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From: bryan@cs.utexas.edu (Bryan Bayerdorffer @ Wit's End)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Patches done to the B2000 ?
Message-ID: <373@mohawk.cs.utexas.edu>
Date: 21 Jun 91 17:41:34 GMT
References: <1991Jun21.021132.23327@trl.oz.au>
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In article <1991Jun21.021132.23327@trl.oz.au> aduncan@rhea.trl.OZ.AU (Allan Duncan) writes:
=-
=-Has anyone got the details of what was done between the board revisions?
=-Mine is about 4.2 or 4.3 (I'm not pulling the lid off just to look while
=-on-line:-))
=-

Here's the short version, summarizing the procedure given in Issue #26, section
3-2.1 (Jul-Sep 89) of the Commodore service technician's update, "TechTopics:"

A2000 field upgrade to rev 4.5:

1. Remove if installed:  R901, C917, C902, C910, C911, C905, C908, C230, C240

2. Install 1.3 Kickstart ROM

3. Install RP904, RP905, RP906 only if U205 and U206 are 74HC244 type ICs

4. Add .01uF ceramic cap on solder side from pin 12 of J300 to nearby ground
pads. 

5. Add 3.3K ohm, 1/4W resistor across pins 11 and 20 of U605. [Note: Dave Haynie
recommended 1K ohm resistor in a previous article]

6. Add 470 ohm, 1/4W resistor from cathode of D800 to second pad from the left,
under CN605.  (Already installed as R1000 on rev4.3 and above)

7. If R5719 not present, add 470 ohm resistor between Vcc and CPU side of R106.
Use pad located to the right of U100, and the pad on the ground trace running
under pin 14 of the 68000.

8. Replace Toshiba GARY (U102) with MOS GARY.



DISCLAIMER:  While making these modifications eliminated some problems with my
A2000, I take no responsibility for the results obtained by anyone else
following the above procedure, nor for any inacuracies or errors I may have
introduced.  For a full description of the procedure, obtain a copy of
TechTopics #26 from a Commodore dealer.  In addition, it may be that the
procedure was revised in a later issue.


That said, let me mention that the most important step in *my* case appeared to
be the replacement of the Toshiba GARY with a MOS GARY.