Computer Saver from Ray Carlsen

[RobertB]

     Ray Carlsen, veteran Commodore repair technician, is now selling Computer Saver (an improved version of his original Computer Saver, the schematic of which had been on his website for years).  Like the original, his new Computer Saver functions as a voltage limiter when plugged in-line between the C64 and the C64 power supply.  Read what Ray says about his product --

---------------- Original Message -----------------
From:    "Ray Carlsen" <rcarlsen(at)tds.net>
Date:    Fri, June 21, 2013 11:53 pm
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Hi,

Photos of the construction of those savers are on my site -- http://personalpages.tds.net/~rcarlsen/cbm/c64/SAVER/EXTERNAL/

    AN EXTERNAL "COMPUTER SAVER" PROTECTION DEVICE FOR THE C64

      This shows a small run of the Computer Saver I designed. It is made to be installed between any C64 and its power supply. The two LED's on the Saver case are indicators of the PS status. The LED on the left monitors the 9VAC from the supply and it should be on all the time the PS is plugged in to AC power, whether the computer is on or off. The other LED (marked "failsafe") is normally off. It only comes on if the PS fails due to a shorted internal regulator. That fault is what damages chips in the computer, most often the RAM. Since there is already an LED on the computer case which
monitors the regulated +5VDC, one on the Saver was considered unnecessary.
      The cost of the Saver is $50 US. That price could be reduced somewhat with a larger production run, but unless there is greater interest in this device, I'm not ready to tool up for that. More than half that amount was spent for parts, including shipping. Any time something is hand-made and parts are individually purchased, the price of the end product will be higher than people expect. The construction of a stand-alone device is normally higher than the same circuit built into a computer such as the C64. That's due to the added expense of a case, cable wire and connectors as well as the added time it takes to assemble the device. There are few shortcuts, so the price is firm.
      One version of this device has been seen for sale on the Internet, but the builder likely didn't consider one thing when constructing it. Most importantly, the "trip" point of the Saver is critical. That is the exact voltage level at which the device cuts off power to the computer. Because of variable tolerances of some of the components, the trip point must be manually set with an accurate voltmeter and variable bench power supply. This setting is done as a last step after the device is built. If it is set too high, the computer is still at risk, and if too low, the device may cut power with a normal power supply that has a slightly abnormal but acceptable output level during a "no load" condition such as when the supply is plugged in to AC power but the computer is turned off. Keeping those voltage limits in mind, I found the optimum trip point to be between 5.3 and 5.4 volts DC. RAM chips have an absolute maximum rating of 5.5 volts, so the protector -must- be set below that value.
      Because the protectors LED's are on its case, I decided to make the cable between it and the computer rather short, about one foot long, so those LED's can be monitored. If desired, that cable can be made longer so the protector is off the desktop. However, very long cables will reduce the voltage at the computer since it draws nearly one Amp in normal operation. The short cable seemed like the best arrangement.

Ray

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          See Computer Saver on exhibit at CommVEx,
          Robert Bernardo
          Fresno Commodore User Group
          http://videocam.net.au/fcug
          July 27-28 Commodore Vegas Expo v9 -
          http://www.portcommodore.com/commvex

[RobertB]

     Ray is down to a few Computer Savers left for sale.

          Truly,
          Robert Bernardo
          Fresno Commodore User Group
          http://videocam.net.au/fcug
          The Other Group of Amigoids
          http://www.calweb.com/~rabel1/
          Southern California Commodore & Amiga Network
          http://www.sccaners.org

[RobertB]

     Ray Carlsen now offers three versions of the Computer Saver.  There is the $25 Computer Saver module that a user can install in their own computer, there is the $35 Computer Saver cable (without LED indicators) version, and there is the $50, original, case-mounted Computer Saver (with LED indicators).  To read more about Computer Saver and to see pictures, go to

          http://personalpages.tds.net/~rcarlsen/cbm/c64/SAVER/

               Truly,
               Robert Bernardo
               Fresno Commodore User Group
               http://videocam.net.au/fcug

[RobertB]

     Ray Carlsen now has one webpage that lists all his newly-improved Computer Savers and adapter cables for Commodores.  Go to

http://personalpages.tds.net/~rcarlsen/cables.html

The current prices are listed there.  Check out the new mid-line Computer Saver for the Commodore Plus/4.

          Merry Christmas,
          Robert Bernardo
          Fresno Commodore User Group
          http://www.dickestel.com/fcug.htm