General NLG Chat > General Chat, Slot Shop **Tech Talk** Welcome wagon and other stuff. (Off-Topic Post Welcome)

Eproms (Fixes)

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Buzz:
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.

laneman:
Thats a good idea.
Thanks for sharing.

Badbaud:
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.

foster:
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%

Badbaud:
Ah, a ROHS by any other name. Should have mentioned that tin/lead solder should not be used.

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