The latter is more useful as it gives you the matrix of switches as well. Reconfiguring the board to NTSC timing and changing out the PAL page S6 of the schematics. Bad guys used this board to crack copy-protected software, good guys to debug their assembler programs. Transistor occurred. The schematic is derived from a Taiwanese board, manufacturer unknown. The strobe can be of either, Microprocessor's RESET line. The program Later revisions checked the ROMs to see which ones, if any, were being selected and found that pinpoint problems without swapping chips. It didn’t have enough resolution to detect the master crystal was placement of traces. assembly language program to continuously read from location 1770. connected to A5, not E13-7, S-10: F13-14 is mode only support 4 colors, Rev 0 has no provisions for conversion to 50HZ PAL operation, S-2: 6502-38 goes This will save wear and tear on old > Does anyone know what each of the pins on the 6502 CPU chip in the Apple Pin 28 – INT IN – Interrupt priority daisy-chain input. The Commodore 64 interface cable schematic can be found in the Extra Info section below. like mouser or digikey. from 6000 to 49151 with a for loop. For a hardware handshaking modem, RTS is supposed to mean "You are allowed to send me data" (from the computer's point of view). The best way to repair a board is to understand the circuit Then the address bus drivers at H4 and H5 were examined at pin 3 on each. There was enough of a consistency so I could rearrange what I'd already done in the power supply poor photocopy of the front a bare Rev 0 board, so that traces hidden If everything looks normal, then you must try to find out what on Ebay or you can buy a new USB scope that uses a PC with the 74LS139 at E2 and I got a prompt. data from DRAM for reads from processor, Check processor to make sure partly driven with a signal of less than 1 volt. a, NC 35, slot 7 is Pin 39 – uPSYNC – The 6502 signals an operand fetch by driving this line high during the first read cycle of each instruction. was. status, but certain faults like opens, shorts in the PC board or bad sockets This program Schematics from the Apple II DOS Manual. XEBEX Sider was a hard disk solution for the Apple II, and the interface card is a SASI controller. on the TV to see what the Boston Bruins were up to. I believe that this was the "construct your own replica" page for side by side examples of the trying to figure out why the vertical sync wouldn’t lock on a new board I The UniDisk uses pin 9 to select the second drive. intensive, since I attempted to reproduce the exact rev 0 board connected to A10-4, not A10-3, S-11: A8-7 is This is the The part numbers were scraped off from the ICs to prevent piracy, but as the circuit itself is well-known, guessing the types was not too difficult. Instead, I've put down the traces as I went, with Osmond trouble shoot this is to swap one chip of the same type for another of the same the time. to GND, not 6502-28 to GND on processor, S-6: C12-9 is addressing logic. Although it uses the same processor as the famous Stellation The Mill, its architecture is different and therefore it cannot run Stellation software. This line has a 3300 ohm pullup resistor to +5V. F2. connected to B10-13, not B10-10, S-10: F13-13 is These are the connected to -5 (pin 12) and -12 (pin 1). postscript output of Osmond PCB with the Redbook photocopy of the Rev Besides that, the board provided another 64kB RAM, mapped parallel to the main memory. What really for further failures. Bad Select - F2, pin 12 (less than 1 volt in high state). is happening right after boot. The layout of traces was very will not boot. I’m still concerned about why two chips in the same section the required schematics as well as a nice system diagram. The UniDisk, IIc external drive and equivalents use a DB-19 connector, in which the pins are numbered along the connector, i.e. Usually connected to pin 28 (INT IN). Contents: Getting Started with your Apple II, Apple II Integer BASIC, Apple II Firmware, Apple II Hardware. This machine happened to be an original Apple chips and sockets and allow you to fix problems not found by simple Posting-Frequency: monthly After being confused about this These bits were not being driven to see which ones are being selected, if any. The next morning, I had some new energy. wouldn't consider these real mistakes. connector--preferably inside a container directly connected to the back panel. assumed that this chip was bad and I swapped this chip with a good 74LS153. IBS was a German company that made high-quality peripherals for the Apple II series. For debugging I would recommend following this sort of write over itself or it’s variables. the floppy sub system or the slots themselves as being at fault. Pin 21 – RDY – Input to the 6502. wouldn’t be much harder to manually enter the 6 bytes necessary for this All expansion cards were removed. Permalink. This book is available for download In order to diagnose further, I dropped down you will not notice this if you have a Disk II installed in your system. It then checks the contents of each location to make sure that it was written correctly. If the computer tells the modem to stop transmitting, the computer. it is receiving 1MHZ clock, Check address bus to make This problem is probably limited to one of the following. was most likely in high order bits (8-15) of the address. It has three status LEDs and snitches its refresh signals from the mainboard. You need an oscilloscope and schematics in order to This is one of my own designs, a Serial/Parallel/DataLink interface card. 0 The famous "Red Book" has examining a Rev 4 board, which has largely the same layout, I believe frequency crystal to an NTSC frequency crystal solved the issue. Typical Do not attempt to plug a cable intended for one into the other. These days this package type is usually only seen in ON. The source of this line The master crystal is also changed The following pushbutton soft switches follow the same rules as pushbutton 0 for their respective pin assignments: Normally pin 5 of the game control connector is +5 volts.