New Life Games LLC
General NLG Chat => General Chat, Slot Shop **Tech Talk** Welcome wagon and other stuff. (Off-Topic Post Welcome) => Topic started by: Buzz on May 18, 2014, 05:24:01 PM
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Raymon or Kevin you will probably need to move this to the proper topic.
Here lately I've been modifying the legs on eproms. We all have this same problem of breaking a leg off. Now me, I have a eprom burner so if I break a leg off it's no big deal I'll just make a new chip. But most of our members don't have that luxury and they have to worry about it. Over the years I have found the leg will almost every time break about half way down or will break right up next to the black part of the eprom. I don't know are care what the black part is made out of and I'm going to call it the back. Now in the case where the leg breaks half way down this is a easy fix. I keep some old no good eproms I call donor eproms. Bend the whole leg from the donor chip back and forth until it brakes loose. Put some flux on the broken leg of the good eprom and flux on the leg from the donor. A little of solder on both legs, holding the donor leg with a pair of pliers, position it over the broken chip leg and just touch it with a HOT soldering iron. Your done. Now if a leg breaks off up next to what I called the back your screwed most of the time. I do have a way to recover the files from a chip, but never had much luck repairing one.
OK this is what I started this thread for. and I've had pretty good success so for. I take a perfectly good eprom, put soldering flux on the top part of all the legs ( next to the back ) then drag a HOT soldering iron the full length of the chip. Then load the soldering tip up with solder and drag it the full length. When I say drag, go slow enough for the solder to flow onto the legs but not so slow that the eprom is going to be over heated. ( you can move the iron pretty fast ) If you want to do a better job, make a second pass with the iron this time about half way down the leg. Just make sure you have solder on all the legs and up next to the back you didn't get two legs bridged together. If they are bridged just touch them with a hot iron and the solder will flow to one or the other.
This whole soldering process will take less than a minute, but you can't believe how much stronger the legs feel. It's like the legs have been reinforced.
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Thats a good idea.
Thanks for sharing.
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Not a good idea.
When you put the EPROM into a socket it is no longer a tin on tin connection but a tin on lead connection.
The lead oxidizes causing a bad contact between the socket and the EPROM.
Look up dissimilar metal contact and see what happens.
Can't tell you how many boards I get into the shop where someone has tinned some pins with solder and simply replacing the tinned leads solves the problem.
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what was lead solder was a alloy of tin and lead, lead was used to lower the melting point.
Then they changed the alloy to remove the lead
the Solder I have is:
Tin Sn 99.2%
Silver Ag 0.3%
Copper Cu 0.5%
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Ah, a ROHS by any other name. Should have mentioned that tin/lead solder should not be used.
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If you look at most Chip leads they look oxidized and tin also oxidizes.
At the voltages and speed that most EPROM's use, applying any solder to the leads is not going to make a difference
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But it has. I have had to fix such problems over the past 40 years.
Someone will solder on a broken leg and get solder down the entire leg, years later the board ends up in the shop and the thing causing the board not to work is the leg with solder on it and the weak signal or voltage on that pin caused the board to fail.
Or someone will tin the leads of a molex header and years later the connection between the connector and header will fail.
Or someone will tin the gold or tin contacts on a edge connector.
I learned about this fault in a NASA soldering course many years ago and have seen it in action.
I also learned that cleaning the excess solder flux off of a connection prevents circuit failure but not to many techs follow that procedure.
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I learned about this fault in a NASA soldering course many years ago and have seen it in action.
Does anything oxidize in a vacuum? :Scratch-Head:
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What I do with damaged EPROMS:
Use a low profile IC socket; plug the chip into the socket, bridge the bad pin with a small piece of wire to the socket and then solder it. There is always a very small piece of the original pin left where it enters the molded chip. If your chip is a ceramic chip, you can use a Dremel tool with a diamond bur to break into the cement between the ceramic layers, exposing a very small piece of the tab. A solder bead there will be enough to attach a fine piece of wire.
Once it's inserted into the socket, you're ready to go. Plug that socket into the board's EPROM socket - or preferably - into your burner where you can load its file and burn another chip.
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I do the same thing.
If I have a bad EPROM that won't program or read properly I cut all of it's pins off (as close to the body as possible) and save them.
When I have a EPROM with a broken pin I tack solder one of the salvaged pins where the pin broke off.
The Dremel works good to expose enough metal to get a wire or pin soldered to where the broken pin is.
If you have ever had a EPROM break in half and can see the metal under the top cover you will see there is plenty of metal to work with before the actual chip is encountered.
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GI and TI made mask ROMs from the 80s were notorious for breaking pins. They used steel pins that were silver plated and they are a PITA to deal with. I usually replace them with EPROMs when I run across them.
Namco used the same damn material for custom ICs used in Xevious, Galaga, Pole Position, Bosconian, Dig Dug, and many other games. They like to break too and are hard to find at times. You take a sharp box knife and scrape the crap off what's left of the leg, tin it, and solder a donor leg from another chip to it.
If the pin broke off at the body of the chip you can use a Dremel tool with a grinding wheel to grind back the black epoxy body of the chip on top of where the pin goes into the body. Relieve it about 1/16" to 3/32" deep then tin the exposed leg. Take an EPROM that has a narrow body and a leg that is bent and take off the leg as close to the body as you can. Insert the custom chip into the socket, tin the underside of that donor leg , then slide it down into the socket to where it's making contact with the exposed metal on the chip body. Push the leg down lightly with the soldering iron to solder the leg into perfect position. POOF. You fixed the custom IC.
If multiple pins broke off you can use a machine pin socket to fix the chip. Scrape the crust (rust and tarnish from the silver plated steel leg) off the outside surface of the legs of the chip, put it in the machine pin socket, and solder the pins to the socket individually, being careful not to melt/deform the plastic around the pin too much. When finished, plug the custom chip/socket combo into the socket on the board and you are done.
:)
Can't tell you how many times I've had to do that to save a hard to find custom IC!
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Raymond I think you need to go back and read replies #2 and #6 When I started this thread I thought solder was a good thing but now after reading this thread I'm not so sure. I mean I sat here tonight taking a real good look at a MPU and all those devices soldered to it and if what I've just read is true all it is is a huge pile of oxidization. I'm scared enough that I'm going to start wearing rubber gloves if I'm going to be handling a board. You touch a MPU with your bare hands, go take a leak and with all that oxidization, your pecker might fall off before you get back to the work bench.
The one good thing about someone being my age, and that is I'm not expected to have a very long memory. I'll bet by tomorrow or the next day I will have forgotten all about this thread and I can go back to tinning the eprom legs like I said at the begining.
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Ha! mine fell off years ago.
Or do we need to start a new thread for this topic?
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If I was worried about such things I would not have ever started soldering at all.
I started when I was 15.
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Neonkiss, since the definition of a vacuum is "nothingness",
nothing will oxidize in an environment with no oxygen.
Buzz, at our age, the second thing we lose is memory;
but damn, I can't remember what the first thing was... :Scratch-Head:
If the board is an old one with lead-alloy solder, I use the same old 60/40;
that's called "restoration".
If it's new enough to be using lead-free solder, I give it to my son-in-law,
'cause I'm not interested in anything that new. That's called "dump it on the kid."
If in the meantime my pecker falls off, I'll be happy if I remember what it was for;
and overwhelmingly happy if my WIFE remembers what it was for :applause: :applause: :applause:
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Buzz,
If you read my reply, I talk about soldering a donor pin in place of the broken one. Nowhere did I say to solder the whole pin. I just solder the tops where they bond together with the hot solder.
RJ
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can you solder a new pin on the chip
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It can be done, but very carefully. First, you grind away the ceramic surrounding the broken pin, using a Dremel tool with a diamond grinder ball, just enough to be able to add a dot of solder. Then you place the EPROM in a ZIF socket, and add a small strand of wire to the empty socket terminal. Once the lever locks the pins and the wire down, you add a small bead of solder to that wire, at the exposed broken tab. Place the ZIF socket in your programmer, and download the image.
You're all set. If you can't reprogram a new chip, keep the old one in the socket and insert the whole assembly into your PC board.
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We keep a collection of pins cut off of bad IC's, cut the pins flush with the body of the IC then clean the exposed broken pin and add a bead of solder.
Hold your replacement pin at the tip with a pair or needle nose pliers and heat it with your iron.
When hot enough lay it on the bead of solder and heat until the solder melts bonding the two pieces together.
Trim the end of the attached pin to match the length of the remaining pins.
If you accidentally get solder all over the replacement pin remove it and start over with a fresh pin.