UNLOOPER MODIFICATIONS
I have been asked for these items and finally had time to add this page to the site. At the bottom of the page are the links for the Kpyro schematics and other useful items. All of the modifications on this page were based on the Kpyro Design.
Below is the schematic of the adjustable crystal oscillator using an SN7404 standard TTL chip. The trim cap can be anything from 3-50pf. The adjustment range is generally 10-12 Khz. at the unlooper crystal frequency, although it will vary with crystal type. This can be applied to an unlooper or HU Loader. To use this circuit on an existing unlooper or loader, simply remove the crystal from the circuit and take the output from this circuit and apply it to pin 1 of the existing 74xx04 chip.
Below is the schematic diagram for a normal, high quality unlooper powersupply. The 9vdc listed connection is the normal connection to the 47K resistor supplying the LM358 circuit. The output of the LM7805 supplies the rest of the unlooper circuit.
Below is the schematic of the adjustable power supply. It can be used to power the entire unlooper, the way it is, or added to the existing circuit to power the 74HC4053 chips. Be careful of the adjustments as the voltage range of each of these circuits could damage a card if improperly adjusted.
The filtering circuit insures an extremely clean output. The 9 vdc output is used to supply the LM358 circuit. Highly recommended for an HU Loader.
The next circuit is the HU Loader modification to the 74HC4053 circuit to isolate the chips from VCC and supply the new 5 volt source, set to 4.84 vdc to their vcc lines.
The above modification requires you cut all traces to the VCC line connections of both chips and use the new adjustable supply to supply them while the rest of the Unlooper/HUloader uses the normal 7805 chip that is onboard, already.
Next, is the modification to the LM358 circuit to supply the LM317 regulated 8.84vdc to it in place of the original which comes, unregulated, from the plug in the wall transformer. This is recommended for HU loaders. You must cut the trace going to the plug in the wall transformer at pin 8 at the point indicated and connect the new regulated voltage source.
The last modification for use on the HU Loaders is the addition of a 100 ohm pot to the ground connection to the card slot. This is the ground for the card.
The above modification will allow you to make minor voltage corrections to the card. Be very careful of this because if you add too much resistance in the ground leg of the circuit, you can corrupt the read and write. Use just enough to get the glitching going.
Below is the diagram for stacked 74HC4053's for use in an unlooper or loader. This method allows for tighter timing than having the chips seprately mounted.
Below is a basic daughter board schematic. It is used to convert an unlooper into an HU Loader. Layout is not overly critical.
And, for those that have asked, the conversion of the LM358 chip to another op amp. The best one of all, even better than the LM358, is the ua741 chip. The pictorial is below. A note on this modification.... I have received some emails concerning the current threshold of the 741 chip. I have built 5 units using a Motorola ua741 and have experienced no problems with this in circuit. However... as not all chips are the same, there may be some truth to this. To avoid any problems, you may want to replace the 47K resistor in the circuit with one between 12K and 20K. This change should eliminate the problem, if one exists, using this chip. The use of the ua741 chip assumes the regulated 9 volt mod and the isolation of the 74HC4053 5 volt supply.
The alternative to this modification is to
jump pins 1 to 2 (voltage follower configuration) and connecting pin 3 to
pin 4 which grounds the non-inverting input of an LM358. This will require no
chip change and it will get rid of the unbalanced condition of the LM358 chip.
I will add other circuits here from time to time. They will be placed on this page. Each of the circuits, above, has been tested and I have them in current use.
The original Kpyro-Tucker single sided board unlooper schematic.
The original Kpyro unlooper schematic.
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