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Taito Speed Race resto


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That's a nice gadget. I've got one on the way.

 

So a little more progress. I replaced that bung 8 pin IC, a 555 I now know that thanks to you guys. Anyway the timer is now functional, just one LED out on it. Gotta get that little car on the screen and I think we'll be good.

Edited by SeaJay
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Don't ever take out those link wires you see on old boards. They are rarely there to bypass broken traces. They are usually hacks provided by the board manufacturers after you already took possession of one of there new boards only for them to identify problems that you the owner had to do. Some where to improve reliability or a fault they identified that without it would greatly reduce the life of the board.

 

That explains why many of these links you can take out and the board seems to continue working fine.

 

You have Buckleys chance of tracking down these such factory mods paperwork but I can tell you we had drawers of them and the mods were all done accordingly.

 

Because we bought so many brand new factory boards and bootlegs we were always doing these links on video game boards.

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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.

 

So I checked the 74161n ICs, out of 10, 4 of them had a bad clock. And if I'm looking at it correctly the clk on all of them are connected...

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Here's the trick. We dont know what's bad or not. Find out what's up stream of the clock inputs see if they're doing what they should. That gismo that @Kaizen recommend will come in handy. ( I'll have to get one of them myself). Before desolderind, establish what seams the chip most likely to have the problem. As there's usually two chips involved it's not always clear which is bad while they're in place. Sometimes I clip a leg which separates input of one chip from output of another. But I'm not keen on that method and use it sparingly.
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So after giving myself a bald patch from all of the head scratching, I still haven't pinned this down. But it's gotta be this clock signal. At least I'm learneding (as Ralph Wiggum would say). I love how logical all this logic stuff is. Edited by SeaJay
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That is a good tip, I did force myself out into the daylight to take care of some gardening. Can be tough to pull yourself away when you know that you're close. I'm pretty sure it's either of the two chips in the 1st bank, closest to the oscillator.
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So I guess it's time for an update.

 

I'm pretty sure the bad clock is causing the remaining problems with the Speedrace machine. I have the chip tester on the way, but I'm not keen on pressing on with the cabinet restore or the CRT cap refresh until I have a fully functioning board.

 

Now as for the Atari, I looked it over, checked fuses and fired it up. All I got was some lights flashing on the play-field, but not attract mode, as was to be expected. Looking over the main board, I noticed corrosion on pins of the CPU and the ROMs. I though a quick fix might be a re-seating of the chips so I gave it a go. Now I have more lights flashing in a different pattern and all of the solenoids firing randomly. As in all of the solenoids fire simultaneously, seemingly at random.

 

Looking closely at the chips, the corrosion on some pins extends into the 'body' of the chips themselves, especially on the ROMs. I cleaned the pins manually and tried again with the same results. Everything seems to work, as in all of the lights (without blown globes) flash, all of the solenoids fire and the score/credit displays show random numbers at random times. So I think its a safe guess that driver circuitry, psu and so forth is working ok.

 

I figure that replacing all of those corroded chips would be a good start, so I'm eagerly awaiting the arrival of some 6800 Motorola's, some 2761 EPROM's, a EPROM writer, a UV eraser and an IC tester, with BIN files ready to go. Not really sure what else to do for now.

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I figure that replacing all of those corroded chips would be a good start, so I'm eagerly awaiting the arrival of some 6800 Motorola's, some 2761 EPROM's, a EPROM writer, a UV eraser and an IC tester, with BIN files ready to go. Not really sure what else to do for now.

 

Pray to the Atari gods.

 

Got to admit though, you know your shit. Based on your first post on the forum, I kind of assumed you'd bought a non-working Atari with no knowledge on how to fix it. You clearly have the knowledge.

 

Still, pray, pray a lot :) If you get that bastard running, there will be more than a few impressed people on the forum.

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@namastepat

Pray to the Atari gods.

"Yay tho I walk thru the silicon valley in the shadow of 70s' TTL,

I will fear no fault, for my logic probe is with me,

thy flashing lights and my soldering iron shall protect me

in the depths of credit board darkness.

May thy vengeance be upon any intermittent continuity issue."

Edited by SeaJay
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@SeaJay, I would recommend that if you plan to go through the caps on the monitor that you get hold of an ESR meter, pull the caps one at a time, mark the polarity on the PCB ( small dot on the PCB with a marker pen to indicate -ve) and test the cap first before replacing it. If it tests okay put it back in and move on to the next one.

A shotgun approach can introduce new problems and the quality of the caps from back in the day can be better than the new ones you put in. "If it ain't broke, don't try to fix it".

 

Just my 20 cents worth...

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@SeaJay, I would recommend that if you plan to go through the caps on the monitor that you get hold of an ESR meter, pull the caps one at a time, mark the polarity on the PCB ( small dot on the PCB with a marker pen to indicate -ve) and test the cap first before replacing it. If it tests okay put it back in and move on to the next one.

A shotgun approach can introduce new problems and the quality of the caps from back in the day can be better than the new ones you put in. "If it ain't broke, don't try to fix it".

 

Just my 20 cents worth...

 

Solid advice, I'll follow it. I do actually have two multi-function component testers on the way also. I found them mispriced at $1 inc post each on Ebay so I ordered two. Didn't want to press my luck too much. Apparently he sent them, we'll have to wait and see. I was planning to give away the spare one to someone on here that could use it.

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  • 3 weeks later...

Just been waiting for everything I ordered to show up. Everything has arrived except for the EPROM writer. Actually I ordered one only to realize that it does not have 25v write capability. Live and learn on that one... Anyway another should be here Monday.

 

Today I removed the two suspect chip and ran them through the IC tester and lo behold, one is stuffed. It's the second one in the 10th bank, so I guess that explains the dud clk signal. I soldered in some sockets and ordered some SN7107's, I'm fairly confident that Speedrace will be sorted once they arrive from the UK.

 

As for the Atari, I have some NOS 6800's and some 2716's, so I guess I'll have some more answers once I can write the BIN files....

 

My ESR meters showed up, surprisingly... So here it is.

 

IMG20181006150645.thumb.jpg.10c9982e7a49b636bf35032807d55dc3.jpg

 

As I said before, as a sign of gratitude to the forum for all of the help and support I've received, I'm giving away the spare to the first (Aus residents only please, it'll cost more to send it OS than it is worth) member here to put their hand up in this thread. But people be cool, let it go to someone who can use it to help them resurrect some of these old machines. Don't claim it if you are going to throw it on your already extensive pile of test gear or wanna make 10 bucks flipping it on Ebay...

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Thought you guys might be interested in seeing my mame machine. I know it ain't the prettiest in the world, but it was built out of the scrap I had lying around the shed. It's running a Pi3 through a 24 inch (I think) Panasonic 100hz flat CRT that I traded with my grandmother for a 40 inch LCD. Total investment (aside from the LCD) was around $150. Really wish I hadn't cheaped out on the buttons, I'll get around to putting something decent in there eventually.

 

2006834782_IMG201810061702011.thumb.jpg.3395c6a62e392f4317e76ee4554dc92c.jpg

 

- - - Updated - - -

 

It's a TL866ii... shoot me PM if you're interested... So are 74LS107's a straight up replacement for the SN7107? If so, that would be sweet....

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Just been waiting for everything I ordered to show up. Everything has arrived except for the EPROM writer. Actually I ordered one only to realize that it does not have 25v write capability. Live and learn on that one... Anyway another should be here Monday.

 

Today I removed the two suspect chip and ran them through the IC tester and lo behold, one is stuffed. It's the second one in the 10th bank, so I guess that explains the dud clk signal. I soldered in some sockets and ordered some SN7107's, I'm fairly confident that Speedrace will be sorted once they arrive from the UK.

 

As for the Atari, I have some NOS 6800's and some 2716's, so I guess I'll have some more answers once I can write the BIN files....

 

My ESR meters showed up, surprisingly... So here it is.

 

[ATTACH=CONFIG]136795[/ATTACH]

 

As I said before, as a sign of gratitude to the forum for all of the help and support I've received, I'm giving away the spare to the first (Aus residents only please, it'll cost more to send it OS than it is worth) member here to put their hand up in this thread. But people be cool, let it go to someone who can use it to help them resurrect some of these old machines. Don't claim it if you are going to throw it on your already extensive pile of test gear or wanna make 10 bucks flipping it on Ebay...

 

Surprisingly I don't have an esr meter. Would happily grab it at that price. :)

 

Have actually been needing one for a while too! lol.

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Thanks! It will be much loved!

 

Much appreciated.

 

Sounds like you're nudging closer finding that dud 107. Good work!

 

Update: Got the gadget today and had a test run with it. Cool little device! Thanks SeaJay!

 

I love it!!!!!!!!! :) :) :)

Edited by taito
thanks
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So are 74LS107's a straight up replacement for the SN74107? If so, that would be sweet....

 

They are the LS variety, I just checked the datasheet and they may not be a drop in replacement.

 

http://www.ti.com/lit/ds/sdls036/sdls036.pdf

 

C2iJcf9.jpg

 

I'll have a look through my stash of pulled early 1970's 74xx chips and see if I have any 74107's.

 

PM incoming...

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