Path: utzoo!utgpu!watmath!isishq!f171.n221.z1.FIDONET.ORG!izot
From: izot@f171.n221.z1.FIDONET.ORG (Geoffrey Welsh)
Newsgroups: comp.sys.cbm
Subject: Re: 6551 interfacing
Message-ID: <2483.24875872@isishq.FIDONET.ORG>
Date: 2 Jun 89 16:39:26 GMT
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 > From: daveh@cbmvax.UUCP (Dave Haynie)
 > The 1700/1750 units are C128 products.  They aren't intended for the C64,
 > and in fact a 1750 has an excellent chance of turning your C64 power
 > supply into a smoking pile of ash.  While they _may_ work on a C64, it's
 > at your own risk....
 
   My comments about the 1700 & 1750 working on the C64 may have been flippant 
and rather presumptuous about the interchangeability of accessories for the 
C128, but now that you mention it, I do know an appropriate application of 
your rule that things released commercially better work reliably: the C64 
power supply.
 
   You see, many of us who would be adventurous enough to plug a 1750 into a 
C64 threw out our C= issue power supply long ago (assuming that it was still 
working!) and replaced it (in my case with a boat-anchor device ugly as heck 
but built with devices so over-rated that it easily handled TWO C64s with 
cartridges and didn't even get hot).
 
   I know that nothing lasts forever and I do not expect power supplies to be 
immune to this, but the C64 supply is a great example of bad public relations. 
While working at the computer department of Eaton's (a Canadian department 
store, in fact the place the PETs first sold in Canada), Jay Winick (author of 
the Dircon BBS software) saw literally HUNDREDS of C64 power supplies 
returned, with their outer plastic cases MELTED. To Commodore's credit, they 
didn't seem to pose a fire hazard even in that condition, but it must not be 
confidence-inspiring to have your computer die on you and then find that the 
power supply had overheated so much that it had softened the plastic of the 
case.
 
   It would appear that the transformers in the C64 power supply were 
custom-wound, or at least sought out carefully; given the effort involved in 
that I wonder why an oversized (and difficult to find) high-current 7805-type 
device was used in stead of the much hardier (and easier to find!) LM323? In 
retrospect, several companies made (and continue to make) small fortunes 
selling C64 replacement power supplies.
 
   Please, Commodore, don't allow marginal engineering like this to happen 
again. Most of Commodore's engineering shortcomings in the past have been the 
result of assumptions that certain things would NOT be done with a particular 
computer model. I am sure that the C64 design team has been surprised again 
and again with what their toy has been made to do.
 
   Geoff
 


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