Board from member capnswab
Symptoms: Non Booting
I must say this was one of the cleanest newest looking best kept DK boardset I have seen.
Ok! so here we go again another DK wont do anything. Before I start I always use a brand new Z80A so I can almost rule it out unless the socket is bad.
1. first checked caps and all caps except 2 were great the 2 caps on CPU board 470uf 16v both had been clipped off at the leads and resoldered back to the leads instead of desoldering cap from the actual pcb. Replaced. Tested game still not boot.
2. Tested all the transistors and diodes 3 transistors failed Q4 and Q14 tested bad on CPU board and so did Q1 under metal shield on Video board. Solution replaced all transistors. Note all the diodes tested good but a few like Is953 had to have a leg removed out of circuit to test good. Result all diodes were good. plugged game back in and still blank screen.
3. Started pushing down on chips and all of a sudden game booted.Hmmmm even played a game. Turned off and turned back on to a black screen. Using my finger put resistance on 2 diodes in sound section and could hear my local mexican radio station. Try it its fun. Place finger across D6 and D7 and you will get a radio station coming from your speakers.Next I used my logic probe to short a couple pins of 3h on cpu board to hear that Sounds of the game were working. Started pushing again and game booted. Was about to get out my logic comparator when game sounds were loud so I moved the game board acidentally by trying to turn down the audio pot and game went dark again and no sound.
4. Replaced the audio pot with a new one pot only ohmed out to 8.5 ohm and should be around 10. turned game on and nothing. Now I was again getting ready to start the tedious process of chip failure but first lets check voltages so I started with the video side. So I know from working on these boards wrong power below 4.9 won't boot and I was getting a failure in volts across the board but the Cpu side was good.
5. Video board attention I started looking at 10116 and 10136 because i know if these chips fail the board won't boot they were reading like 4.6 volt hmmm something before them is wrong back to the section of the heat shield which I still had off the board. Tested the ceramic caps they were good which got me thinking maybe the crystal isn't working and is faulty so a trick I used before I placed my ohm meter to 200vdc and put the black lead to GND and the red lead went to the crystal leg an as soon as I touched it the game came up with pic and sound as repeated this procedure a couple of times with same results. Solution replaced both crystals on CPU and Video board with new and now the game started like a champ could move it flip it upside down push on it and it still worked perfect. Turned game off and back on and game booted perfect. Played like this for a few hours and let game run for awhile even played to level 5 before dying.
Another DK brought back from the dead.
Symptoms: Non Booting
I must say this was one of the cleanest newest looking best kept DK boardset I have seen.
Ok! so here we go again another DK wont do anything. Before I start I always use a brand new Z80A so I can almost rule it out unless the socket is bad.
1. first checked caps and all caps except 2 were great the 2 caps on CPU board 470uf 16v both had been clipped off at the leads and resoldered back to the leads instead of desoldering cap from the actual pcb. Replaced. Tested game still not boot.
2. Tested all the transistors and diodes 3 transistors failed Q4 and Q14 tested bad on CPU board and so did Q1 under metal shield on Video board. Solution replaced all transistors. Note all the diodes tested good but a few like Is953 had to have a leg removed out of circuit to test good. Result all diodes were good. plugged game back in and still blank screen.
3. Started pushing down on chips and all of a sudden game booted.Hmmmm even played a game. Turned off and turned back on to a black screen. Using my finger put resistance on 2 diodes in sound section and could hear my local mexican radio station. Try it its fun. Place finger across D6 and D7 and you will get a radio station coming from your speakers.Next I used my logic probe to short a couple pins of 3h on cpu board to hear that Sounds of the game were working. Started pushing again and game booted. Was about to get out my logic comparator when game sounds were loud so I moved the game board acidentally by trying to turn down the audio pot and game went dark again and no sound.
4. Replaced the audio pot with a new one pot only ohmed out to 8.5 ohm and should be around 10. turned game on and nothing. Now I was again getting ready to start the tedious process of chip failure but first lets check voltages so I started with the video side. So I know from working on these boards wrong power below 4.9 won't boot and I was getting a failure in volts across the board but the Cpu side was good.
5. Video board attention I started looking at 10116 and 10136 because i know if these chips fail the board won't boot they were reading like 4.6 volt hmmm something before them is wrong back to the section of the heat shield which I still had off the board. Tested the ceramic caps they were good which got me thinking maybe the crystal isn't working and is faulty so a trick I used before I placed my ohm meter to 200vdc and put the black lead to GND and the red lead went to the crystal leg an as soon as I touched it the game came up with pic and sound as repeated this procedure a couple of times with same results. Solution replaced both crystals on CPU and Video board with new and now the game started like a champ could move it flip it upside down push on it and it still worked perfect. Turned game off and back on and game booted perfect. Played like this for a few hours and let game run for awhile even played to level 5 before dying.
Another DK brought back from the dead.
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