the emu files work just like the subscription files except
you must install a 7742 at u7. they will bring a brain dead
board to life, with no subscription,and have been tested.
hit enter when using loader. DO NOT HIT ANY OTHER KEY.
the hard part is properly installing the emulator,
without screwing any thing up,and getting the u7 file
into the 7742. most eprom burners wont do it. even
if your burner has a 40 pin socket,DO NOT attempt to burn
the 7742 unless it is specified in your owners manual,or
you check with the manufacturer for instructions.
if you cannot do this, i can supply burned 7742s for
$100.
INSTALLING 7742 IN 032 MINIBOARDS
the 7742s dont go in 032s the same as in older boards
you cannot just stick it in a socket and go. even if it
works, it will soon run the bat down.
gi may have used several different pin hookups in this series,
so this is what i would suggest doing.
check to see if all pins of the original u7 are connected
to the circuit board. some may be lifted. then check to see
what pins of the orig u7 have bat power on them. if a pin
is lifted onthe orig, lift the pin on the 7742. DO NOT
APPLY 5VOLTS TO A 7742 PIN UNLESS THERE WAS 5 VOLTS ON THE
ORIG. i have gotten a mini board to work by lifting pins
6,11,17,and 25.
connect a 10k resistor to pin 6. connect a 10k resistor to
pin 11. tie the resistors together.run a wire from the junction
of the 10k resistors to pin 25 and from there to pin 24 of
u4 (this was u5 on the full size boards.) this supplies 5 volts
to the 7742 when board is plugged in,but removes bat power
when unplugged. connect a 200 ohm resistor to pin 17. run
a wire from this resistor to pin 11 of u4. this supplies
colorburst pulses to run the chip instead of the original clock
circuit. the 7742s run very hot. i would suggest removing the
epoxy from the tops of the other chips to aid in cooling,
and not installing the unit in an enclosed area. a small fan
might be a good idea.
(by the way, the chip marked u7 in the mini board is u24 in
full size board. the chip that must be replaced is the
chip at the outer edge of the epoxy ,to the left of the
one marked u7.)
i havent tried this yet, but you might can lift pin 14 to
further reduce bat drain,with no ill effects.
INSTALLING 7742 IN FULL SIZE 032 BOARD
check which pins have bat power,and if any pins are lifted
on orig u7. cut bat power trace to u7.(narrow trace running
along bottom of board, about 4 inches from left side of board
as viewed withe board turned over, and the edge connector facing
up.) lift pins 17 and 25. connect res. and wire as above to
u5 on board.
pin 8 of the orig u7 had bat power, but if you applied power
to it on the 7742, it killed the audio,which would return
when power was removed.
some of this is probably redundant, but it does work.
if you discover a better mouse trap, please let me know.
PS. if you burn your oun 7742, dont worry that the u7 file
has too many bytes in it. just start copying at 0000. it
has the same file in it 4 times,for use with emulator
boards as well as 7742s.
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