Fat40 RAM problem?

From: A. Fachat <afachat_at_gmx.de>
Date: Fri, 29 Aug 2014 00:53:55 +0200
Message-ID: <4275255.qDcX5vBoA2@euler>
Hi there,

I've analyzed the RAM problem on my Fat40 a bit more. I've recorded the broken 
addresses - which are stable - and measured the RAM chip in question (UA16 ) 
with the scope.

See https://www.flickr.com/photos/afachat/sets/72157646409152698/

What looks interesting is that the data I/O pins of the RAM even stays high 
when I write a zero into it! I.e. either the RAM is broken and pulls the line 
high, or the driver (or something else) is broken. However, I cannot see why 
the combination of address bits should create a driver failure. Measuring 
another chip in the same bank shows the corresponding data line going low as 
it should, as well as the same chip with another address.

Anyway, I've ordered a 4116 RAM replacement and will replace the chip to see 
how it works out.


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Received on 2014-08-28 23:00:02

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