Arcade Collecting > Restorations & repair
Centipede Mini Restoration
WunderCade:
With working Centipede boards going for a pittance on eBay, is getting this board fixed just a personal crusade?
Level42:
I don't see the sense of replacing one old-bad-cheap socket for another ?
The sockets used on arcade boards I've seen so far are of the cheap kind:
Those make contact to the IC pins using "pressure", much like a PCB edge connector does. They also use lesser quality metal. So why did they use them ? Well, they were fine for as long for the games expected life-time in arcades, 2-3 years and they were cheap !
We all know they can oxidize but even worse, they loose contact because of the "pressure" is getting weaker when they get old. (Like a spring loosing it's tension).
When I replace IC sockets I _ALWAYS_ use sockets with wound contacts. You can recognize them by the circular shaped holes:
Inside of the holes, the metal contacting the IC leg is wound like a spiral. This way it has LOADS of contact with the leg. They do not rely on a "spring" tension so they cannot loose it and they are usually made of better quality metals.
Needless to say they are (much) more expensive. It's not too bad if you need a couple of sockets, but it really adds up if you need large numbers. Often the IC's I use in those sockets are cheaper than the sockets themselves.
Still, I would never use anything else.
You should really try to remove an IC from a cheap socket and then from the same socket in "wound" version..... You can _feel_ that it's better, it has a very firm grip on the chip.
The numbers you mention (the one's after the -) are an indication of the possible speed of the RAM IC.
The lower the number, the higher speed it can handle. However, I've replaced RAMs on my SW that were -10 with new versions that are -15 without any problem. It just depends on how fast the memory is accessed by the system in which it's running.
Also: if you insert a "faster" chip, the board will NOT run faster because the memory is still accessed at the same frequency.
I remember some service bulletins from Atari telling not to use certain brand of RAMs but I can't remember what brand...Think it was in the Arcade Archives somewhere...
SirPeale:
I used it because it was what I have on hand. Like I said above, I had JUST placed an order with Mouser. I'm doing this on an extreme shoestring here. A lot of time when I need a part I don't go with brand new, I scavenge them from boards I have here.
I don't think it's the socket. Possible? Perhaps, but I'd sooner think another issue.
SirPeale:
--- Quote from: WunderCade on October 11, 2008, 04:09:42 pm ---With working Centipede boards going for a pittance on eBay, is getting this board fixed just a personal crusade?
--- End quote ---
Define "pittance". So far I've got nothing but time into it. Right now money is more valuable than hobby time. And yes, I'll learn a little something as I go.
This was my first chip replacement. I knew how to do it, but I've never put the knowledge into practial use until today.
There could also have been a problem with the RAM chip from the start; I pulled it from the Galaxian board I bought from CSA3D a couple years ago. I'm pretty sure the board has issues (I've never plugged it in) because there's a chip missing. It would not surprise me if the RAM I put in there was already bad, or on the cusp of going over.
Unfortunately now I have to get some 2101s. Yes, 42, I'll get new sockets at the same time (though they probably won't be the wrapped ones unless I can get them from the same place).
Level42:
Well, there's an easy way to check if the socket is a problem: measure resistance between the leg of the IC and the soldering on the other side of the board. If they all beep out, than the socket shouldn't be the problem.
Also check the traces from the islands to where they connect to.
Tracks coming loose usually means either too hot solder iron or too long applying it. The Atari boards are good quality (esp. compared to the Wells Gardner ---Cleveland steamer--- I've worked on) so the tracks should stay put normally.
It would surprise me if Mouser didn't have the wrapped ones....
Aside from the money, there's also something called "satisfaction" in repairing a board. I've repaired my Centipede board myself and I'm pretty proud of it. Was able to trace all problems to 3 bad IC's (one in the watch-dog circuit, the LM324 (audio-amp) and one was the trackball buffer IC.
Yes I could have ordered a working board from the US, but this was so much more satisfying and I learned a great deal from it.
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