This thread is continuing from here:
http://forums.arcade-museum.com/showthread.php?t=237821
and here:
http://forums.arcade-museum.com/showthread.php?t=249208
--------------
This is my OMG I can't believe I'm doing this blog along with an appeal for advice because this is the first time I've tried anything more complicated than recapping a monitor.
At the end of the day hopefully I'll have learned something, fixed this monitor, and people that come after me reading this thread will have something useful.
I lost deflection on the bottom half of my G08 on my Star Trek. Before that the image was *okay* but had issues with the graphics being jittery.
So I pulled the monitor and started by checking to see which of Mongo's G08 mods had been done to it. The voltages going in had been modded for 120v operation or 45v AC to the monitor -- just what it should be. Check! And the deflection transistors were mounted inside the heat sink rather than the default outside. Check! The power supply had been supplemented with a switching power supply to handle the +5. Check!
So all of Mongo's recommended G08 mods were complete.
So per Kstillin's advice, I swapped the connectors for the deflection transistors and fired the game back up. Surprisingly, I had deflection although I didn't exhaustively test it. When I flipped the connectors back to normal I went back to intermittently having deflection on the bottom half of my screen.
So my current advice was to start by re-pinning those connectors to the deflection transistors. Fortunately they look like standard .156 connectors and I have some .156 pins on hand. I don't have any 7 pin connector shells on hand so my plan is to remove each wire/pin, cut it, re-pin it, and re-use the same shell. Hopefully that'll be a better, more robust solution than what I have now and it certainly isn't going to hurt.
Before I started doing this I decided to test the deflection transistors with my DMM. The G08 FAQ has a nifty section on testing these involving testing each transistor in 6 different ways through their wiring harness so you don't have to even pull them to test them.
Here's what I did. I started with these instructions (formatted better for posting here). These transistors are NPN.
[FONT=Arial, Helvetica, sans-serif][SIZE=-1]1) Set your meter to the diode test. Connect the red meter lead to the base of the transistor. Connect the black meter lead to the emitter. A good NPN transistor will read a JUNCTION DROP voltage of between 0.45v and 0.9v. A good PNP transistor will read OPEN.
2) Leave the red meter lead on the base and move the black lead to the collector. The reading should be the same as the previous test.
3) Reverse the meter leads in your hands and repeat the test. (EDIT: Does the text just before this go with #2? Wasn't sure what to do with this so did nothing). This time, connect the black meter lead to the base of the transistor. Connect the red meter lead to the emitter. A good PNP transistor will read a JUNCTION DROP voltage of between 0.45v and 0.9v. A good NPN transistor will read OPEN.
4) Leave the black meter lead on the base and move the red lead to the collector. The reading should be the same as the previous test.
5) Place one meter lead on the collector, the other on the emitter. The meter should read OPEN.
6) Reverse your meter leads. The meter should read OPEN. This is the same for both NPN and PNP transistors. Thanks to Randy Fromm <[email protected]> for this excellent summary of the diode test method.
And here are my results with my DMM set to diode test where a green cell is a passed test and a red cell is a failed test:
[/SIZE][/FONT][FONT=Arial, Helvetica, sans-serif][SIZE=-1]
[/SIZE][/FONT][SIZE=-1]So according to my testing one of the 4 transistors is good, two are train wrecks, and one is marginal.
I tried double checking some of these tests with my other el-cheapo DMM and it came up with different numbers that were higher but basically only changed one lower failing score to a pass on DT1.
Comments? Can I basically mostly have deflection with numbers like these? Or is it a "there's no way you could have deflection with numbers like that" and there's something wrong with my testing or DMM?
[/SIZE]
http://forums.arcade-museum.com/showthread.php?t=237821
and here:
http://forums.arcade-museum.com/showthread.php?t=249208
--------------
This is my OMG I can't believe I'm doing this blog along with an appeal for advice because this is the first time I've tried anything more complicated than recapping a monitor.
At the end of the day hopefully I'll have learned something, fixed this monitor, and people that come after me reading this thread will have something useful.
I lost deflection on the bottom half of my G08 on my Star Trek. Before that the image was *okay* but had issues with the graphics being jittery.
So I pulled the monitor and started by checking to see which of Mongo's G08 mods had been done to it. The voltages going in had been modded for 120v operation or 45v AC to the monitor -- just what it should be. Check! And the deflection transistors were mounted inside the heat sink rather than the default outside. Check! The power supply had been supplemented with a switching power supply to handle the +5. Check!
So all of Mongo's recommended G08 mods were complete.
So per Kstillin's advice, I swapped the connectors for the deflection transistors and fired the game back up. Surprisingly, I had deflection although I didn't exhaustively test it. When I flipped the connectors back to normal I went back to intermittently having deflection on the bottom half of my screen.
So my current advice was to start by re-pinning those connectors to the deflection transistors. Fortunately they look like standard .156 connectors and I have some .156 pins on hand. I don't have any 7 pin connector shells on hand so my plan is to remove each wire/pin, cut it, re-pin it, and re-use the same shell. Hopefully that'll be a better, more robust solution than what I have now and it certainly isn't going to hurt.
Before I started doing this I decided to test the deflection transistors with my DMM. The G08 FAQ has a nifty section on testing these involving testing each transistor in 6 different ways through their wiring harness so you don't have to even pull them to test them.
Here's what I did. I started with these instructions (formatted better for posting here). These transistors are NPN.
[FONT=Arial, Helvetica, sans-serif][SIZE=-1]1) Set your meter to the diode test. Connect the red meter lead to the base of the transistor. Connect the black meter lead to the emitter. A good NPN transistor will read a JUNCTION DROP voltage of between 0.45v and 0.9v. A good PNP transistor will read OPEN.
2) Leave the red meter lead on the base and move the black lead to the collector. The reading should be the same as the previous test.
3) Reverse the meter leads in your hands and repeat the test. (EDIT: Does the text just before this go with #2? Wasn't sure what to do with this so did nothing). This time, connect the black meter lead to the base of the transistor. Connect the red meter lead to the emitter. A good PNP transistor will read a JUNCTION DROP voltage of between 0.45v and 0.9v. A good NPN transistor will read OPEN.
4) Leave the black meter lead on the base and move the red lead to the collector. The reading should be the same as the previous test.
5) Place one meter lead on the collector, the other on the emitter. The meter should read OPEN.
6) Reverse your meter leads. The meter should read OPEN. This is the same for both NPN and PNP transistors. Thanks to Randy Fromm <[email protected]> for this excellent summary of the diode test method.
And here are my results with my DMM set to diode test where a green cell is a passed test and a red cell is a failed test:
[/SIZE][/FONT][FONT=Arial, Helvetica, sans-serif][SIZE=-1]
[/SIZE][/FONT][SIZE=-1]So according to my testing one of the 4 transistors is good, two are train wrecks, and one is marginal.
I tried double checking some of these tests with my other el-cheapo DMM and it came up with different numbers that were higher but basically only changed one lower failing score to a pass on DT1.
Comments? Can I basically mostly have deflection with numbers like these? Or is it a "there's no way you could have deflection with numbers like that" and there's something wrong with my testing or DMM?
[/SIZE]
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