From: fc0v+@andrew.cmu.edu (Franklin Chang)
Newsgroups: sci.electronics,comp.sys.cbm,comp.robotics
Subject: Commodore help thanks
Date: 14 Apr 92 07:34:29 GMT
Organization: Freshman, Math/Computer Science, Carnegie Mellon, Pittsburgh, PA

Thanks to all who responded to my call for commodore help.
The solution that we ended up using was a even larger hack than the
solutions we were sent.  We hooked up an power inverter (the kind that
you use to watch tv in your car), to our 12 volt supply.

The original post went like this
>Hi,
>  I was wondering if anyone knows of a simple hack that will allow the
>commodore 64 to work off dc battery supply.  I've heard that the
>computer uses the waveform off the ac powersupply as a timer.  Recently
>someone posted a solution to this problem, but it required a 60 hz (not
>Mhz) oscillator and I'm at a lost to find a 60hz oscillator.  

Here is a list of what people said.

From: Danny Stark <stark@ug.cs.dal.ca>
To: fc0v+@andrew.cmu.edu
Subject: Re: Commodore help
Date: 	Tue, 7 Apr 1992 01:00:10 -0300

 You could try converting a dc supply to a full 120AC and feed that to
the Commodore power supply.  I can't remember the name of the circuit, but
I've seen such things designed to run 120AC stuff off of a car lighter.
	
Date: Tue, 7 Apr 92 08:31:40 EST
From: Scott Dorsey <kludge@grissom.larc.nasa.gov>
To: fc0v+@andrew.cmu.edu
Subject: Re: Commodore help
Cc: 

In article <Yds=uYG00VolEnD0oe@andrew.cmu.edu> you write:
>Hi,
>  I was wondering if anyone knows of a simple hack that will allow the
>commodore 64 to work off dc battery supply.  I've heard that the
>computer uses the waveform off the ac powersupply as a timer.  Recently
>someone posted a solution to this problem, but it required a 60 hz (not
>Mhz) oscillator and I'm at a lost to find a 60hz oscillator.  If any can
>help, it is fairly urgent.  Our robot is going to a competition on the
>Wed 8th.

Digi-Key sells a nifty chip from National Semiconductor that takes a
colorburst crystal and produces a TTL-compatible 60 Hz output.  They can
probably fed-ex you one by tomorrow, so all you have left is getting
9VDC into the regulated side of the supply.
--scott

Date: Tue, 7 Apr 92 12:55:26 EST
From: kempga@nextwork.rose-hulman.edu
To: fc0v+@andrew.cmu.edu
Subject: Emergency Oscillators

If a 5-volt square wave will do, you can make an oscillator by  
connecting a resistor and a capacitor across the terminals of a  
Schmitt-triggered inverter:

             R
       +---/\/\----+
       |           |
       |    C      |
       +---| |-----+
       |           |
       |   |\      |
      -+---| >O----+---- output
           |/
          7414 or
          74LS14


The frequency is around 1/RC.  You would be best served by using a  
variable resistor and manually tuning the frequency using your  
favorite technique (o-scope, frequency counter, etc.).

If you had infinite time and money I would suggest you build a real  
RLC oscillator but judging from your post this is not the case.  I  
hope this little bit of electronics first-aid helps.  Good luck!

--
Greg Kemp
inmate, Rose-Hulman Institute of Technology
Terre Haute, IN
Internet: kempga@nextwork.rose-hulman.edu

Date: Tue, 7 Apr 92 17:07:48 -0700
From: John Whitmore <whit@u.washington.edu>
To: fc0v+@andrew.cmu.edu
Subject: Re: Commodore help
Cc: 

In article <Yds=uYG00VolEnD0oe@andrew.cmu.edu> you write:
>Hi,
>  I was wondering if anyone knows of a simple hack that will allow the
>commodore 64 to work off dc battery supply.  I've heard that the
>computer uses the waveform off the ac powersupply as a timer.  Recently
>someone posted a solution to this problem, but it required a 60 hz (not
>Mhz) oscillator and I'm at a lost to find a 60hz oscillator. 

	Just use a '555 timer as an oscillator; accuracy is not
terribly important here.  Capacitor-couple the output to pin 12
(or is it pin 13?  the one that isn't connected to +5V) of U27.

	You will also lose the +12V power and the +5V that drives
most of the video circuitry (which shouldn't hurt, in your application).


	John Whitmore

Date: Wed, 8 Apr 92 18:02:41 EDT
From: rbc@engr.ucf.edu (Robotics Club)
To: fc0v+@andrew.cmu.edu
Subject: Re: Commodore help
Cc: 

don't know if this is in time......

okay, this is kinda "bad", but you might need it.

Take 5v, plug it into the right pin (uh, correct pin),
now, drag up the schematics of the 64, look at where the
9Vac comes in, some where in there, the 9vac gets converted
to 12vdc, or close to that, push 12vdc into the 12vdc area.

voila, instant power supply, the 12vdc is not needed by anything
except the video display I think.

I cannot be responsible for what i have written because 
1) I am a cs major.
2) I don't have any of the C64 schemtics on me
3) I can't take the time to back trace the wiring on our computer.
4) Revisions differ greatly.

I think the 12dvc is going to a 7812, I am not sure what that it.
but on our machine it is soldered onto what is labeled as pin
2 (far right) on a transistor (tip 120?) looking package. 
(far right is with the labeling facing you).

This works for our computer Copyright 1983 on the motherboard,
and I have seen that it will work for the new C64s with reduced 
parts.

Gotta go, tell me about your contest, Wouldn't be the SAE Walking
Machine Decathlon in NC state would it? I hope to be there,
but sadly, without a robot.

eric
wampner


** Frank's note: Yes the contest was the SAE Walking Machine Decathlon**

Date: Thu, 9 Apr 92 13:11:26 PDT
From: walsh@optilink.com (Mark Walsh)
To: fc0v+@andrew.cmu.edu
Subject: Re: Commodore help

fc0v+@andrew.cmu.edu (Franklin Chang):
> Hi,
>   I was wondering if anyone knows of a simple hack that will allow the
> commodore 64 to work off dc battery supply.  I've heard that the
> computer uses the waveform off the ac powersupply as a timer.  Recently
> someone posted a solution to this problem, but it required a 60 hz (not
> Mhz) oscillator and I'm at a lost to find a 60hz oscillator.  If any can
> help, it is fairly urgent.  Our robot is going to a competition on the
> Wed 8th.

I have a friend who does this.  A square wave will do.
Use a 555 timer, the databooks will show you how to
figure the time constants, and it will cost you about
a dollar.

Cheers -- Mark -- KC6RKZ


***************************
   fc0v@andrew.cmu.edu
     Franklin Chang
 Carnegie Mellon University
***************************