🚀 go-pugleaf

Wayne Thompson writes:
> > Is there *any* way to take the c64 and use it in a car?
> > Does it really *have* to be getting it AC?
.
.

> A friend of mine is using a vic-20 in his car. He clipped the input cord
> between the transformer and the computer and added a cigarette lighter
> plug to it. NO, it doesn't require AC. the drawback is that the machine
.
.
	The new c64s mgiht be different, but an older one that I
had several years back really did need to have the 9v ac going in.
Not having the schematic at my fingertips, I might be a bit off,
but, the a.c. goes into a half-wave voltage doubler to make 12v or
something similar.  Seems to me that it was used to power the video
modulator or something like that.  Perhaps, it was -5 volts for
the DRAM chips.  With some careful work, you
could circumvent the need for the a.c. input, and substitue an
outboard power supply.  The change would not be easy, and would
cause the "user interface" pins not to meet spec.  Note that things
such as rs232 interfaces that plug into the user port might be
expecting the 9 v ac so that they can manufacture their own +/- 12
volt supplies, or whatever.

	Also, please note that [at least in the c64 I had] that the
5 volt regulator is in the brick-on-a-cord, and that sticking 12 v
into the computer would charbroil lots of items.

	It's close to essential to have the schematic before
attacking the hardware of your computer.  Get the Sams manual and
check out the diagram in the back.  Note that the c64 motherboard
has been through upteen revisions, thus the actual circuitry in
your computer is probably different.  The main differences are that
the newer '64s have an 8-pin video jack and the older ones like
mine had a 5-pin jack.  (The newer video has the separate luma line
and chroma lines to work better with the 1702 monitor).  I think
some of the PALs are different too.  I think the power supply
remains largely unchanged.

	Speaking of the brick-on-a-cord, how many have you guys out
there been through.  I used to blow them up every couple of months.
The annoying thing is that it was usually the little fuse potted in
the goop in the brick.  Only problem was that you couldn't change
the fuse without breaking other stuff in the goo.  Dumb design.  I
was quite pleased to see that the c128 has a user-replacable fuse
on the bottom of the brick!!!

	Speaking further of the brick...  Another annoying property
is, several times the output of the 5 volt in the regulator
increased in voltage.  The increased voltage would then take out
the SID, which seems to be quite sensitive to too much juice.  The
brick-without-the-fins was a partiularly malevolent design  (w/o
fins weren't potted on the inside).  All this leads me to say that
you ought to be very careful about the quality of 5v that you stick
into your c64.  Operating in a car with dangers of alternator load
dumps (although unlikely) could shoot as much as 90 volt spikes
into the box powering your computer.  Some time, take a look at a
decent car radio (a computerized one is even better) and look at
all the little tricks that are done to protect it from zapping!  I
have a computer radio in my car, and it ocassionally gets confused
and does weird stuff, although in ~4 years it has not forgotten the
station settings.

Bill Mayhew
Div. Basic Medical Sciences
Norhteastern Ohio Universities' College of Medicine
Rootstown, OH  44272  USA   (216) 325-2511
wtm@neoucom.UUCP  (...!allegra!neoucom!wtm)