Okay, I've Googled this issue and found little to help me. I'll give you a little background on the monitor and where I am at.
Monitor was repaired by me about 2 months ago. Basically replaced some bad caps and parts in the Low Voltage section along with a few transistors. Deflection board is a 314 model. Monitor was installed in a Tempest but apparently whoever did the installing bent some of the tabs on the bottom of the monitor frame where the transistor leads attach and shorted out the power and some X-side transistors. I replaced all of those, repaired the broken wire, replaced some parts in the LV section again and have the monitor working fine now.......
Except........, I cannot get an image on the bottom half of the screen when you play Tempest on it. The board set is tested good so it is definitely the monitor. Realize of course that the monitor is mounted vertically so if you were to look at it horizontally, there is only the RH side of the screen visible. You can tell the LH side has collapsed to the middle. I have checked, and rechecked and even subbed in the TO3 (bottlecap)transistors even though they tested good with no results. I have checked for cold solder joints on the header pins for the X, Y, and power attachment points on the deflection board and cleaned and reflowed each of them. I have checked for continuity from the transistors all the way to the deflection board. I pulled and tested Q702, Q704, and all the diodes and resistors on that part of the X circuit.
Am I hunting in the wrong area? If you read the FAQ, it describes the area each transistor covers. In order to have the failure I am experiencing, it would require 2 of the bottlecap transistors to fail. That is why I looked at the Negative side of the X circuit. I have read and reread the FAQ and think there my be a type in the section covering the transistors but it may also be that I am reading the schematic incorrectly. It is my understanding that Q706 is responsible for the negative X (LH) side of the image and Q705 is responsible for the positive X (RH). This of course is when viewing the monitor mounted in a horizontal position. Because Tempest is a vertical mount, the transistors still work the same part of the monitor even though the axis are swapped, is that correct. Or, do I need to start troubleshooting the Minus Y-side of the Deflection board in order to find the reason why I have no image on the screen?
Anyone that can shed a little light on this will probably assist countless others. I have never had this much difficulty isolating a problem like this. It is usually a bad bottlecap transistor and poof, I'm done. I will say again, all these transistors are good/new/tested numerous times. While I have repaired a lot of these monitors, I am still learning and still have along way to go in my understanding of these.
I look forward to some interesting discussion.
Monitor was repaired by me about 2 months ago. Basically replaced some bad caps and parts in the Low Voltage section along with a few transistors. Deflection board is a 314 model. Monitor was installed in a Tempest but apparently whoever did the installing bent some of the tabs on the bottom of the monitor frame where the transistor leads attach and shorted out the power and some X-side transistors. I replaced all of those, repaired the broken wire, replaced some parts in the LV section again and have the monitor working fine now.......
Except........, I cannot get an image on the bottom half of the screen when you play Tempest on it. The board set is tested good so it is definitely the monitor. Realize of course that the monitor is mounted vertically so if you were to look at it horizontally, there is only the RH side of the screen visible. You can tell the LH side has collapsed to the middle. I have checked, and rechecked and even subbed in the TO3 (bottlecap)transistors even though they tested good with no results. I have checked for cold solder joints on the header pins for the X, Y, and power attachment points on the deflection board and cleaned and reflowed each of them. I have checked for continuity from the transistors all the way to the deflection board. I pulled and tested Q702, Q704, and all the diodes and resistors on that part of the X circuit.
Am I hunting in the wrong area? If you read the FAQ, it describes the area each transistor covers. In order to have the failure I am experiencing, it would require 2 of the bottlecap transistors to fail. That is why I looked at the Negative side of the X circuit. I have read and reread the FAQ and think there my be a type in the section covering the transistors but it may also be that I am reading the schematic incorrectly. It is my understanding that Q706 is responsible for the negative X (LH) side of the image and Q705 is responsible for the positive X (RH). This of course is when viewing the monitor mounted in a horizontal position. Because Tempest is a vertical mount, the transistors still work the same part of the monitor even though the axis are swapped, is that correct. Or, do I need to start troubleshooting the Minus Y-side of the Deflection board in order to find the reason why I have no image on the screen?
Anyone that can shed a little light on this will probably assist countless others. I have never had this much difficulty isolating a problem like this. It is usually a bad bottlecap transistor and poof, I'm done. I will say again, all these transistors are good/new/tested numerous times. While I have repaired a lot of these monitors, I am still learning and still have along way to go in my understanding of these.
I look forward to some interesting discussion.


