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From: grr@cbmvax.UUCP (George Robbins)
Newsgroups: comp.sys.amiga
Subject: Re: CBM and upgrade paths
Message-ID: <2721@cbmvax.UUCP>
Date: Wed, 11-Nov-87 07:47:08 EST
Article-I.D.: cbmvax.2721
Posted: Wed Nov 11 07:47:08 1987
Date-Received: Fri, 13-Nov-87 23:46:24 EST
References: <8711040542.AA29099@violet.berkeley.edu> <2696@cbmvax.UUCP> <21704@ucbvax.BERKELEY.EDU> <777@ritcv.UUCP>
Reply-To: grr@cbmvax.UUCP (George Robbins)
Organization: Commodore Technology, West Chester, PA
Lines: 38

In article <777@ritcv.UUCP> ptp6186@ritcv.UUCP (Paul T. Pryor) writes:
> In article <21704@ucbvax.BERKELEY.EDU> bryce@hoser.berkeley.edu (Bryce Nesbitt) writes:
> >
> >The A501's real time clock cannot be easily calibrated.  The
> >case is soldered shut and there is no access hole to the 
> >trimmer capacitor.
> 
> Agreed. Now, it is a simple matter of drilling a hole in the cover.
> The bad new is that in order to twiddle the trimmer cap, it is
> necessary to remove the A501 from the A500. The other alternative
> is to remove the top case, and about once a week, twiddle the
> clock (first moving the keyboard out of the way). When the clock 
> is back to specs, put the top case back on. This would kill the
> warranty for both the A500 and the A501 :-(.

Ugh, you weren't supposed to mention that!  8-)

There really should be a couple holes over the trimmer cap and TP3 to
make adjustment simple, but I was still busy trying to get the board
layout done and thru FCC to keep a close eye on the mechanical people
that did the shields.  Maybe we can do something about it, but it would
take months for the holes to show up in your dealer.

Since the clock is battery powered, you can adjust it outside the
machine, however the test point is disabled and you would have to
measure the frequency directly at the crystal.  Unfortunatly, you need
a special inductive or ultra-low capacitance probe for this, since any
loading at the crystal will shift the frequency.

This is one of those situations where there does't seem to be a real
elegant solution that wouldn't jack up the price of the expansion or
require unusual test equipment.  At least they are adjusted at the
factory.

-- 
George Robbins - now working for,	uucp: {ihnp4|rutgers|allegra}!cbmvax!grr
but no way officially representing	arpa: out to lunch...
Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)