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From: hanes@raksha.eng.ohio-state.edu (Mark D. Hanes)
Newsgroups: comp.sys.amiga.tech
Subject: A500 hardware problem con't...
Message-ID: <3967@quanta.eng.ohio-state.edu>
Date: 18 Jan 90 22:15:17 GMT
Sender: news@quanta.eng.ohio-state.edu
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This is a follow-up post to my previous post concerning
a green screen on power-up along with a blinking power
LED (11 blinks, pause, and repeat).

Does anyone out there know how the RAM's are checked
on power-up.  Are they written to and then re-read
for verification?  Or what?
 
The problem does not seem to be a mis-seated Fat Agnus.
It has been re-seated, had the connector pins bent out 
and re-inserted, even replaced the socket itself.
All custom chips have been checked by swapping one
at a time with known working ones.  
The clock signals seem ok, and the refresh signals
coming out of Agnus seem ok, as well.
The problem is not a short with the RF shield either,
nor a short between the board and the disk drive.

Thus, I think the problem is a defective 256kx1 DRAM
chip.  I was curious how these are checked on power-up
in order to get a better idea of what is failing.

If anyone has any additional suggestions or an answer
to the above question, please e-mail me at
   hanes@phao.eng.ohio-state.edu

   Thanks again,
   Mark.


-=-
Mark D. Hanes
hanes@phao.eng.ohio-state.edu
Electrical Engineering
The Ohio State University