Faulty ram slot

[Translation]

I bought used this 500mhz ibook. Everything works fine. I tried to upgrade
the ram with 4 different ram sticks. 1 128 one from a wallstreet, a 256 from
a Pismo, a 256 from a TiBook, and today, and original apple 256 ram stick
pull from a 14 inches iBook. None of them work. I go to get info and system
profile and only shows the default 128, the slot as empty. At first I
thought the ram was not the appropriate, but after today I think that the
slot is the faulty one. Has anybody heard anything like this before? I read
all the posts here and no explanation so far. can a faulty ram slot be
fixed/replaced without paying apple 350 for a logic board swap?

Help. 

Thanks to all