EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: Daxxin on April 10, 2016, 02:38:21 pm
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getting troubles with very very old scope videocard (37 white thin vertical lines) checking
the ram chip DIP18 M5M4416p something look weird to me but maybe its normal someone can explain
why i get this tooth saw 400mv between one pulse and next? it is normal?
not all the pin like this some data have pulses very clear , example from pin 3 i get this.
(https://s24.postimg.org/zbw16bwph/wa12.jpg)
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Most likely a clock appearing as noise on the data line, caused by a combination of scope ground lead inductance and the internal bond wire length in the chip and processor. Try measuring again minimising ground lead distance and it should vanish, or drop in amplitude. As it is a lot less than a valid logic low or high it should not be a worry. Vertical white lines though do tend to say there is either a ram address fault or a faulty chip. Check for dry joints on the chips and if they are in sockets remove and reinstall them to clean the pins. You could also have a socket with a broken pin, which is hard to trace as they break inside the plastic housing.