Hi Leonard.

23-May-03 16:36:14, Leonard Erickson wrote to Jasen Betts



 LE> This whole unit is way too small for most of that stuff. The power
 LE> comes in via a "typical" coax power jack. And while there *is* a
 LE> diode and a few *small* capacitors, I doubt it's doing anything
 LE> fany.

 LE> Remember, this gizmo is about the size of a deck of cards.

a DC-DC converter could be around the size of a cube of sugar....
probably an oscilator driving a diode pump given the power requirements,
(that's how the MAX chips do it)

small caps?, a pair of 4.7uF caps would be plenty plenty for a DC-DC converter,
(or smaller - it really depends on the running frequency of the device)
A doubler would want something a little larger 47uF maybe.

another way to do it woauld be to supply the device with 24Vdc and treat
it as a +/- 12 and derive the +5 volts from that...  the giveaway with
that setup would be a direct connection from pins 1 and 14 of the 1488 to
the powersuply socket

otoh if there's a direct connection from pin 7 of the 1489 to the
powersupoply socket that'd most likely be the negative pin given that a series
regulator is being used... with that setup I'd expect a  12V supply with
a diode pump generating the -12 supply like this:

 +12 in >-+--------------+----------------------------> 1488 pin14
          |              |
          `--[REG]-------)----------------------------> 1489 pin 14
               |         |
               |   (oscilator)--||--.      .----------> 1488 pin 1
               |         |          |      |     c1
               |         |   .--|<--+--|<--+---||--.
               |         |   |                     |
  0V in >------+---------+---+---------------------+--> 1489 pin 7

  REG is that LMxxx chip you mentioned earlier, oscilator could be
  anythiong  maybe a 555 (or 556 etc) chip, maybe sometjiong based
  around discrete transistors, maybe a logic chip. maybe derived from
  one of the processor's  address lines...

  look for the arrangment of diodes and capacitors shown,
  OTOH  C1 could go to the +12 instad of the 0V

if you find it give the device 12V DC as shown.




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