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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 December 18, 2014, 10:14:51 PM
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Model: Raspberry Pi
Symptom: Dead
Replaced broken L5 coil on the bottom of the board and tested.
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Model: Raspberry Pi
Symptom: Parts, smashed unit.
Board had bad physical damage. Replaced Leaking C6, broken connector S2, broken video jack at S4, bent USB port at S8, and bent Ethernet port at S7. Replaced bent DIP header at P1 and tested.
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Model: Sharp X68000 Super w/Xcellent 30S
Symptom: CPU burns fingers. System will not boot with 68030 installed
Replaced dead 68030 CPU and tested.
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Model: Atari 800
Symptom: Dead keyboard
Keyboard lines looked good with a logic probe but the computer wouldn't recognized any key presses. Resoldered the power headers on the power supply board and main board to fix cracked solder issues then replaced a defective 6520A PIA chip. Tested.
Supplied Galaxian cartridge would not work. Cleaned edge connector and successfully played the game.
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Model: SuperMicro Dual Xeon computer
Symptom: Won't power on
Computer would just beep and immediately shut off the power. Removed the heatsinks/fans from both CPUs and reseated them in their PGA sockets. Reinstalled the CPUs and powered up the computer successfully but had no video. Replaced bad video card and retested successfully.
The Intel PGA style Xeon CPUs have problems with the CPUs becoming disengaged from their sockets when the systems are shipped and/or dropped. This computer traveled 1700 miles in a bouncing trailer. :)
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Model: OSEPP FTDI RS-232 Interface for Arduino
Symptom: Dead. Connector was pulled from the board
Cleaned the SMT pads on the board and the connector then resoldered the connector to the board. Tested.
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Model: Inland FT232 FTDI RS232 Interface for Arduino
Symptom: Dead. Smoked
Replaced an open surface mount coil on the USB 5v line and tested.
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Model: Dell XPS 700
Symptom: Dead
Replaced 8 popped electrolytic capacitors on the main logic board and tested.
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Model: Gateway T3124
Symptom: HDD errors in PST file
Opened the case on the shop email/EPROM burning PC (Windows XP!) to replace the hard drive and discovered multiple bad caps. Replaced 5 1500uf @ 10v and 3 1500uf @ 6.3v capacitors, replaced the hard drive with an SSD, and migrated the data. Rebuilt the Outlook PST file to fix errors and disabled the Windows Updates service to fix a CPU spiking issue.
Downloaded months of emails to wade through.
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Model: PCjr 128K Memory Expansion
Symptom: Modify it to 512K memory
Desoldered 16 4164 DRAM chips, installed 16 sockets, and inserted 16 41256-12 DRAMs. Desoldered the pads for memory expansion jumpers, cut a trace between 2 of the pads, installed the headers and the jumper for 512K. Tested.
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Model: Sharp X68000
Symptom: Poor sync signal
Replaced bad 74ALS05 IC in the sync output circuit and tested.
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Model: Macintosh SE/30
Symptom: 4 broken SIMM sockets.
Replaced broken SIMM sockets and gave board back to local owner for testing.
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Model: Intel SDK-86
Symptom: Dead, garbage on LEDs
Replaced several missing jumpers and tested. Display shows -Err. Repaired stuck ':' key on key pad and performed the system Checkout Procedure listed in the assembly manual.
NOTE: If W36 - W38 jumpers are not installed, CPU will not boot. If W40/W41 jumper is not installed, CPU will not have its clock.
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Model: Intel SDK-86
Symptom: 'Err' on display
Repaired stuck ',' key on key pad and performed the system Checkout Procedure listed in the assembly manual.
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NOTE: Intel SDK-80 Keyboard Troubleshooting
When the display shows -Err there is a stuck key. To find the key you can try to turn the unit upside down and use a multimeter on continuity test mode to find the switch.
Sometimes the switch will only show stuck when the board is right side up. When this happens, use a logic probe on pins 38, 39, 1, 2, 5, 6, 7, and 8 of the Display/Keypad controller IC. These pins should read high when no keys are pressed. When you find one that is flipping logic states then you narrowed down the stuck keys to three possibilities. If your logic probe has audio beeps then press each of the three keys while listening. There will be a subtle change in audio for good keys and no change when you press the stuck key.
The keys can be desoldered and carefully disassembled. There is a brass piece inside that can be very gently lifted up about 1/16" and they key reassembled. Test the key out of circuit then before it's reinstalled, power up the computer and if there are no more stuck keys you'll be at the standard prompt "- 86 1.1". Resolder the key switch back in circuit and follow the Checkout Procedure listed in the assembly manual to test all the keys and the display elements.
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Model: Commodore PET 2001
Symptom: Dead, garbage on screen
Replaced 2 bad video RAMs with an adapter and a 6116 SRAM chip to fix the video issues. Used a Fluke 9010A with the 6502 pod to test the system. Replaced a bad 74LS04 driving the address lines to the RAM to fix RAM DCD (decoding) errors found by the Fluke system. System would intermittently boot but with no cursor. Replaced a bad 74154 to fix RAM read errors when the 2nd bank of 4K RAM was added. The RAM tests would then fail again with RAM DCD errors on the Fluke. Reinserted the 6520 for the keyboard in the proper direction - it was in backwards. This returned the cursor and keyboard function when the system would boot and resolved the RAM DCD errors on the Fluke.
Replaced the CPU socket and a bad CPU to fix the boot problem. Installed the replacement RAM/ROM module and used the self test function on it to test the system. Removed the OEM ROM and RAM chips and set the replacement module to boot BASIC 4.0 and use its 32K SRAM chip. Tested again then reassembled the system.
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Model: SDS Z80 Starter Kit single board computer
Symptom: Dead. Filthy. Some jammed keys.
Took it apart, removed all the dirt crusted sockets, cleaned the board, installed new sockets, then put it back together. Took 3 of the key banks (4 each) apart and fixed the jammed keys.
Replaced 1 21L02 RAM that failed out of circuit testing. Replaced another 21L02 that read 3.3K to the +5v line on A3 when all the others read 9.9K (10K pull up resistors were in the circuit.) Powered it up and it's still dead.
Started digging through the circuitry and noticed it would die when toggling the display / keyboard circuit. Another bank of keys that felt OK were actually shorted on 2 keys. Like my SDS-86 single board computer, this won't boot if keys are pressed. Disassembled this shorted key switch bank and fixed the bent wires inside the switches. Reassembled, disassembled and redid the wires again, then put it back together successfully.
Powered it on and was greeted with the '-' prompt
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Model: Timex Sinclair 1500
Symptom: No response from keyboard
Keyboard had a cracked mylar film, typical of these. Procured a replacement then installed and tested it successfully.
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Model: DTK XT Clone
Symptom: Missing BIOS chip
Replaced missing BIOS chip and installed a jumper on the key lock pins to let keyboard work. Tested.
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Model: DTK 'PIM-Turbo' XT Clone
Symptom: Will not boot
Replaced shorted Tantalum cap on the +12v line after it popped. Replaced corroded slot connector. Board would pass all diagnostics using the test BIOS until the CGA RAM test when it would fail and lock up. Inspected board and found a gouged trace on the bottom. Patched the trace with a short piece of Kynar wire and replaced a popped Tantalum cap on the -12v line. Board now passes all tests and boots.
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Model: Turbo-XT 8MHz Motherboard
Symptom: Dead
Replaced shorted tantalum cap holding the power supply in shutdown. Tested.
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Model: Wyse 60 Terminal
Symptom: Dead.
Terminal had previous attempted repairs done to it and had 2 diodes half desoldered.
Replaced shorted diode D203, a high speed 1000PIV diode, and the replacement became red hot and shorted. Replaced 2 caps in the horizontal section with cracked tops. Measured the high voltage at the CRT and it was only 5KV. Replaced the flyback and D203 again and tested.
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Model: DEC 486 PC
Symptom: Dead
Fails boot. CPU was not sitting flat in socket. Pulled chip and straightened 2 terribly bent pins and 1 slightly bent pin. Reinserted CPU into PGA socket and tested.
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Model: Osborne 1
Symptom: Dead
Replaced two bulging capacitors on the power supply board. Replaced one shorted tantalum capacitor on the main logic board. Booted computer. B: drive errors. Lubed the worm gear and spindle clamp bearing on the B: drive then moved a shaft hold down that was interfering with the head moving back to Track 0. Tested. Took unit to Dallas Makerspace where a member replaced the brittle leather handle with a custom made one. Cleaned exterior of unit and retested.
This unit was being entered into the fundraising auction at VCF Southwest.