|Re: Anyone build a ZVC (Zeprom Voltage Converter)|
Message #5 Posted by Dan Grelinger on 12 July 2008, 5:40 p.m.,
in response to message #4 by Diego Diaz
Diego, Allen, Muhammad, and all,
Here is some additional information, including photos. I have loaded high resolution pictures of the ZVC at http://www.flickr.com/photos/dangrelinger/sets/72157604693293476 The original pictures are high resolution; to see the original resolution, select a picture by clicking on it, click the 'All sizes' button above the picture, and then select 'Original'. You can also download the original picture, it's 2592 x 1944 pixels.
The mystery component is labeled 221K on the top, and is to the lower left of the large 470 uF can capacitor laying on its side. The mystery component might be a capacitor, but it's appearance is different from most capacitors, and in an email communication I had with Christoph Klug, he made reference to a 'coil' (inductor?) that Zengrange had experienced failures with in early versions. But this does not look like a standard inductor either.
And yes, Diego, the voltage upconverter is "MC34063", and you suggested. I made a typographical error in my previous post. Perhaps the "mystery component" then is an inductor.
From the hand-drawn schmematic that I have, the function of the ZVC appears simply to pass Vcc from the HP-41 onto the V+ line to the ZEPROM module 'cleanly' (through a diode) unless the switch (S1) is activated, in which case the voltage upconverter supplies the necessary 12 volts to the ZEPROM V+ line for programming. An interesting part of the design is the parallel arrangement of three 1-ohm resistors to help produce what may be some sort of reference voltage for the upconverter chip. I'll reproduce the schematic I have into something that I can post.
It certainly may be possible to build a much simpler circuit today. If voltage upconverters have gotten simpler to design circuits around, perhaps all the 'peripheral' components may not be needed?
The PCB is two-layer, front and backside. It is not copper though, I don't know what the metal is, but it is also used as the contact material for the ZEPROM to attach to.
Thanks for everyone's help!