blog:386_shootout_forex

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blog:386_shootout_forex [2021/03/09 16:44] – [Keyboard Socket Removal & Replacement] johnblog:386_shootout_forex [2021/04/20 10:16] (current) – [Initial Testing] john
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 ==== Detailed Problem Images ==== ==== Detailed Problem Images ====
 +
 +I took these images after the board had arrived:
  
 {{:blog:386:img_1900.jpg?300|}} {{:blog:386:img_1901.jpg?300|}} {{:blog:386:img_1902.jpg?300|}} {{:blog:386:img_1903.jpg?300|}} {{:blog:386:img_1900.jpg?300|}} {{:blog:386:img_1901.jpg?300|}} {{:blog:386:img_1902.jpg?300|}} {{:blog:386:img_1903.jpg?300|}}
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 These UMB regions can then be used to load drivers and TSR's high, using the //highdvr// and //hightsr// utility included with The Last Byte memory manager similar to the MS-DOS commands //devicehigh// and //loadhigh//. These UMB regions can then be used to load drivers and TSR's high, using the //highdvr// and //hightsr// utility included with The Last Byte memory manager similar to the MS-DOS commands //devicehigh// and //loadhigh//.
  
 +=== BIOS ===
 +
 +BIOS from my motherboard:
 +
 +   * {{ :blog:386:forex_386_486.zip |}}
 ===== Repairs ===== ===== Repairs =====
  
 ==== Keyboard Socket Removal & Replacement ==== ==== Keyboard Socket Removal & Replacement ====
  
-{{:blog:386:img_1901.jpg?500|}} {{:blog:386:img20210309164034.jpg?400|}} {{:blog:386:img20210309164039.jpg?400|}} +Before removal:
-==== 74LS245N Removal & Replacement ====+
  
 +{{:blog:386:img_1901.jpg?500|}} 
 +
 +Keyboard port and battery header removed:
 +
 +{{:blog:386:img20210309164034.jpg?500|}} {{:blog:386:img20210309164039.jpg?500|}}
 +
 +Damaged traces cleaned with fibreglass pencil, neautralised with white vinegar and then thoroughly cleaned with isopropyl alchohol:
 +
 +{{:blog:386:img20210309201629.jpg?600|}}
 +
 +Fingers crossed that there isn't any more damage - there doesn't appear to be, so this looks like it has been caught in time. The battery header uses a diode as standard (part D4, just to the right of the header solder pads), so no chance of a battery pack getting charged and going bang. A standard 4-pin (+, N/C, N/C, Gnd) external pack will work fine.
 ==== ISA Socket Removal & Replacement ==== ==== ISA Socket Removal & Replacement ====
  
 +{{:blog:386:img20210309215725.jpg?500|}} {{:blog:386:img20210309215953.jpg?500|}} 
 +
 +{{:blog:386:img20210309220007.jpg?500|}} {{:blog:386:img20210309220035.jpg?500|}}
 +
 +Unfortunately a trace under the 74LS chip was damaged on removal of that chip - on removal of the ISA socket it looks to connect pin 3 of the 74LS245N with pin 2 of the ISA sockets either side of it. This will need to be repaired with a short section of kynar wire to bridge those three pins:
 +
 +{{:blog:386:img20210309213520.jpg?200|}}
 +
 +New 74LS245N DIP socket and 16bit ISA socket in position:
 +
 +{{:blog:386:img20210309222634.jpg?500|}} {{:blog:386:img20210309222717.jpg?500|}}
 +
 +74LS245N pin3 and ISA socket pin2 link wire in place:
 +
 +{{:blog:386:img20210310205822.jpg?400|}}
 +{{:blog:386:img20210310205908.jpg?400|}}
 +{{:blog:386:img20210310210556.jpg?400|}}
 +{{:blog:386:img20210310211603.jpg?400|}}
 +
 +{{:blog:386:img20210310211616.jpg?400|}}
 +{{:blog:386:img20210310213144.jpg?400|}}
 +{{:blog:386:img20210310215421.jpg?400|}}
 ==== ISA Socket Cleaning ==== ==== ISA Socket Cleaning ====
 +
 +Scrubbed with white vinegar on a toothbrush, then thoroughly cleaned with isopropyl alchohol:
 +
 +{{:blog:386:img20210309201643.jpg?500|}} {{:blog:386:img20210309201648.jpg?500|}} 
 +
 +{{:blog:386:img20210309201702.jpg?500|}}
 +
 +I'm pleased with these - other than the one with the missing pin, they've all come up really rather nice; hopefully just the one will need replacing now.
 +
 +===== Initial Testing =====
 +
 +Sadly, initial testing after reassembling the board after replacing the obvious components results in //no video// and //no error code beeps//. Processor and other chips were cold and didn't heat up, indicating no clock signal.
 +
 +First thing was to check all of the jumpers on the board, and many of them had been either removed or set to something //other// than what they were supposed to be for a 386DX-40. With those set correctly, and the programmable clock generator set to 40MHz the processor and other supporting chips now get warm, but still no output on screen or via the speaker.
 +
 +Next test is probably check with a POST diagnostic card and perhaps check some other clock signals.
 +
 +**[Update - 12/03/2021]** //POST diagnostic card arrived.//
 +
 +After initially having to repair two broken LED's on the __new__ diagnostic card, I eventually got it working and up and running in the Forex board. It confirmed that all voltages were present, and that the system reset behaviour was working, but no error codes are present:
 +
 +{{:blog:386:img20210312210910.jpg?500|}}
 +
 +Not sure how to proceed from here.....
 ===== Configuration ===== ===== Configuration =====
  
  • blog/386_shootout_forex.1615308243.txt.gz
  • Last modified: 2021/03/09 16:44
  • by john