DKJunior repair Log #1

darthi8nt

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Received DKJunior 2 board set.
Pluged it in and garbage and non booting and no sound yikes.
1. General assesment of the board condition---POOR
2. Corrosion on most of the ICs-- could be because stored in a place with a car battery
3. All sockets will need replaced and all socketed chips will need work as they are missing legs etc... this includes the z80 the D8257 and all eproms and proms.
4. Pulled chips and tested them in winromident here are the results.
 

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Update : Dk Junior garbage on screen 2 board version

CPU Board:
1. Replaced sockets except 5A since it wasn't used.
2. Reburned chips I could salvage but had to use a few new nos chips ordered from Riptor.
Chips reprogrammed were 5B,5C,5E,and 3H all of these tested bad using winromident.
3. Tested all logic chips using a logic probe and logic comparator. Chips tested good.
4. Next focused my attention on the 2114 ram at locations 3A,3B,3C and 4A,4B,4C and wow all tested good using logic probe.
5. USing ESR meter tested all caps on the board but 2 caps gave questionable readings maybe to bad solder. Pulled cap C21 and C37 from the board and tested using ESR meter and tested good low ESR reflowed and double checked and still tested good.
6. Replaced the Z80A chip with new and cleaned the legs on the 8257 chip at location 7E and same for 7H. Tested board and new garbage on screen.
7. Now focus my attention on the Video board.

Video board:
1. Replaced all sockets and did the same as above salvage a few good chips and had to replace some of the bad corroded missing leg ones.
2. Reprogrammed 3N,7C,7D,7E and 7F. Chip 3P tested good in winromident. Wow one eprom was good out of 10 eproms on the board.
3. Checked the caps for volktage and ESR 4 main caps on video board and tested good.
4. checking ic chips using logic comparator showed good. focused my attention on the 2 2114 ram chips.
5. Removed the ram chips and found the corrosion had eaten the pads on a few pins. Mapped out the address lines and resoldered 2 new 2114 ram chips to the board. Using continuity I traced the bad data paths and found this. Using 30 gauge wire wrap refixed the paths from 2R pin8 to 2P pin 8. Now next was 2P pin11 to repair the data path of pin2 of 3P rom. Last was 2P pin14 to repair the data path of pin5 of 3P rom.
6. Plugged both boards back added the rainbow cable back and Wow I was again playing Donkey Kong Junior. Repair fixed. I will add some pictures soon as I'm having trouble finding my camera I took the photos with.
 
here are some pics of repair I finally found my camera.
 

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here are some more
 

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Nice repair!

Feels good to bring a board back from the dead. :D
 
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