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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 July 08, 2017, 09:04:05 PM
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Model: Nibbler (Vanguard conversion)
Symptom: Dead
Board had attempted repairs done.
All 2732 EPROMs were replaced in an attempted repair but were programmed using a USB EPROM programmer that couldn't source the 25V properly. All the EPROMs had weak bits and failed checksums when read multiple times.
Reprogrammed all of the EPROMs, replaced the 2 74LS244 ICs on the data lines, replaced a bad CPU socket, replaced a previously replaced single wipe ROM socket and patched 2 damaged traces. Board would then boot but had no sync. Removed a sync hack and restored the sync circuit and had partial sync with low output levels. Replaced the 74LS05 ICs in the sync output and reduced the value of R22 from 1K to 470 ohm to fix the low sync output issues. Tested.
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Model: Warp Warp
Symptom: Dead
Board had been partially converted to DC and came with a JAMMA adapter. Removed 4 additional diodes and cut a ground trace to use as -5v DC then ran a -5v wire on the supplied JAMMA adapter. Jumpered the 12 and -5v DC to the output of the regulators on board and the +12 to the audio amp chip. Jumpered the +5v from the diode solder pads to the +5 rail. Replaced 2 corroded RAM sockets and 2 corroded ROM sockets. Cleaned the pins on 2 RAMs and replaced ROMs at 1P and 1T that had multiple rotted legs. Tested to find video would not sync. Added in a ground wire to the video ground pin on the supplied JAMMA adapter and tested successfully.