amiga_1081_monitor_repair
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amiga_1081_monitor_repair [2021/07/09 14:23] sausage created |
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| **Please Note: The activities outlined in this article describe working with electronics that convert up to many thousands of volts. It is very easy to touch the wrong thing and cause permanent damage or death. If you are wanting to repair similar monitors yourself, please arm yourself with safety equipment such as an Isolation Transformer, and insulated tools. And read read read all about CRT repair before even attempting anything similar. Your family with thank you.** | **Please Note: The activities outlined in this article describe working with electronics that convert up to many thousands of volts. It is very easy to touch the wrong thing and cause permanent damage or death. If you are wanting to repair similar monitors yourself, please arm yourself with safety equipment such as an Isolation Transformer, and insulated tools. And read read read all about CRT repair before even attempting anything similar. Your family with thank you.** | ||
| - | {{ :repairs:1081:1081-before.jpg?direct&400|}}I've been looking forward to getting this on the bench for a while now. A friend gave this to me a while back when he sold off his Amiga 1000. I didn't know what state it was in. Like most Commodore monitors, these are worth fixing, with composite in TTL RGB and SCART inputs. | + | {{ :repairs:1081:1081-before.jpg?direct&400|}}I've been looking forward to getting this on the bench for a while now. A friend gave this to me a while back when he sold off his Amiga 1000. I didn't know what state it was in. Like most Commodore monitors, these are worth fixing, with composite in, TTL RGB and SCART inputs. |
| First thing to do was check the standard power on test and see if the thing goes bang or puts out any weird noises or smoke. | First thing to do was check the standard power on test and see if the thing goes bang or puts out any weird noises or smoke. | ||
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| The high voltage sound seemed fine, and I appeared to have a raster. The screen was totally white. Or a pale white. Pressing the green button gave the screen the expected green tint. That seemed to show that the various guns are working in the CRT. | The high voltage sound seemed fine, and I appeared to have a raster. The screen was totally white. Or a pale white. Pressing the green button gave the screen the expected green tint. That seemed to show that the various guns are working in the CRT. | ||
| - | I connected up a Playstation 2 composite cable to the CBVS-IN and audio cable to the audio input. The audio worked fine, but screen was still white. This gave an indication that the main board is actually working and processing at least the audio portion. | + | I connected up a Playstation 2 composite cable to the CVBS-IN and audio cable to the audio input. The audio worked fine, but screen was still white. This gave an indication that the main board is actually working and processing at least the audio portion. |
| It also indicated that the power supply was pretty much working. | It also indicated that the power supply was pretty much working. | ||
| - | Trying to rule out the actual CBVS-IN RCA socket, I tried a composite to SCART adaptor and connected the Playstation 2 to the SCART connector. Same result, white screen plus audio. | + | Trying to rule out the actual CVBS-IN RCA socket, I tried a composite to SCART adaptor and connected the Playstation 2 to the SCART connector. Same result, white screen plus audio. |
| Time to open it up and have a poke around. Kidding of course. Once open, it was serious business time. | Time to open it up and have a poke around. Kidding of course. Once open, it was serious business time. | ||
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| {{ :repairs:1081:1081-open.jpg?direct |}} | {{ :repairs:1081:1081-open.jpg?direct |}} | ||
| - | I was amused to see different sized screws. I'm probably not the first person here. Looking at the main board, I'm most definitely not first. There had been some touch up soldering on most of the ICs, and quite a bit on the CBVS-IN socket. | + | I was amused to see different sized screws. I'm probably not the first person here. Looking at the main board, I'm most definitely not first. There had been some touch up soldering on most of the ICs, and quite a bit on the CVBS-IN socket. |
| Before going on, I decided to see if I could fix the actual switch itself. Getting a replacement could take some time and I'd rather have it sorted now. Disassembling the switch took some time. | Before going on, I decided to see if I could fix the actual switch itself. Getting a replacement could take some time and I'd rather have it sorted now. Disassembling the switch took some time. | ||
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| NTSC is noted on the board, but for PAL, the resistor must be slightly moved into the next position on the PCB. | NTSC is noted on the board, but for PAL, the resistor must be slightly moved into the next position on the PCB. | ||
| R232 PAL is 12V one side and 11.7V the other. So that's probably why pin 11 on IC 502 shows nothing because PAL in connected and NTSC is disconnected. They have separate circuits bridged by the R232 safety resistor. | R232 PAL is 12V one side and 11.7V the other. So that's probably why pin 11 on IC 502 shows nothing because PAL in connected and NTSC is disconnected. They have separate circuits bridged by the R232 safety resistor. | ||
| + | |||
| + | In the image below, the orange line is where the R232 is placed for NTSC, and the blue is where the R232 is placed for PAL. | ||
| {{ :repairs:1081:r232-positions.jpg?direct |}} | {{ :repairs:1081:r232-positions.jpg?direct |}} | ||
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| Checking over all the voltage test points I could reach (I got sick of pulling the board in and out for testing), they all seemed to be fairly much in the expected range. And the voltages in the PAL configuration were not marked on the schematic, so I was satisfied that there should be differences in that area. Perhaps the main board was largely fine. | Checking over all the voltage test points I could reach (I got sick of pulling the board in and out for testing), they all seemed to be fairly much in the expected range. And the voltages in the PAL configuration were not marked on the schematic, so I was satisfied that there should be differences in that area. Perhaps the main board was largely fine. | ||
| - | I then noticed that one of the ground solder joints of the CBVS-IN RCA socket had a really bad crack and was lifting from the PCB. Might not be enough to break contact with ground as there were other ground pins, but it looked really dodgy and I didn't notice the damage earlier. | + | I then noticed that one of the ground solder joints of the CVBS-IN RCA socket had a really bad crack and was lifting from the PCB. Might not be enough to break contact with ground as there were other ground pins, but it looked really dodgy and I didn't notice the damage earlier. |
| {{ :repairs:1081:composite-cracked.jpg?direct |}} | {{ :repairs:1081:composite-cracked.jpg?direct |}} | ||
amiga_1081_monitor_repair.1625840594.txt.gz ยท Last modified: 2021/07/09 14:23 by sausage
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