DSP CARD 4 assembling notes

Since the time when DSP4 kit has been released, some
errors were found in construction documents and software.
Corrections are:
     1.Inductor L5 must be removed and plain wire must be
       installed instead (without this modification the
       Codec will not operate at all!)
     2.In the schematics the number of turns of the
       toroid T1 is wrong, right value is 38 turns.
     3.Better IC protection can be obtained, if the
       protection Zener V5 is replaced with 5V1 type,
       also a fuse (fast) is highly recommended at the
       power input (7-16V).
     4.Wind the transformer as following:
         The transformer has two windings, the primary
         uses diam. 0.5 mm and secondary 0.3 mm wire.
         These diameters are not very critical, the wire
         should be thick enough to minimise losses and
         thin enough to fit on the toroid. The number of
         turns both in primary and secondary is 38 if
         Amidon FT50-61 toroid is used.
         
         The small switcher generates a lot of
         harmonics. To put the most of those harmonics
         in the load, the transformer must be have
         wideband capabilities. The coupling between
         primary and secondary isn't 100%. Practically
         you experience this as not ideal coupling as
         leakage inductance. The leakage inductance
         introduce series impedance in the transformer.
         When there isn't enough damping in the circuit,
         it's ringing on the fast switching. Ringing
         generate a lot of RFI and can destroy
         semiconductors.
         
         The 2 transformer windings start both near one
         of the long sides of the printed circuit board
         and run parallel the short sides of the board.
         Glue after test the transformer with hot glue
         to the printed circuit board.
         
         A good transformer for the DSP Card 4 can be
         wound by winding the primary and the secondary
         at the same time. Take the two wires (primary
         and secondary) and twist them together. One
         twist in 1.5 cm is ok. Wind the transformer in
         a single layer. Start winding at the half the
         wire! It's better not to use transformer wire
         when you want a good isolation between the
         primary and secondary. Isolated wire wrap wire
         is much better. The best isolation is kynar.
         Wire wrap wire is 0.3 mm and can be used for
         the primary and the secondary. Use different
         colours for primary and secondary!. When you
         wind the transformer with twisted wire wrap
         wire, you can wind only 24 windings in the
         first winding layer. The other 14 winding are
         the second layer. The best way to wind the
         second layer is, to wind 7 windings back on
         each end of the first layer. Otherwise the
         capacitive coupling of both ends of the
         transformer winding are much higher. The isn't
         much space left for the last winding, but
         shouldn't be a problem to wind the 38 windings.
         The number of turns isn't very critical, but
         don't divert more then 2 windings from the
         design. The length of a transformer winding is
         about 75 cm long. When you start with 2 wires
         of 1 meter you have some spare wire length.
         Strip the wires so that you haven't more then 1
         cm slack in the wire after mounting. Remove the
         rest of the wires after soldering the
         transformer in the printed circuit board.

Software

On the software side there has been a lot of changes.
Memory testing routines (for both the EPROM and RAM) are
added to the Leonid monitor. L-memory handling error in
DLIB and DL is now fixed (this caused in some cases
abnormal program execution) and the timeouts are modified
so that these programs can now operate on slower PCs
also.

Where to find the latest stuff?

All the new software and the latest documentation is
available via Internet from ftp.funet.fi, directory
/pub/ham/dsp/alefn/dsp4. They are also available from
jeeves.hut.fi, directory /alefnull.

There is also ongoing mailing list available where the
myriads of DSP CARD 4
technology is discussed:

     DSP4 related list:   dsp4@lists.funet.fi
     Subscribe/unsubscribe with:
          To: mailserver@lists.funet.fi
          Subject: (whatever, you will see it in server's
reply)

          SUBScribe DSP4 Your Personal Name
          UNSUBscribe DSP4

     ("SUBS" is shortest form of the command, longer
version can be used too..
      Commands, and list names are case insensitive.
More info with `HELP'
      command)

     Submission to the list shall be addressed to:
          dsp4@lists.funet.fi

If you don't have possibilities mentioned above, limited
support can be obtained by sending a SASE (and diskettes,
if needed) to the RATS PoBox 88, FIN-02151 ESPOO.