Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cwjcc!neoucom!wtm
From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.sys.att
Subject: Re: Screeching Noise & Screen Gibberish
Summary: could be a loose modem chip
Keywords: 3b1/7300 terminal gone crazy
Message-ID: <1834@neoucom.UUCP>
Date: 13 Nov 89 15:40:56 GMT
References: <1244@adds.newyork.NCR.COM>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 25


The screeching might might have been coming from the speaker, which
is located in the back of the CRT housing.  The speaker audio comes
from the modem circuitry.  I noticed on my 3b1 that there is a
white ceramic Western Electric chip in an ersatz sort of socket
(pins but no plastic surround) near where the volume control is on
the motherboard.  I believe that chip could be the trouble maker.
I don't know about all 3b1/7300 motherboards, but that socket-like
arrangement doesn't look real long on reliability.  A cure might be
to rock VERY gently under the chip with a screwdriver, lifting up a
millimeter or so then reseating the chip, finally pressing down CAREFULLY
with one's thumb.  Extreme care is advisable with that chip since
it is in a thin ceramic package and it is a custom part.

On my own 3b1, the 68010 apparently lost contact in its socket.  I
experienced a crash a while back where the machine was totally
functionless; pressing reset didn't generate the so-called lace
pattern on the screen or anything.  Removing and reseating the
68010 cured the problem.  (This happened about 2 weeks after AT&T
replaced the motherboard in my machine.  Ironically, the original
motherboard wasn't bad.)  Its been about a year and a half since
I reseated the 68010, and the machine is still running fine.


Bill