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NLG Users Repair Logs and Other Ramblings. Request your very own topic. Just ask any site staff. => Channelmaniac's Arcadecomponents' Old School Repair Logs => Topic started by: channelmaniac on May 04, 2014, 06:45:03 PM
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Subject: Diagnosing RAM errors on Apple IIc/IIe
The Apple IIc and IIe computers have built in diagnostic routines that can be enabled by pressing the Ctrl-Open Apple-Closed Apple-Reset key combination. Depending on the system ROM it will either emit a high pitched squeal followed by a series of high resolution colored screens or will have a series of low resolution colored blocks.
If yours has the series of low res blocks then it will have the newer ROMs which will do the test much faster to completion.
If an error is found there will be a set of 8 zeros and ones. Where there is a 1 it will point to a bad RAM IC on the motherboard.
If there is an asterisk (*) next to the numbers it signifies that the bad RAM is in the 64k to 128k upper memory range on the Apple IIc or on the 80 column card in an Apple IIe.
Run the test again after replacing the bad IC. Do not be surprised to find additional RAM chips that are bad! The test stops as soon as it finds a bad chip so the test will have to be run again and again until it tests with no errors.
If you want to do a continuous memory test to "burn in" the system simply leave the keyboard unhooked from the logic board and it will run continuously.
Enjoy!
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Models: Disk II and 5.25" Uni/Duo Disk drives
Symptom: Drive continuously runs. Any disk inserted gets erased.
This happens if the disk drive cables get hooked up backwards. Replace the 74LS125 IC on the Disk Drive's internal controller board.
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Model: Apple II+/IIe
Symptom: Will not power on
Replaced a 22ohm resistor & a nearby small electrolytic cap in power supply. This is a common problem on the non-Astec model supplies.
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Model: Apple II+/IIe
Symptom: Dead - no power.
Power supply tested good. The +12v line was shorted to ground causing the power supply to shut down. Replaced a shorted monolithic cap on the +12v line to fix.
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Model: IIc/IIc+
Symptom: Floppy disk will not spin or read
Replaced the defective IWM (Integrated Wozniak Machine) IC. This IC controls the floppy disks and is prone to dying if the drives are added or removed with the power on.
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Apple Custom Chip Numbers can be found in a text file in the downloads section of http://www.arcadecomponents.com (http://www.arcadecomponents.com)
These numbers include PALs, HALs, ROMs, PROMs, EPROMs, and custom logic chips.
If you know of any that are missing, please PM me through the board and I'll add them.
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Model: Apple IIgs
Symptom: Dead keyboard & mouse
This actually has two different causes/repairs.
The first is to open up the keyboard and repair cracked solder joints on the ADB (Apple Desktop Bus) ports.
If that's not it the second is to replace the 8 pin square black plastic filter network on the IIgs logic board. It is situated next to the ADB port on the back corner of the motherboard. It has 4 toroid core filters built into it. If one of the 4 filters has no continuity then the ADB port will be dead.
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Model: Apple II+/IIe Power Supply
Symptom: Dead.
This was the Astec version of the Apple II Power Supply.
Replaced a blown 2.75A metric size fuse and a shorted bridge rectifier. Bridge rectifier can be replaced with an NTE5319 but it will require the holes in the board to be enlarged to accomodate the larger legs of the replacement device. This replacement device has a higher current rating and should last longer than the original part.
Replaced C7, a 10v 220uf 85 deg C capacitor with a 16v 220uf 105 deg C capacitor. This cap is a common failure item and should be replaced in any Astec version Apple II+/IIe power supply.
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Model: IIe motherboard
Symptom: Dead. Garbage on screen.
Checked the activity on the DRAM legs with a logic probe and found they were pulsing in slow sync which was an odd pattern. Replaced the 6502 CPU and ran diagnostics on the board.
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Model: Apple II+/IIe power supply
Symptoms: Makes funny noises. Does not work.
Power supply was not an original Apple supply but rather a clone. Found 3 burst capacitors and 4 leaking capacitors in the output section. Replaced the bad caps and tested the rectifiers for shorts. None were found shorted. Reassembled and tested the power supply.
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Model: Apple II+
Symptom: Dead, Screen full of @, #, and $ symbols
Removed a 64K DRAM chip that was plugged into the DRAM socket the language card normally plugs into. This is an incorrect chip (5v only... The 16K chips are +5/-5/+12v) and was getting red hot. Replaced every 4116k DRAM as they were all blown - 23 dead DRAMs (the 24th chip being the incorrect 64k chip). Replaced a bad 74S86 at location B2.
The system would then try to boot but would fail. The address lines on the DRAMs were incorrect. Two were dead, 1 was stuck high, and 1 was racing. Replaced bad 74LS153 chips at E11, E12, and E13 to fix. Now the system would boot but drop down to the Monitor ROM. Replaced the D8 and F0 ROMs and burned in the board for several hours.
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Model: //c
Symptom: Dead. Blocks on screen.
Replaced bad 65C02 CPU, ran the built-in tests, and tested the floppy drive.
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Model: //e
Symptom: Dead
Board had physical damage to the CPU socket and 1 resistor pack.
Replaced missing CPU, CPU socket, broken resistor pack, and the socket on the 74LS10 IC. Replaced defective HAL chip. Tested.
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Model: Apple IIgs
Symptom: Dead
Replaced bad 470uf @ 16v, 2x 1uf @ 50v, and a 10uf @ 25v cap that had high ESR and replaced an open 100K ohm 1/2w resistor in the power supply. Ran built-in diagnostics and tested the floppy drive port.
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Model: Apple II+
Symptom: Random crashes
Reseated bank 1 RAM (tarnished legs), reseated multiple chips that were raised up in their sockets, tested the ROMs and D8 was bad. Board would boot but would not recognize all of its RAM. Replaced bad RAM at D10, and reseated the 74LS194 at B4 as pin 8 (ground) was outside its socket. Ran memory tests and Apple DOS 3.3.
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Model: Apple II+
Symptom: Dead. Garbage on screen
Replaced 4 bad RAMs in bank 1 at C4, C7, C8, and C9. Replaced bad 74LS11 at B12 that had a weak output. Replaced 2n3904 transistor and ran RAM tests. Replaced bad RAM in bank 3 at E10.
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Notes: Apple II+ memory test:
Open the monitor by typing: CALL -151<ENTER>
Type in the following (with a space at the end before hitting <ENTER>!!!):
C050 C053 C054 C057 N 265:FF N 266<265.BFFEM 266<265.BFFEV 265:0 N 266<265.BFFEM 266<265.BFFEV 34:14 <ENTER>
The screen will show graphics at the top with text at the bottom and will alternate between a black screen with ? for the bottom four rows and a white screen with inverse @ symbols for the bottom four rows.
Watch the screen carefully! If it finds an error, it will flash the text on the screen just before it switches to the next test. The error will look like this for example: 8000 (FF) 7F where the 8000 is the address, FF is the data written, and 7F the data read.
Addresses: 0000-3FFF = Bank 1 (chips C3 - C10) = 0 to 16k
Addresses: 4000-7FFF = Bank 2 (chips D3 - D10) = 16 to 32k
Addresses: 8000-BFFF = Bank 3 (chips E3 - E10) = 32 to 48k
Data lines start on the left. 7F in the example is 01111111 in binary. The 0 is the bad bit in this example and is the upper most data bit. Reading from left to right, the upper most bit would be the chip at position E10
Enjoy!
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Model: Apple II+
Symptom: CTRL key not working
Replaced bent pin 23 on the keyboard to controller board connector and tested.
Note: Pin 1 on the socket is unused and is a spare pin that can be taken to replace a bent one.
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Model: Apple IIe
Symptom: "-" key not working
Keyboard had physical damage. Replaced bad key switch and missing key cap. Tested
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Model: Apple 3.5" drive
Symptom: Intermittent read errors
Cleaned and lubricated drive. Tested
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Model: Rana Systems Elite One floppy drive
Symptom: Random read errors
Cleaned and lubricated drive. Tested.
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Model: Apple 3.5" disk
Symptom: Would not eject
Cleaned and lubricated drive mechanism. The grease had turned sticky and was causing the drive eject motor to bind and stop.
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Model: //e 80 Column / 64k Memory Expansion card
Symptom: Bad RAM
Fails self test with an error of *1 0 0 0 0 0 0 0
Replaced bad RAM at location 8 and tested
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Model: Disk II interface card
Symptom: Missing chip
Replaced missing 74LS05 IC and tested
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Model: Jameco 16K Language Card (For Apple II+)
Symptom: Crashes computer when installed
Replaced a bad 74LS09 and a bad 74LS175 IC chip. Tested.
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Model: Apple IIc
Symptom: Dead, flashing garbage on screen. All the RAM chips get very hot.
Board had a short across 2 of the large tinned contact areas on the front left corner of the board. This shorted approx 17vDC across to the +5v bus.
Replaced all 16 RAM chips and tested
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Model: ZIP GSX accelerator for IIgs
Symptom: Will not boot.
Unit had damaged components and attempted repairs.
Removed the old 70ns cache RAM and the .600" sockets and cleaned up the board. Installed .300" sockets and replacement 25ns cache RAM. Removed the 2 burn damaged DIP switches and installed new ones. Removed cut pins from the board and installed replacement tantalum capacitors. Removed hacked on crystal oscillator, installed a new oscillator socket and patched damaged traces. Tested board with a 28, 32, and 33.333MHz oscillator successfully.
CPU on the board was too slow to work with a 40MHz oscillator in accelerated mode. Now that the faster RAM is installed, customer is ordering a higher speed rated CPU to test further overclocking of the accelerator.
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Model: Bell & Howell II+
Symptom: Dead. Garbage on screen.
RAMs tested good in a NeoLoch Inquisitor. CPU tested good in a test jig. ROMs tested good in another II+ main logic board. The 74LS153, LS174, and LS257 chips that control the inputs, outputs, and data line multiplexing tested good. Found a 74LS157 with a dead output on pin 7 at location C12. Replaced it and tested the computer.
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Model: Apple IIc w/memory expansion
Symptom: Dead. Graphical checkerboard on screen
Replaced dead 65C02 CPU. Reinstalled memory expansion board and tested - failed RAM. Replaced bad 74LS173 with a rotted pin on the memory expansion board and tested again, successfully.
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Model: Apple II+
Symptom: Dead, garbage on screen, missing a chip
Replaced missing 9334 and its socket. Tested.
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Model: Apple II+
Symptom: Dead, missing IC
Another one with a missing 9334 chip and bad socket. Installed a new IC and socket and tested.
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Model: Apple II+
Symptom: Dead
Replaced missing 9334 chip and its bad socket. Replaced bad 6502 CPU and tested.
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Model: Apple II+
Symptom: Dead, no power
Replaced bad fuse and bridge rectifier in the power supply. One of the HV side capacitors failed during testing. Replaced all 4 high voltage side capacitors and tested.
The bridge rectifier was not fully shorted, but instead had a leaky diode. This damaged the capacitor and caused it to fail during testing.
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Model: Apple II+
Symptom: Will not boot. Sometimes boots to software monitor prompt
Used a donor leg from another IC to fix a broken pin on one ROM. Fixed 2 bent under pins on 2 ROMs and tested. Replaced one bad RAM chip in Bank 0 and retested successfully. Installed the customer's 16K RAM card and successfully booted DOS and loaded Integer Basic onto the card.
Made and installed a replacement keyboard cable.
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Model: Apple IIe
Symptom: Dead
Replaced one exploded main filter cap and the 220uf @ 10v cap next to the main switching transistor. Replaced blown fuse, removed the RIFA cap, and tested.
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Model: //e Platinum
Symptom: water damage
Swapped the customs, ROMs, and CPU over to a replacement parts motherboard. Tested. Replaced 5 keys on the keyboard and tested. Replaced bad speaker and retested.
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Model: //e Platinum
Symptom: Dead
Replaced 2 1uf@35v and 1 10uf@35v capacitor in the power supply. The 2 1uf caps had leaked and electrolyte was cleaned up. Tested. Replaced bad F key and Caps Lock key. Retested.
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Model: //c
Symptom: Dead. No video output.
Replaced bad video jack and tested. Dead with garbage on screen. Upgraded from ROM FF to ROM 03 and tested. RAM Error ZP 10000000. Replaced RAM chip and tested.
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Model: Apple IIe
Symptom: Smoked
Opened the power supply and removed the fried RIFA cap. Cleaned the leakage and smoke damage out of the power supply then recapped it. Tested.
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Model: Apple IIe Astec power supply
Symptom: dead
Replaced shorted Q2 (bottlecap transistor), shorted SCR, and a smoked R17. Recapped the power supply and tested. Power supply made a loud repeating CRACK CRACK CRACK sound. Found a broken wire on the bottom of the leg on part of T3 that connected to the base of Q1. Reattached the wire to the top of the leg and tested successfully.
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Model: Apple IIe
Symptom: Cannot connect printer
Card was missing the connector dongle. Built a replacement dongle, attached printer, and tested.