters on the forum here where any questions can be answered.

I am not an arcade guy but I think your Taito problem may be a board issue rather than a display issue.

Neck board lights and video decay dot indicates to me that it thinks it's doing what it should, however I am not an arcade guy.

Ask me a pinball question, (not Atari ):D

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I am not an arcade guy but I think your Taito problem may be a board issue rather than a display issue.

Neck board lights and video decay dot indicates to me that it thinks it's doing what it should, however I am not an arcade guy.

Ask me a pinball question, (not Atari ):D

 

I'm inclined to agree. At this stage I'm hoping that it's an issue somewhere between the board and the CRT. Who knows, it's a mess in there, I might get lucky.

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More than likely a logic board issue, you can double check by connecting the video output from the PCB to any TV (CRT or LCD will work) via the AV input. I've never tried it but I'm guessing that you could conversely connect a console with AV output to the monitor input and see if it displays an image.

Have you confirmed the board has +5v at the chips?

Do you own a logic probe? It's essential if you plan to try to fix this board yourself but without a schematic or chip numbers it's not an easy task.

I'm guessing that the PCB will have the writing on the chips sanded off, Taito did this in the early years to stop the game being copied. This makes it very difficult to know what's expected from the chip inputs and outputs.

 

Below is the databook for Midway Wheels which is very close to Speed Race, there isn't a schematic available for Speed Race that I've been able to locate.

Though not exactly the same, they share many similarities.

 

https://drive.google.com/open?id=0B0kAwpS2NEYzVTJiRXR0djJVUVE

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That's a good place to start for sure. I'll see what I can work out in the morning. I haven't done any diagnostics aside from looking at it and plugging it in as yet. I'm still holding out hope that it could be something simple like a power supply issue, it looks like that whole side of things has been messed with.

 

I did notice the sanded chips when I pulled the main board, thought it was odd. A logic probe is on my shopping list for tomorrow and I'm bracing myself for the dive into the intricacies of digital stuff. I figure this has to be a good place to start.

 

Thanks for the data, I'll add it to my files. A schematic for this thing would be awesome, google found me one for the Atari in 0.000012 seconds....

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Good luck with both projects,

 

It sounds more like a board fault as previously mentioned i tested the last B&W monitor I worked on using the AV plug from a vhs player perfectly clear black and white porn I mean boobs I mean Care Bears oh who am I kidding it was porn

 

 

Sent from my iPhone using Tapatalk

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Jaycar sell a Logic Probe kit for $15 or you can order one from Ebay for about $30+

 

https://www.jaycar.com.au/logic-probe-kit/p/KD6100

 

This is the type I use.

 

https://www.jpmsupply.com/Logic-Probe-and-Pulser-Combination-Elenco-LP-900-p/80311.htm

 

Thanks for the tip. I went down to Jaycar, picked up a kit for the logic probe and put it together. Also dragged my old oscilloscope and bench power supply, so I'm all set up.

 

I hooked up my VCR to the screen (Austin Powers if you were wondering), and after extensive fiddling with the contrast, V-hold, brightness and focus, I was rewarded with this.

 

IMG20180909171427.thumb.jpg.96104095b24f71f95f9499e0a25ca3c3.jpg

 

Too dim, not enough contrast and seriously lacking v-hold. I can clearly see a number of swollen caps on the CRT board, so with my total lack of knowledge of CRT circuitry I'm going to assume those things are related. Any chance somebody has already complied a list of capacitors for this screen?

 

More interestingly though, when I hook the feed from the main board I get this:

IMG20180909175031.thumb.jpg.1c5767b00f06f9792a70aea07cec5b38.jpg

 

Still same erratic, dim picture... But I guess at least some of those little black chips are still functional.

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After some further knob twisting and bypassing a few decades worth of shitty wiring I now have this:

 

IMG20180909184545.thumb.jpg.c314fafc5a9181f5582cb0c347267091.jpg

 

A half-way functional machine. Maybe 'half-way' is being generous. After powering up and tripping the coin circuit the game runs with a stable picture, I have sound and the throttle is working. The score counter works as you can see by my hi-score of 242. However the timer is not functioning, there is no 'player' sprite and the left line of the road is faint. But hey, it's progress.

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So this is interesting. Broken lead on the bypass cap that sits between pin 14 (vcc I guess?) on every chip in bank 7 and earth. Because of it's position I thought that I may have broken it while removing the board, but I replaced it into the machine and got same results. Somebody has also (poorly) replaced a 555 timer in bank 10, but no continuity issues there.

 

 

IMG20180909230337.thumb.jpg.83c9264208dafed3b636d6b1093aff70.jpg

Edited by SeaJay
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Ok, so the cap has been replaced, and no joy. Well, not much. The screen is looking better, the left and right sides look much more 'even' now. I could see tires on the cars for the first time but after I started poking around with my logic probe I somehow managed to change the car sprites to something weird.

It's hard to get a clear pic of it but -

IMG20180910161146.thumb.jpg.ade56555303cd4b67cdedf3f83178006.jpg

 

So after probing around, the only thing I came across that stood out to me was - Two chips with no output and and also no activity at the playing time adjustment pot. I've either got high, low or toggling everywhere else. I marked the area where my problems seem to be in the pic below.

 

IMG20180910161209.thumb.jpg.9b297bfe975237be1eda8412aa88bcce.jpg

 

 

After some more poking around the car sprites went back to normal, then switched back once again. Any knowledgeable folks around that can chime in?

Edited by SeaJay
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As there is 100+ ic's on the board a symptom you decribe is not likely to appear somewhere online.. or even happen to anyone else, so unfortunately there will be a very slim chance of.. "That happened to me". Consider the combination of chips and input outputs we rarely if not ever see the same symptom twice.

 

Keep probing away. It's logic probe diagnosis 101.

 

Find chips that aren't doing what you'd expect them to be doing and you're in with a chance. Counters and flip flops seam to go first. So 74161 7474. You can usually find them looking at the clock inputs and Q outputs. Not easy flying blind.

 

I'm actually pleasantly surprised you got a semi-working pcb. Completely dead is a lot more work so it's a great start.

 

See how you go. If I have time I could look at it for you. I've repared a number of these. Good luck. :)

Edited by taito
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Thanks for the reply. It's my first time time playing around with a logic probe so forgive me if I seem a bit slow. I probed every ic, all expect two are doing something when the game is running. I have found one cap leading to one of them that is reading low on one side, with no reading on the other. Every other cap on the board I can check reads low on both. So I'm going to swap that out and see what happens. I'll let you know when I've thrown my hands up, if it gets to that and you can bail me out I'll make sure it's worth your time.

 

IMG20180910172437.thumb.jpg.385ef648360bdbd3d94fd22caf5e990a.jpg

 

Any opinions on this? Looks like a repair, but the trace is broken. I'm not sure if it was done purposely or not. The pin with the wire on it switches high and low at about 1hz and the pin on the other side of that trace stays high.

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Not seen that before, (the trace). Almost for sure its an attempt at a repair or a little mod. Logic would dictate that the pin should have the same waveform as the point at the end of the wire. But I can't say for sure. Sometimes it's difficult trying to work out the purpose of other people's work.
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It seems like that wire is a repair and that trace was supposed to be broken. I bridged it and lost randomization for one of the cars on the screen, it stayed on the far right of screen. No luck with the Cap change. I'm starting to suspect that 8 pin IC. I'm guessing that in the case that it is toast, there will be no way to identify it?
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Nah. Fuji boards have their ic chip markings. There's a few of us who can help you out. I went looking for mine but found an exta midway space invaders pcb so I've been tinkering with that. Ha

I'm pretty sure they are very similar.

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great work so far.. well done man.

 

there will be no way to identify it?

 

yes there is.. mr @crackerjack ( i think it was) once sent me pics of a fuji pcb and i also collected others back when i was kidding myself i would one day have time to work on my own games. i still have them and will pm to you ( files is a 32meg zip dont try and download it on your phone.

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It seems like that wire is a repair and that trace was supposed to be broken. I bridged it and lost randomization for one of the cars on the screen, it stayed on the far right of screen. No luck with the Cap change. I'm starting to suspect that 8 pin IC. I'm guessing that in the case that it is toast, there will be no way to identify it?

 

I'd hazard a guess and say that the IC in question is a 7474.

Pic below is one of the Fuji PCB images @wiredoug sent me as well as yours for comparison.

The traces match up with slight variations between Taito and Fuji.

 

i9ud7vt.jpg

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That's beautiful, Thanks heaps. I'm still a bit out of my depth with all this but that's going to fill in a lot of gaps...

 

And my sprites are back to normal... The game actually looks reasonable now, aside from from lacking a player car.

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Another handy tool to have is an IC tester/identifier, the 74xx (not LS/HC) are getting harder to find and there's no point replacing something that is working.

You can pull a suspect chip, chuck it in the tester and it will check and identify it for you.

I have a similar one to the link below but it's USB powered.

 

https://www.ebay.com.au/itm/Multi-Function-IC-LED-Optocoupler-LM399-DIP-CHIP-TESTER-Model-Number-Detector/151765528456?hash=item2355ee2f88:g:EN8AAOSwOudZv8wM

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