Article-I.D.: vaxwalle.748
Posted: Thu Apr  2 14:13:14 1987
Date-Received: Sat, 4-Apr-87 16:33:38 EST
Distribution: na
Organization: Varian, Walnut Creek CA
Lines: 94
Keywords: crash
Xref: utgpu comp.sys.ti:15 misc.kids:916



	Thank you to all who sent me your ideas so quickly.

I replaced with a Radio Shak power supply (good design, inexpensive $5)
I cleaned & adjusted the connectors, I sprayed Freon etc...
Unfortunately I still have the problem after trying all the suggestions
and the problem occurs also in TI Basic w/out a cartridge .

I plan on exchanging it with TI since I don't have too much time to
mess with it anymore.
	One may send the defective unit with $36.50 to receive in
exchange one reconditioned unit with 6mos warranty.
	Mail to :  TI repair & service
		   2305  N. University ave.
		   Lubbock, Tx  79408
			phone:800-TI CARES

	PS: I tried to reply to some of you directly but our outgoing
	mail is acting up (it is Spring in the land of Vax-droids!).


Here is a summary:

Idea 1:
I had the same symptoms several years ago on an older 99/4A.  I took it
in to my local TI service center, and for $39 they gave me a new 99/4A.
They said it was caused by the Graphics chip (don't know the number).

I'm having similar problems with the newer box.  I am in the middle of
the 4th level of Parsec when the world stops and the only way I've found
of recovering is to power down.  Reseating the cartridge in my machine
to the far right of the cartridge slot seems to help.

I thought it was heat related too, but if I power down and back up right
away, the system still runs, so it can't be only related to heat.  I did
install one of the high efficiency supplies that Radio Shack sold a
while ago, but didn't see a noticable change.
I am beginning to suspect a connector intermittent for my problems, and
am considering hard wiring some connections.

Good Luck,
Mike Stevens

Idea 2:
     Sounds like your problem is the power supply.  These are prone to
overheating; the power supply design leaves much to be desired.  The
+12V regulator powers both the +12V and the +5V for the CPU box.

     A couple of years ago Slug, my faithful 99/4A, loaded a program
from tape, then let out a peircing shriek and the screen went bananas.
     Radio Shack sells a supply board for the 99/4A that fits into the
cabinet after a little juggling.  It runs a lot cooler, and has worked
very well in Slug.

				Hope this helps...
				Kchula-Rrit


Idea 3:
I assume you are having the problem during the use of the cartridge software-
If so, the problem is easy to fix.  It's the edge-connector the cartridge plugs
into inside the console.  Open up the console, and take out the main board.
on the top side of the main board is theadapter card for the cartridge.  It
consists of an edge connector and a card edge which plugs into another connector
on the main board.  What has happened is one of the following:
a) the card edge is loose and not staying firm on the main board,
b) the edge connector is worn out.

If the problem is (b), the solution is easy: just unsolder the old connector
and replace it with a new one.  If it's the connector on the main board, I'd
consider getting a replacement unit from TI, as messing around with soldering
that board is probably more trouble than it's worth.  

Good Luck!!
Steve Ward
satisfied 99/4a owner

Note: Others responded with similar suggestions regarding the connectors.

Idea 4:
What you want to use is some freon cold spray, its used specifically for
electronics.  Let the machine warm for say 3 or 4 minutes, then spray the
general area of chips that you suspect.  The chip or chips that are running
hot will quickly disappate the freon, and walla, you know which chip has
thermal runaway.

Brian Douglass

-----------------------------------------------------end
-- 
tom cao     (415) 945 2157                
Varian Instruments 2700 Mitchell Dr.  Walnut Creek, Ca. 94598
{zehntel,dual,amd,fortune,rtech,lll-crg,rtgvax,ptsfa,csi}!varian!vaxwaller!tom